Prediction and Control of Interaction Between Ground Building and Tunnel Construction Process 9811934738, 9789811934735

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Dan Meng · Changfeng Yuan · Guangming Yu

Prediction and Control of Interaction Between Ground Building and Tunnel Construction Process

Prediction and Control of Interaction Between Ground Building and Tunnel Construction Process

Dan Meng · Changfeng Yuan · Guangming Yu

Prediction and Control of Interaction Between Ground Building and Tunnel Construction Process

Dan Meng School of Architectural Engineering Qingdao Agricultural University Qingdao, Shandong, China

Changfeng Yuan School of Civil Engineering Qingdao University of Technology Qingdao, Shandong, China

Guangming Yu School of Civil Engineering Qingdao University of Technology Qingdao, Shandong, China

ISBN 978-981-19-3473-5 ISBN 978-981-19-3474-2 (eBook) https://doi.org/10.1007/978-981-19-3474-2 Jointly published with China Architecture & Building Press The print edition is not for sale in China (Mainland). Customers from China (Mainland) please order the print book from: China Architecture & Building Press. © China Architecture Publishing & Media Co., Ltd. 2022 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publishers, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publishers nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publishers remain neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore

Preface

With the accelerated pace of urbanization in China, the center of people’s life is gradually moving closer to the city. At the same time, the state has vigorously promoted higher education and more and more cities have issued preferential policies to attract the inflow of talents. As a result, the urban population shows explosive growth. The increase of urban population is bound to bring a series of problems, such as the reduction of living space, shortage of water resources, traffic congestion, environmental deterioration, and so on. In order to facilitate citizens to travel and alleviate urban traffic pressure, major cities are speeding up the establishment of a three-dimensional, multi-level and intelligent transportation system. The complicated urban interchange alleviates the urban traffic pressure to a great extent. In this process, people gradually realize that the underground space has great potential for development. As the main body of underground space transportation, urban tunnel has been welcomed by major cities in recent ten years. The successful operation of urban tunnel has relieved the traffic pressure on the urban ground, and its fast and convenient characteristics make the tunnel construction enter the stage of rapid development in recent years. With the rapid development of underground engineering, there are also some problems. Firstly, although the construction of underground engineering provides us with more possibilities to make use of underground space and provides a new method for the improvement of urban traffic, it not only alleviates the bottleneck of the current urban planning and development, and obtains greater economic and social benefits, but also has some adverse effects on our urban living environment. For example, in the process of subway construction, it will cause groundwater redistribution, ground stress concentration, and stratum additional stress, which is reflected in the damage of underground and surface environment, such as the deformation and cracking of road surface, the deformation and destruction of surface buildings, the destruction of underground pipelines and other urban facilities, and the change of underground water system. These damages and environmental damage will become the bottleneck of environmental protection in the process of subway construction.

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Preface

Secondly, with the construction and operation of more and more tunnels, the planned construction projects are inevitably adjacent to or intersected with the tunnel. In order to maximize the use of urban aboveground space, the state vigorously promotes the construction of high-rise buildings. When the foundation pit is excavated, the original stress field and displacement field will be changed due to excavation and unloading. It will affect the safety of the tunnel structure. The influence of foundation pit excavation in the adjacent tunnel on the tunnel has increasingly become one of the scientific research topics that the client, design, construction, tunnel operation, and maintenance departments and scientific research institutions urgently need to solve. At the same time, with the continuation of building construction, the construction loading of the new high-rise main structure and the use stage of the main structure after capping may have an impact on the adjacent existing tunnel, which cannot be ignored. Although relevant scholars have done a lot of research and achieved considerable research results, there are relatively few related studies on the typical soil-rock binary structure geological conditions of “upper soft and lower hard.” Therefore, some areas have issued corresponding management measures, such as stipulating the establishment of safety reserves within a few meters on both sides of the tunnel, and no new construction, expansion, reconstruction, and so on. However, based on these methods, there are often two phenomena: Firstly, engineering designers exaggerate the impact of foundation pit excavation on the existing tunnel, which is conservative in design, resulting in high project cost; secondly, in the process of foundation pit engineering design, design and construction are carried out according to the traditional method, without considering the impact of foundation pit excavation on the adjacent tunnel, which often results in excessive deformation of the tunnel and affects the normal operation of the tunnel. Therefore, in order to solve the above problems reasonably, only by exploring the building damage assessment scheme and protective measures under the influence of tunnel construction which is suitable for specific engineering geological conditions, and considering the key technologies such as the construction impact assessment method and scheme improvement of the building foundation pit and main structure of the existing tunnel, we can provide the solution that the system can be used for reference, which can make more reasonable use of underground space. In order to solve the above problems pertinently, the authors and members of the research group collate and summarize the research results through the accumulation of long-term theoretical research and engineering practice, providing reference for the construction of similar projects. The content of this book is mainly about the theoretical research and engineering case analysis of the influence and control of tunnel construction on existing buildings, as well as the research and engineering practice of the influence and control of construction on existing tunnels. In view of the engineering practice of subway tunnel passing through buildings under typical geological conditions in Qingdao, the methods and means of on-site monitoring, numerical simulation, and theoretical analysis are adopted. In this book, the law of stratum deformation caused by subway tunnel excavation and the damage

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mechanism and law of subway tunnel crossing buildings under typical geological conditions are studied, and the safety risk management of subway tunnel crossing buildings is discussed. Aiming at the problems of excavation and unloading of foundation pit and construction loading of main structure in the construction of high-rise building, the safety evaluation method of adjacent tunnel is explored. Combined with engineering practice, the construction scheme is optimized, the safety of existing tunnel is systematically evaluated, and the control measures are given. It is expected to provide reference for underground engineering construction and high-rise building construction in Qingdao and similar geological conditions. Qingdao, China

Dan Meng Changfeng Yuan Guangming Yu

Contents

1 Summarize . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1 6

2 Basic Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 General Law of Surface Movement Caused by Tunnel Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Analysis of the Influence of Surface Movement and Deformation on Ground Buildings . . . . . . . . . . . . . . . . . . . . . . . . 2.2.1 The Impact of Ground Subsidence on Buildings . . . . . . . . . . 2.2.2 The Impact of Ground Tilt on Buildings . . . . . . . . . . . . . . . . . 2.2.3 The Effect of Surface Curvature on Buildings . . . . . . . . . . . . 2.2.4 The Impact of Ground Surface Deformation on Buildings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Allowable Deformation of the Building . . . . . . . . . . . . . . . . . . . . . . . . 2.4 Yield Proximity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 Concrete Failure Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6 Calculation of Additional Stress in Foundation . . . . . . . . . . . . . . . . . . 2.6.1 Mindlin Solve for Additional Stress of Foundation . . . . . . . . 2.6.2 Calculating Additional Stress of Foundation by Corner Point Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7 Theoretical Calculation of Additional Stress and Displacement of Tunnel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7.1 Theoretical Calculation of Additional Stress and Displacement of Tunnel . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7.2 Theoretical Calculation of Tunnel Displacement . . . . . . . . . . 2.8 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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3 Analysis of Ground Settlement Caused by Subway Tunnel Excavation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Calculation Method of Stratum Subsidence . . . . . . . . . . . . . . . . . . . . . 3.2 Basic Parameter Inversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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3.2.1 Calculation of Settlement Trough Width and Formation Loss Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.2 Determining Basic Parameters of Surface Movement by Back Analysis Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Comparative Analysis and Discussion of Peck Method and Random Medium Theory Method . . . . . . . . . . . . . . . . . . . . . . . . . 3.4 Comparative Analysis Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

32 35 40 42 42 45

4 Analysis of Deformation and Stress of Buildings Under Tunnel . . . . . 4.1 Project Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Stratum Subsidence Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.1 Peck Method Inverse Analysis of Ground Movement Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.2 Random Medium Theory Back Analysis of Ground Movement Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Analysis of Vertical Displacement of Frame-Shear Wall Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.1 Finite Element Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.2 Settlement Conditions Imposed by the Model . . . . . . . . . . . . 4.3.3 Displacement and Stress Analysis of Structures Under Different Working Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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5 Quantitative Prediction Method of Building Damage . . . . . . . . . . . . . . 5.1 Project Overview and Settlement Prediction . . . . . . . . . . . . . . . . . . . . 5.1.1 Project Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.2 Settlement Prediction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Building Structure Damage Prediction Method . . . . . . . . . . . . . . . . . 5.2.1 Yield Proximity Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.2 Analysis of Damage Results of Concrete Building Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 The Impact of Blasting Vibration on Concrete Structure Damage Prediction and Control Standards . . . . . . . . . . . . . . . . . . . . . 5.3.1 Settlement Control Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.2 Blasting Vibration Monitoring Results and Analysis . . . . . . . 5.3.3 Damage Prediction Caused by Building Blasting Vibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.4 Damage Prediction Due to the Dual Effects of Surface Settlement and Blasting Vibration . . . . . . . . . . . . . . . . . . . . . . 5.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

65 65 65 67 70 70

49 50 50 50 50 52 57 63

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Contents

6 Risk Management of Crossing Buildings in Tunnel Construction . . . . 6.1 Risk Management Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.1 Environmental Safety Management Classification of Rail Transit Engineering Construction . . . . . . . . . . . . . . . . 6.1.2 Fundamental Mechanical Problems and Safety Risk Management Objectives of Tunnel Engineering . . . . . . . . . . 6.2 Risk Management System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.1 Pre-construction Investigation and Assessment of the Current Situation of the Building and Risk Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.2 Establishment of Safety Control Standards for Buildings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 Application of Urban Tunnel Crossing Building Risk Management Engineering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.1 Investigation, Inspection and Appraisal of Buildings Along the Tunnel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.2 Relative Position Relationship Between Subway Tunnel and Building . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.3 Building Risk Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.4 Building Settlement Control Standard . . . . . . . . . . . . . . . . . . . 6.3.5 Building Blasting Vibration Control Standard . . . . . . . . . . . . 6.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Law of Ground Movement in Foundation Pit Construction of Adjacent Tunnel Buildings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1 Statistical Analysis of the Influence of Foundation Pit Excavation on Adjacent Tunnels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2 Strata Movement Law Under Typical Geological Conditions in Qingdao . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Key Technologies for Foundation Pit Construction of Adjacent Tunnel Buildings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1 Main Research Steps and Content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2 Construction Technology and Technology of Foundation Pit of Adjacent Built Shallow Buried Tunnel . . . . . . . . . . . . . . . . . . . . . . 8.2.1 Simulation and Analysis of the Influence Process of Foundation Pit Excavation on Tunnel . . . . . . . . . . . . . . . . . 8.2.2 Temporal and Spatial Effect of Foundation Pit Excavation and Influence of Construction Technology . . . . . 8.2.3 New Method of Progressive Step Excavation . . . . . . . . . . . . . 8.3 Evaluation of the Impact of Foundation Pit Construction on the Safety of Adjacent Tunnels . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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89 90 92 92 94 98 104 107 111 113 115 115 138 139 141 141 143 143 151 166 171

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8.3.1 Qualitative and Quantitative Analysis Method for the Influence of Foundation Pit Construction on Adjacent Tunnels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3.2 Safety Impact Assessment Index . . . . . . . . . . . . . . . . . . . . . . . 8.3.3 Assessment Method of Overall Stability of Adjacent Tunnels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4 Research on Monitoring Technology in Foundation Pit Excavation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.1 Location of Monitoring Points . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.2 Monitoring Items . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Impact of High-Rise Construction on Adjacent Existing Tunnels . . . . 9.1 Project Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.2 Establishment of Finite Element Model . . . . . . . . . . . . . . . . . . . . . . . . 9.2.1 Basic Assumptions for Model Establishment . . . . . . . . . . . . . 9.2.2 Selection of Parameters of Each Material Unit in the Model and Setting of Boundary Conditions . . . . . . . . . 9.2.3 Setting of Load Conditions of the Model . . . . . . . . . . . . . . . . 9.2.4 Setting of Model Simulation Conditions . . . . . . . . . . . . . . . . . 9.2.5 MIDAS/GTS NX Model View . . . . . . . . . . . . . . . . . . . . . . . . . 9.3 Analysis of the Influence of Excavation Unloading on Tunnel . . . . . 9.3.1 Analysis of Monitoring Results of Excavation Unloading of Foundation Pit . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3.2 Analysis of Excavation Unloading Numerical Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3.3 Analysis of the Impact of Excavation Unloading on Adjacent Tunnels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4 Impact Analysis of New Building Loading on Adjacent Existing Tunnels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4.1 Deformation Analysis of Surrounding Strata in the Loading Process of New High-Rise Buildings . . . . . . 9.4.2 Deformation Analysis of Adjacent Tunnels in the Loading Process of New High-Rise Buildings . . . . . . 9.5 Influence Analysis of Wind Load on Tunnel After Roof Sealing of New Building . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.5.1 Analysis of the Impact of Northerly Wind Load on Buildings on Tunnels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.5.2 Analysis of the Influence of South Wind Load on the Building on the Tunnel . . . . . . . . . . . . . . . . . . . . . . . . . . 9.5.3 Analysis of the Influence of Westerly Load on the Building on the Tunnel . . . . . . . . . . . . . . . . . . . . . . . . . . 9.5.4 Deformation Under Wind Load . . . . . . . . . . . . . . . . . . . . . . . . 9.6 Influence Analysis of Tunnel Displacement Under Different Building Parameters and Protection Measures . . . . . . . . . . . . . . . . . .

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9.6.1 Impact Analysis of Different Building Heights on Tunnels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6.2 Analysis of the Influence of Different Horizontal Distances Between New Buildings and Adjacent Tunnels on Tunnels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6.3 Protective Measures for Adjacent Tunnels . . . . . . . . . . . . . . . 9.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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234 235 238 240

Appendix A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 Appendix B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 Appendix C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 Appendix D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 Appendix E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309

About the Author

Dr. Dan Meng, male, was born in 1980. He is Associate professor of Qingdao Agricultural University, Master Supervisor, and Postdoctoral Fellow. He is mainly engaged in the research of the theory and practice of urban tunnel construction influence building protection, prefabricated building, green building materials, and so on. He has published more than 40 academic papers, including 14 SCI and EI papers. Dr. Changfeng Yuan is Professor of Qingdao University of Technology, Master supervisor, Member of Chinese Society of Rock Mechanics and Engineering, and Director of Shandong Society of Rock Mechanics and Engineering. He is mainly engaged in underground engineering construction, intelligent civil engineering, engineering deformation monitoring and other work. He presided over and participated in completing three projects of National Natural Science Foundation of China, one key project and two general projects of Natural Science Foundation of Shandong Province and two key science and technology research projects of Shandong Province. He presided over and completed 33 projects including subway construction, BIM technology application of deep foundation pit, engineering deformation prediction, 3D laser scanning application of deep foundation pit, interaction between buildings and tunnels, etc. He has published more than 40 academic papers, including more than 20 SCI and EI papers, nearly 20 authorized invention patents. Dr. Guangming Yu is Professor of Qingdao University of Technology, Doctoral Supervisor, Director of Shandong Engineering Research Center for Rock damage Protection and Surface Subsidence Control, and Former Dean of School of Civil Engineering, Qingdao University of Technology. He is Member of the Fourth Professional Committee of the International Association of Mine Surveying, Deputy Director of the Professional Committee of Rock Physics and Mathematical Simulation of Chinese Society of Rock Mechanics and Engineering, Council Member of Soil Mechanics and Geotechnical Engineering Branch of China Civil Engineering Society and Member of the Professional Committee of Mine Surveying of China Coal Society. He is Editorial Board Member of The Journal of Rock Mechanics and Engineering xv

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About the Author

and Standing Committee Member of the Editorial Board of the Journal of Geological Hazards and Protection of China. He was appointed as an expert directly in charge of organization Department of the Central Committee of the Communist Party of China, an expert in mining damage appraisal of China Coal Association, the chief scientist of “Collaborative Innovation Center of Engineering Construction and Safety in Blue Economic Zone” of Shandong Province, and the chief expert of structural Engineering discipline of Shandong Province. He was awarded the first batch of national candidates of the New Century Talents Project, special government allowance of The State Council, Expert with Special Contribution of Shandong Province, Famous Teaching Teacher of Shandong Province, Excellent Postgraduate Instructor of Shandong Province, Excellent Teacher of Baogang, Model Worker of Qingdao, Excellent Teacher of Qingdao, and so on. He specializes in underground engineering construction, building health maintenance, civil engineering disaster prevention, mining disaster monitoring, and other work. He has published more than 150 papers, including more than 80 SCI and EI papers.

Chapter 1

Summarize

With the accelerated pace of urbanization in China, the center of people’s life is gradually moving closer to the city. At the same time, the state has vigorously promoted higher education, more and more cities have issued preferential policies to attract the inflow of talents. As a result, the urban population shows explosive growth. The increase of urban population is bound to bring a series of problems, such as the reduction of living space, shortage of water resources, traffic congestion, and environmental deterioration and so on. In order to facilitate citizens to travel and alleviate urban traffic pressure, major cities are speeding up the establishment of a three-dimensional, multi-level and intelligent transportation system. The complicated urban interchange alleviates the urban traffic pressure to a great extent. In this process, people gradually realize that the underground space has great potential for development. As the main body of underground space transportation, urban tunnel has been welcomed by major cities in recent ten years. The successful operation of urban tunnel has relieved the traffic pressure on the urban ground, and its fast and convenient characteristics make the tunnel construction enter the stage of rapid development in recent years. With the rapid development of underground engineering, there are also some problems. Firstly, the underground engineering construction gives us more likelihood, providing new methods for urban traffic improvement, alleviating bottleneck problems of major urban planning and development, gaining greater economy and society Benefits, but at the same time also have some adverse effects on our urban living environment. For example, in the construction process, the groundwater will cause groundwater, stress concentration and formation stress [1, 2], which reflect the underground and ground environment, expansive as a road pavement, crack breaking, deformation and destruction of surface buildings, as well as destruction of various urban facilities such as underground pipelines. These facilities damage and environmental damage will become a bottleneck of environmental protection in the construction process of subway engineering. During the construction of a subway tunnel, there have been problems such as different levels of road collapse, build-deformation crack (Figs. 1.1 and 1.2). The cause of the above engineering problem is closely related to © China Architecture Publishing & Media Co., Ltd. 2022 D. Meng et al., Prediction and Control of Interaction Between Ground Building and Tunnel Construction Process, https://doi.org/10.1007/978-981-19-3474-2_1

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Fig. 1.1 Subway tunnel construction caused road collapse

special geological conditions of the region. The formation conditions in the depth of the subway tunnels have changed large, and the tunnel construction process should pass sharply changed flora layers, silt layers, granite, brilliant rock and other special formations, and apply existing construction methods and scientific means to apply In this project construction, in the survey, design, construction management and other links, the slightly deviation will have an accident, especially the construction link is more important in the seriousness of the accident prevention. The total length of Qingdao’s subway tunnel is about 24.9 km, all of which are underground lines, and 22 stations, and the tunnel is relatively shallow (16–25 m). Along the ground is a bustling business district and residential area, the ground building is concentrated, and various structures are buried underground. Therefore, in order to fully consider the impact of urban environment during the construction process of the subway, we need more targeted scientific methods, which will be more clearly recognized by the determination of surface formations caused by the construction of the subway tunnel, and the sedimentation deformation of ground buildings and others. The response of urban facilities on the construction of the subway tunnel. Only in this way, we can effectively take corresponding protective measures to reduce the perturbation of urban environments as much as possible to ensure the normal life order of the city [3, 4]. Secondly, with more and more tunnel construction operations, the construction project of planning and construction is inevitably adjacent or intersected with tunnels. In order to make the city ground space to maximize the maximum use of high-rise buildings, when the new high-rise building is excavated in the foundation pit, due to excavation, the original stress field is caused, and the displacement field changes, which will affect the tunnel structure. Safety. The impact of building foundation pit excavation on the neighboring tunnel is increasingly becoming one of the scientific

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Fig. 1.2 Subway tunnel construction causes cracking in the building

research topics of the entrustment party, design, construction, and tunnel operation and maintenance sector and research institutions [5]. For example, the depth of Shanghai Jinqiao Square is 5–6.9 m, the minimum distance of the bottom of the tunnel vault is only 4 m; the depth of the foundation of the foundation pit of Daning Commercial Center in Zhabei District, Shanghai, and the east side envelope is running subway. The minimum net distance of the tunnel is only 5.45 m. The impact analysis of the foundation pit excavation on the tunnel is 21 outlined the key and accurate evaluation of the class, accurate and reasonable evaluation of the influence of deep foundation pit on adjacent tunnels into important engineering projects in the construction process. At the same time, with the continued operation of the construction project, the construction of the new high-level main structure and the use of the main structure is capped, it is possible to have an impact on adjacent tunnels and cannot be ignored. Although this engineering example is extremely frequent in Shanghai, Beijing, Shenzhen and other regions (Fig. 1.3), and the relevant scholars have also conducted a lot of research, and the research results have been achieved. However, there are relatively few studies on specific rock strata in Qingdao area (Qingdao area is a typical “soil-rock dual structure” with soft upper and hard lower) [6, 7].

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(a)

(b)

Fig. 1.3 Deep base pits adjacent to both tunnels: a Shenzhen deep base pit project; b Shanghai subway station foundation pit project

Due to mutually influential tunnels and high-rise building construction technology difficulty, evaluation methods and means are not reasonable, the relevant departments have launched management methods for the construction of tunnels and rail transportation construction management methods, and management methods respectively stipulate 100 m ranges on both sides of the tunnel. Establish a security area within the protected area shall not be newly built, expanded, rebuilt construction (building), 50 m on both sides of the subway tunnel, is a control protected area, and further refine the special protected area. Based on these methods, it is often caused by two phenomena: First, the engineering design personnel exaggerate the impact of foundation pit excavation on both tunnels. It is more conservative when designing, leading to the project cost; second, in the foundation of the foundation pit, according to the tradition Method for design and construction, regardless of the influence of foundation pit excavation on neighbouring tunnels, there is often an excessive tunnel deformation, affecting the normal operation of the tunnel. Therefore, the above problems are reasonably solved. For a particular geological condition, the construction of building damage evaluation schemes and protective measures under the influence of the tunnel construction of specific engineering geological conditions are explored, and the impact assessment of construction foundation pit and main construction of both tunnels is considered. Key technologies such as methods and program improvements, providing a system for reference to a solution to use the underground space more reasonably. The content of this book is mainly the theoretical research and engineering example analysis of the impact of the tunnel construction on the impact of the existing buildings, and the research and engineering practice of building construction on existing tunnels. Aiming at the engineering practical engineering of a typical geological conditions such as the “Soft hard” earth-binary structure in the Qingdao area, the method and means of on-site monitoring, numerical simulation, theoretical analysis, and the study 31 outline typical geological conditions The ground deformation regulation caused by the excavation of the subway tunnel, the subway tunnel crosses the mechanism and law of building damage, and discusses the safety risk management of the subway

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tunnel through the building. The research content mainly includes the following aspects: 1. Summary Analysis The basic theory of the yield proximity, concrete damage criteria, foundation stress and tunnel addition stress and displacement of the study. 2. Based on the engineering site monitoring data, the PECK method is used to reverse analysis of the sink width caused by the excavation of the metro tunnel, and the land loss rate caused by the discharging of the excavation of the subway station, including the sedimentation slot of the settlement slot as well as the section shrinkage; compare the PECK method and the theoretical method of random media. 3. Taking the subway station as an example to establish finite element model, reverse analysis of surrounding rock parameters; selecting a limited element simulation similar to the geological conditions, verify the surrounding rock parameters, which in turn has a general law of surface settlement. 4. Through finite element analysis, the stress distribution of building structures under the influence of surface settlement and blasting vibration, combined with OTTOSEN and the yielding process of the yield proximity to the criterion of the building structure and evolutionary processes, by This realization of quantitative assessment and control of construction structures cracking damage under different settling amount and blasting vibration speed. 5. From the current status assessment and safety evaluation of the construction, the construction of the tunnel construction scheme is optimized, the construction process control, process monitoring and post-assessment and recovery is subject to the system. Sexual control, constructing tunnel construction crossing safety risk management system. In response to problems such as foundation pit excavation and main structural construction and loading in the construction process of high-rise building, explore the safety evaluation method of the neighbouring tunnel, combined with the engineering practice to optimize the construction plan, the systematic evaluation of both tunnel safety and gives control measures. The main research content includes the following aspects: 1. Statistical analysis of relevant engineering cases at home and abroad, find out the key influencing factors adjacent to the tunnel during the excavation of the building foundation, and simultaneously combine the routine of rock formation under the typical geological conditions, and study the effects of foundation pit excavation on adjacent tunnels. 2. Combined with the engineering example, analyze the mission of the rock formation caused by foundation pit excavation on the evolution of the deformation of adjacent tunnels, the systematic research and optimization of the construction of the construction of the construction of the construction of the construction foundation and construction of the construction of the construction foundation and construction of the construction of the construction of shallow tunnels.

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3. Summary Analysis The evaluation index and evaluation method of the construction of the tunnel safety effect on the construction of the tunnel construction, first, the main factors of the engineering construction on the impact of the tunnel, the overall evaluation; second, analyze the evaluation index, determine the construction Monitoring criteria; Finally, research evaluation methods, facilitating scientific predictions in tunnel safety before construction. 4. According to the means of on-site testing, laboratory test and numerical simulation, R and D is developed adjacent to the construction of the construction of the foundation pit of the tunnel construction and on-site monitoring technology. 5. Combined with MIDAS/GTSNX finite element analysis, research on new highrise buildings in the main structure construction phase, structural capping during construction, the adjacent tunnel deformation caused by the wind load, the influence of the impact law, provides reference for tunnel deformation monitoring.

References 1. Yuan C, Yu G, Zhao Q, Zou J, Guan X (2011) Numerical simulation analysis on impact of surface deformation to the frame-shear wall structure caused by tunnel excavation. Adv Mater Res 243–249 3606–3611 2. Yuan C, Yu G, Wang X, Zhang Y, Guan X (2011) Study on tunnel with subsurface excavation method in urban to damage assessment of underground pipelines. Adv Mater Res 243–249:3582– 3587 3. Yuan C, Yu G, Wang X, Wang N (2012) Chin J Undergr Space Eng 8(5):939–945 4. Yuan C, Yu G, Zhang M, Xu Y, Wang G (2006) Rock and soil mechanics 27(S1):373–376 (in Chinese) 5. Liu D, Tan G, Li Q et al (1999) Chin J Rock Mech Eng 18(2):170–175 6. Zheng M, Yin Z, Wu J et al (2006) Chin J Geotech Eng 28(10):1224–1229 7. Zhang S, Sun R (2006) Application of Fuzzy mathematics in environmental quality assessment: a case study of Tianjin Binhai new area. Environ Sci Manag 31(2):141–142

Chapter 2

Basic Theory

The core content of this book will cover the allowable deformation of buildings, yield proximity, concrete failure criterion, additional stress of foundation and additional stress and displacement of tunnel. This chapter analyzes the calculation method of the influence of tunnel construction on buildings and the loading of new buildings on the existing adjacent tunnels from a theoretical point of view, which provides a theoretical basis for the safety analysis of existing tunnels passing through buildings and adjacent new buildings.

2.1 General Law of Surface Movement Caused by Tunnel Construction In the process of subway tunnel excavation, the original stress balance of the overlying strata is destroyed. If no protective measures are taken, a certain range of rock mass above the strata will fall, and the caving area is called the caving zone. A certain range of rock strata above the caving zone produce cracks and faults along the plane and vertical plane, and the interval where cracks and faults occur is called the fracture zone. The rock strata above the fracture zone until the surface sinks and bends, showing an overall movement, which is called the bending zone or the whole movement zone. The surface points in the upper part of the bending zone move towards the center of the tunnel and form a surface subsidence basin. The above process is collectively referred to as rock movement, and for the surface, it is called surface movement. According to the vector characteristics of surface movement, the movement direction of each point of the surface should point to the central point of the tunnel section, that is, it can be divided into vertical subsidence movement and horizontal movement. The specific quantitative indicators are: vertical subsidence, curvature deformation, tilt deformation, horizontal deformation, horizontal movement, distortion and shear strain, as shown in Fig. 2.1. At present, the law of the first © China Architecture Publishing & Media Co., Ltd. 2022 D. Meng et al., Prediction and Control of Interaction Between Ground Building and Tunnel Construction Process, https://doi.org/10.1007/978-981-19-3474-2_2

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Surface subsidence curve Horizontal displacement curve

Fig. 2.1 Surface movement caused by tunnel excavation

five indexes has been fully studied, but the research on distortion and shear strain is in the initial stage, and it is not widely used. (1)

The subsidence of the vertical

The settlement of a surface point is called subsidence (S). It is expressed by the elevation difference Δ h between this point and the point measured for the first time. The subsidence curve shows the distribution law of subsidence in the surface movement basin, as shown in the curve (1) in Fig. 2.2. (2)

Curvature deformation

The curvature of the section line of the sinking basin is called curvature (K). The average value is expressed by dividing the inclination difference ΔT between two adjacent line segments by the distance between the midpoints of the two line segments, that is, K B = (T AB − TBC )/0.5(AB + BC). The distribution law is: ➀ The curvature curve has a positive curvature area and a negative curvature area, with three extreme values, two equal positive values and one negative value. The positive value is called the maximum positive curvature, located between the boundary point and the inflection point; the negative value is called the maximum negative curvature, located at the maximum sinking point. The shape of the subsidence curve mainly depends on the position of the inflection point of the subsidence curve, and the position of the inflection point is related to the lithology. The harder the lithology, the more the inflection point on the surface subsidence curve is toward the side of the excavation area. ➁ The curvature of the basin boundary point and inflection point is zero, the basin edge area is a positive curvature area, and the central part of the basin is a negative curvature area. Generally speaking, the maximum positive curvature value increases with the increase of the width of the excavation section; the maximum negative curvature value first increases with the increase of the width of the excavation section. Then it changes from large to small, as shown in the curve (2) in Fig. 2.2.

2.1 General Law of Surface Movement Caused by Tunnel Construction

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Fig. 2.2 The distribution law of surface movement and deformation during subway tunnel construction (1) Vertical subsidence curve; (2) Curved Rate deformation curve; (3) inclined deformation curve; (4) horizontal deformation curve; (5) horizontal movement curve

(3)

Tilt deformation

The slope of a sinking basin in a certain direction is called tilt (T ), T AB = S B − S A /l 'AB . Oblique curve represents the change law of the tilt in the basin of the ground movement, and the tilt is the first derivative of the subsidence. The law of the inclined curve distribution is: the inclination from the boundary point of the basin to the inflection point gradually increases, the inclination from the inflection point to the maximum sinking point decreases gradually, and the inclination at the sinking point is zero. The maximum tilt is at the inflection point, and there are two maximum tilts in opposite directions, as shown in curve (3) in Fig. 2.2 shown. (4)

Horizontal deformation

The difference in horizontal movement per unit length between two points in the sinking basin is called horizontal deformation (ε), ε = (μ A − μ B )/AB. When subway tunnel excavation affects the ground surface, if the horizontal movement of each point on the ground surface is unequal, horizontal deformation will occur. There are two types of horizontal deformation of the ground caused by excavation: tension and compression.

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The horizontal deformation curve is the curve (4) in Fig. 2.2. The horizontal deformation curve has three extreme values, two equal positive values and one negative value. The positive value is called the maximum stretch value and is located at the boundary point and the inflection point. Among them, the negative value is called the maximum compression value. It is located at the maximum sinking point. The horizontal deformation at the boundary point and inflection point of the basin is zero. The edge area of the basin is a stretch zone, and the middle of the basin is a compression zone. (5)

Horizontal movement

The displacement of a point in the surface settlement tank along a certain horizontal direction is called horizontal movement (μ), which is expressed by the difference in the horizontal distance from the point to the control point measured this time and the first time, μ = Δl = li − l0 . The distribution characteristics of the horizontal movement are the same as the tilt value, and the movement direction is consistent with the tilt direction. The position where the horizontal movement value is zero is near the maximum sinking point. The horizontal movement curve is the curve (5) in Fig. 2.2. The distribution law is: the horizontal movement from the boundary point of the basin to the inflection point gradually increases, and the horizontal movement from the inflection point to the maximum sinking point gradually decreases, and the horizontal movement at the maximum sinking point is Zero, the maximum horizontal movement at the inflection point, there are two maximum horizontal movement in opposite directions. From the analysis of the above five curves, it can also be seen that the inclined curve and the horizontal movement curve are similar in shape, and the curvature curve and the horizontal deformation curve are similar in shape.

2.2 Analysis of the Influence of Surface Movement and Deformation on Ground Buildings The impact of ground movement and deformation caused by tunnel construction on buildings is related to many factors. In addition to the stratum characteristics, it is also related to the degree of damage to the building, the location of the building, the foundation and structural form of the building, and the deformation of the ground [1]. This kind of damage can be divided into direct excavation damage and indirect excavation damage. The damage suffered by the building located within the tunnel excavation settlement trough is called direct excavation damage. However, sometimes the excavation impact is also found at a location far beyond the scope of the settlement trough of the tunnel excavation. This impact is called indirect excavation damage [2]. Common excavation damage mainly manifests in the following forms.

2.2 Analysis of the Influence of Surface Movement …

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2.2.1 The Impact of Ground Subsidence on Buildings Surface settlement is generally divided into two types: uniform surface settlement and uneven surface settlement. The uniform settlement of the ground causes the building to sink as a whole. Generally speaking, the uniform settlement of the ground does not have much impact on the stability and use conditions of the building. The impact of uneven ground settlement on buildings will be the main research content of this book and will be discussed in detail in later chapters.

2.2.2 The Impact of Ground Tilt on Buildings After the ground is tilted, the skew of the building will cause the center of gravity of the building to shift, generate additional overturning moment, additional stress will be generated inside the bearing structure, and the foundation bearing pressure will be redistributed. This inclination also changes the balance condition of the structural bearing capacity of the building. The wall on the lower side of the inclination is affected by the eccentric force and generates a horizontal shear force. Generally, horizontal shear cracks are generated along the bottom of the wall near the foundation. The slope of the ground causes the building’s ground to have a certain slope, and the ground is easy to accumulate water, which affects people’s normal walking when it is severe. The ground is severely undulating and even the bottom of the building has drainage pipes and sewage backflow, which hinders the normal use of the building. The damage to high-rise buildings caused by the slope of the ground is especially obvious. Excavation of urban underground space will cause uneven settlement of the stratum, and uneven settlement of the stratum will cause the ground surface to tilt, as shown in Fig. 2.3. The slope of the ground has a particularly serious damage to the buildings in the soft soil area. In addition, the slope of the ground has a serious impact on tall buildings with large height and small bottom area, such as chimneys and water towers. The tilt of the ground surface will tilt the center of gravity of

(a)

(b)

Fig. 2.3 The impact of underground excavation on surrounding buildings: a A large amount of water on the ground; b the building is severely inclined

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towering buildings, causing additional stress redistribution, resulting in changes in the internal force of the building structure, and in severe cases, the building will lose stability and damage.

2.2.3 The Effect of Surface Curvature on Buildings Surface curvature has a greater impact on buildings. There are two typical deformation zones for surface curvature: positive curvature deformation zone (the surface is relatively convex) and negative curvature deformation zone (the surface is relatively concave). Under normal circumstances, the surface tensile deformation and positive curvature deformation occur at the same time, and the surface compression deformation and negative curvature deformation occur at the same time. The deformation of the surface curvature indicates the degree of change in the tilt of the surface. Because of the curvature deformation of the surface, the curvature deformation of the surface will change from the original flat shape to the curved shape. In this way, the initial equilibrium state between the load of the building and the reaction force of the foundation soil is destroyed. Under the action of positive and negative curvatures, the contact state of the foundation and the building foundation has two changes. One is that the building is completely cut into the foundation, and the other is that the building partially cuts into the foundation [3], as shown in Figs. 2.4 and 2.5. The building foundation and superstructure will be centered on the contact part. The bending of the ‘hanging area’ causes uneven settlement of the building and the foundation. The force of the building load on the foundation is transferred. At the

Fig. 2.4 Schematic diagram of influence of positive curvature deformation on building foundation

Fig. 2.5 Schematic diagram of the influence of negative curvature deformation on building foundation

2.2 Analysis of the Influence of Surface Movement …

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location, the phenomenon of “hanging” occurs, causing the unloading area to exist in the foundation of the building. Under the influence of positive and negative curvatures, the building will redistribute the reaction force of the foundation, so that the building will have additional bending moment and shear force in the vertical plane. If the value exceeds the strength limit of the building foundation and superstructure, there will be cracks in the building. Under the action of negative curvature, the central part of the building will be suspended. As shown in Fig. 2.4, the wall of the building will have horizontal cracks and positive eight-shaped cracks. When the length of the building is too large, under the action of gravity, the building will break from the bottom, causing damage to the building [4]. Under the action of the positive curvature, the two ends of the building will be partially suspended, as shown in Fig. 2.5. There will be cracks in the wall of the building. In severe cases, the end of the roof truss or beam will be pulled out of the wall or column, causing the building to collapse.

2.2.4 The Impact of Ground Surface Deformation on Buildings The horizontal deformation of the ground caused by the excavation of urban underground space has two types: tension and compression. It has a great destructive effect on buildings, especially the impact of tensile deformation. The ability of buildings to resist tensile deformation is much less than that of compressive deformation ability. Since buildings are very sensitive to the stretching and deformation of the ground, the buildings located in the stretched area of the ground. The bottom surface of the foundation is subjected to the external friction force from the foundation, and the side of the foundation is subjected to the external horizontal thrust from the foundation; and the ability of general buildings to resist tensile deformation is very small, and a small tensile deformation is enough to make the building Cracked. As shown in Fig. 2.6a. The way that the ground surface compression deformation acts on the upper building is also exerted by the pushing force of the foundation to the side of the foundation and the friction force of the bottom surface, but the direction of the force is

Fig. 2.6 Schematic diagram of horizontal deformation damage of buildings: a tensile failure; b compression failure

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opposite to that of stretching. General buildings have greater resistance to compression, that is, buildings are not as sensitive to compression as they are to tension. But if it’s compressed and deformed Large, it can also cause damage to buildings. Moreover, excessive compression will cause crushing damage to the building, and its damage can be more serious than tensile damage, which may cause horizontal cracks in the wall, fold the longitudinal walls, and bulge the roof. This kind of damage is often concentrated in structural weaknesses. For example, sandwiched between two sturdy, Additional buildings between buildings may cause serious damage due to the compression and deformation of the foundation. As shown in Fig. 2.6b. In fact, the destructive effects of surface movement and deformation on buildings are often the result of several deformations, such as the simultaneous occurrence of tension and positive curvature of the ground surface, and simultaneous occurrence of compression and negative curvature.

2.3 Allowable Deformation of the Building Any ground and underground buildings have a certain structural strength and a certain safety factor, that is, they have a certain ability to resist ground displacement and deformation. The allowable deformation of a building means that the deformation of the ground does not affect normal use. It is the allowable value for the building. When the deformation of a building does not exceed the maximum deformation that the building can resist, the building does not show observable damage. Different types of buildings have different abilities to resist deformation due to their different foundation forms and superstructure forms. Therefore, the severity of the consequences after building damage is one of the main factors in the classification of protection levels. At present, our country does not yet have a complete unified classification standard for the protection levels of buildings (structures). The allowable value of surface settlement caused by subway construction in some existing cities is often stipulated by experts based on experience. Such as Beijing Subway. The construction stipulates that the subsidence of any point on the ground shall not exceed 30 mm. Although it is easier to monitor the surface settlement index during construction, this kind of regulation is temporary. Since general buildings are not sensitive to uniform ground settlement, the maximum allowable values of various surface displacements and deformations (vertical settlement, horizontal displacement, ground inclination, curvature and horizontal deformation, etc.) should usually be specified according to the protection level requirements of the protected object. Using only the amount of ground settlement as the only indicator of ground building protection is strict, causing construction difficulties, increasing costs, and sometimes failing to meet the requirements of ground protection. Taking into account the degree of damage to surrounding buildings that may be caused by the ground deformation caused by excavation (Table 2.1), some countries and regions have stipulated the damage level of buildings and the allowable deformation value of buildings (Table 2.2), these values can provide a reference for determining the allowable deformation value of the surface.

2.3 Allowable Deformation of the Building

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Table 2.1 The response of buildings under different settlement differences [5] Building structure type

δ/L (L is the length of the building, δ is the differential settlement)

Building response

1. General brick wall load-bearing structures, including structures with internal frames, with a length-to-height ratio of less than 10; ring beams; natural foundations

Up to 1/150

There are a lot of cracks in the partition wall and the load-bearing brick wall, and the structure may occur Sexual destruction

2. General reinforced concrete frame structure

Up to 1/150

Severely deformed

Up to 1/150

Cracks started to appear

3. High-rise rigid building

Up to 1/250

Observe the tilt of the building

4. Factory building with single-story bent frame structure (natural foundation or pile foundation) with bridge driving

Up to 1/300

Bridge running is difficult, not adjust the level of the rail surface is difficult to run, the separation wall has cracks

5. Sloping frame structure

Up to 1/600

In a safe limit state

6. Machine foundations that are generally sensitive to settlement

Up to 1/850

The machine may have difficulty in use and be at the limit of serviceability

Table 2.2 Allowable deformation values of building foundations in some countries and regions [5] Countries and Regions

Stretch

Compress

Tilt

Curvature

China

2

2

3

0.2

Poland

1.5

1.5

2.5

0.05

Donbass, Soviet Union

2

5

4

0.05

Karaganda

4

4

6

0.33

American

0.4

0.8

3.3

—

Germany

0.6

0.6

1~2

—

France

0.5

1~2

—

—

Japan

0.5

0.5

—

—

England

1.0

1.0

The absolute change of horizontal length is less than 0.03 m

The limit value of urban ground deformation depends on the structure type of the ground structure, the environmental conditions of the structure and the functional requirements of their operation. The deformation limit value generally refers to the uneven settlement rate of the structure. The deformation rate is mainly determined

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according to the three limit states of the structure limit state, the operating limit state and the structural crack limit state. For different buildings, the damage levels are listed in Table 2.3. The excavation of the tunnel disturbs the soil, which may cause uneven settlement of adjacent building foundations, which is the main reason for the deformation of the building. Severe deformation not only affects the normal use of the construction project, but also endangers the safety of the project. My Table 2.3 Building (brick-concrete structure) damage classification [6] Ground deformation prediction value

The damage level that the building may reach

Processing method

≤ 2.0

May not appear on the wall or only a small amount of small width micro cracks below 4 mm are classified as Class I failure

No need to repair

≤ 0.4

≤ 4.0

There may be 4~5 mm No need to repair wide cracks on the wall. The doors and windows are slightly skewed, the wall skin is partially peeled off, and the beam supports are abnormal, which is a level II damage

≤ 10

≤ 0.6

≤ 6.0

There may be 16 ~ 30 mm wide cracks on the wall. The doors and windows are severely deformed, the wall is tilted, the beam head is twitched, and the indoor floor is cracked or bulged, which is a grade III damage

> 10

> 0.6

> 6.0

The wall body will be Must be overhauled, severely inclined, rebuilt or demolished misaligned, externally drum or concave, beam head. The twitch is large, the roof and walls are squeezed out, and there may be a risk of collapse. It is a grade IV damage

Tilt T (mm/m)

Curvature K (mm−1 )

Horizontal deformation U (mm)

≤ 3.0

≤ 0.2

≤ 6.0

Should be medium repair

2.3 Allowable Deformation of the Building

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country’s national standard “Code for Design of Building Foundation” GB500072011 stipulates that the allowable deformation values of building foundations are listed in Table 2.4. Table 2.4 Allowable deformation value of the foundation of the building [7] Deformation characteristics

Foundation soil category Medium and low compressibility soil

High compressibility soil

Local tilt of the foundation of the masonry load-bearing structure

0.002

0.003

Settlement difference between adjacent column foundations of industrial and civil buildings

Framework (L)

0.002

0.003

Side row columns filled with masonry wall (L)

0.0007

0.001

When the foundation settles unevenly. Structure that generates additional stress (L)

0.005

0.005

(120)

200

Settlement amount (mm) of column base of single-layer bent structure (column spacing is 6 m) Inclination of track surface of bridge crane (Consider not adjusting the track)

Portrait

0.004

Horizontal

0.003

Overall tilt of multi-story and high-rise buildings

Hg ≤ 24

0.004

24 < Hg ≤ 60

0.003

60 < Hg ≤ 100

0.0025

Hg > 100

0.002

Average settlement of the foundation of a simple 200 high-rise building (mm) Inclination of the foundation of a towering structure

Settlement of the foundation of a high-rise structure (mm)

Hg ≤ 20

0.008

20 < Hg ≤ 50

0.006

50 < Hg ≤ 100

0.005

100 < Hg ≤ 150

0.004

150 < Hg ≤ 200

0.003

200 < Hg ≤ 250

0.002

Hg ≤ 100

400

100 < Hg ≤ 200

300

200 < Hg ≤ 250

200

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2.4 Yield Proximity In reference [8], in order to study the stability of surrounding rock, the calculation function of yield proximity was derived based on classical strength theories such as Mohr–Coulomb criterion. Yield proximity can be broadly expressed as: the ratio of the parameter describing the current state of a point to the relatively safest state, YAI ∈ [0,1]. Relative to a certain strength theory, it can be defined as: a point in a spatial stress state, the distance from the most unfavorable stress path to the yield surface and the corresponding most stable reference point along the most unfavorable stress path to the yield surface in the same Rod angle direction. The ratio of the distance [9–12]. Assuming that the strength criterion of the rock is the Mohr–Coulomb criterion: √ √ F(σ ) = 1/3I1 sin ϕ + (cos θσ − 1/ 3 sin θσ sin ϕ) J2 − c cos ϕ,

(2.1)

where J 2 —the second deviator stress invariant; I 1 —the first principal stress invariant; ϕ—internal friction angle (°); θ σ —Stress Rod angle (°). √ Formula (2.1) is expressed by the normal stress σπ = I1 / 3 and the shear stress √ τπ = 2J2 on the π plane. And let √ √ √ A = 1/ 3 sin ϕ, B = 1/ 2(cos θσ − 1/ 3 sin θσ sin ϕ), D = −c cos ϕ (2.2a, b, c) F(σπ , τπ , θσ ) = Aσπ + Bτπ + D

(2.3)

In the principal stress space, the stress state at a point A can be expressed as a point on the meridian plane and the π plane, as shown in Figs. 2.7 and 2.8. In the figure, let AA’ and A0 A0 ’ be perpendicular to the EFAO plane, d and D are the lengths of the two respectively, and the coordinates of point A on the meridian plane are (σπ , τπ ), ' and the coordinates of point C are (σπ , τπ ), assuming point A always in the meridian plane, point A0 is always on the isoclinic line, and the coordinate of point C satisfies Fig. 2.7 The stress state at a point on the meridian plane

2.5 Concrete Failure Criteria

19

Fig. 2.8 The stress state at a point on the π plane

formula (2.3). d AC τπ A A' τπ' − τπ = =1− ' = = ' ' D A0 A0 A0 C τπ τπ

(2.4)

Therefore, the yield proximity function is defined as F(σπ , τπ , θσ ) = 1 −

τπ τπ'

(2.5)

According to formulas (2.1)–(2.5), the yield proximity function of the Mohr– Coulomb criterion can be obtained as √ √ √ F(σπ , τπ , θσ ) = [1/ 3I1 sin ϕ + (cos θσ − 1/ 3 sin θσ sin ϕ) J2 √ (2.6) − c cos ϕ]/(1/ 3I1 sin ϕ − c cos ϕ) in the formula, c is the shear strength.

2.5 Concrete Failure Criteria The damage envelope surface of concrete is described by a mathematical function as a condition for judging whether the concrete reaches the damaged state or ultimate strength, which is called the failure criterion or strength criterion [13]. Although it is not a strength theory with clear physical concepts based on mechanical analysis, it is

20

2 Basic Theory

Table 2.5 Concrete failure criteria Failure criterion

Number of parameters

Expression

Guo-Wang rule [13]

5

Kotsovos [14]

5

τ0 = a(b − σ0 /c − σ0 )d )b ( ◦ , θ = 0 , τoct,t = a c − σoct fc ◦

θ = 60 , ξ fc

=a

(

( =d c−

τoct,c fc rc fc √

)2

+b

(

rc fc

)

σoct fc

)e

+ c, r = φrc

Reimann [15]

4

Ottosen [16]

4

a

J2 f c2

Hsieh et al. [17]

4

a

J2 f c2

Podgorski [18]

5

Bresler and Pister [19]

3

2 σoct − c0 + c1 Pτoct + c2 τoct )2 ( τoct σoct σoct fc = a − b fc + c fc

Willam and Warnke [20]

5

θ =0 ,

J2 fc √ + b fJc 2

+λ

◦

τmt fc

+ b If1c − 1 = 0 + c σf1c + d

−1=0 =0

= a0 + a1 σfmc + a2

◦

3

I1 fc

(

σm θ = 60 , τmc f c = b0 + b1 f c + b2 ) ( τm 1 σm f c = r (θ ) 1 − ρ f c

σm fc

(

)2

σm fc

,

)2

a summary of a large number of experimental results and has sufficient calculation accuracy. So far, there are dozens of concrete failure criteria proposed by domestic and foreign researchers. Since the full-scale development of multi-axial test research on concrete, with the accumulation of test data, many researchers have proposed a number of concrete failure criteria based on test results, which are more accurate, but with complex mathematical forms, and there are as many as dozens in total [14–20], their sources are divided into three categories: ➀ borrowing the viewpoints and calculation formulas of classical strength theory; ➁ empirical regression based on concrete multiaxial strength test data; ➂ pure mathematics based on the geometric shape characteristics of the envelope surface derivative. Among them, the more typical applications are listed in Table 2.5. In order to reflect the special geometric shape of the concrete failure envelope, the criterion generally contains 4~5 parameters.

2.6 Calculation of Additional Stress in Foundation When calculating the additional stress of the foundation, it is assumed that the soil is an isotropic and homogeneous linear deformation body, and it extends infinitely in

2.6 Calculation of Additional Stress in Foundation

21

the depth and horizontal directions, that is, the foundation is regarded as a homogeneous and isotropic linear deformation half. Infinite space body, which can be solved directly by applying the theory of elastic half space.

2.6.1 Mindlin Solve for Additional Stress of Foundation The related theory of Boussienesq solution is based on the premise that the load acts on the surface of a semi-infinite space body. For high-rise buildings, the foundation is a deep foundation with a certain buried depth. Regardless of the form of the foundation, the load acts on the interior of the semi-infinite space. Obviously, this is contrary to the conditions for the establishment of Boussienesq’s solution. American Mindlin analyzed the action mechanism of high-rise building foundation on the basis of Boussienesq solution, and deduced the calculation formula of additional stress at any point in the foundation when the load acts on the interior of the semi-infinite space body. It has been verified by engineering practice that the value obtained by Mindlin solution is smaller than the calculated value of Boussienesq solution and is closer to the measured value when solving the additional stress of deep foundation. According to the existing Mindlin theory, when the load Q acts on the internal depth of the semi-infinite body of space at b, as shown in Fig. 2.9, the internal depth of the semi-infinite space body is at any point M (x, y, z). The expression of the normal stress of the base additional stress is: Fig. 2.9 Schematic diagram of the internal load of an infinite half-space body

22

2 Basic Theory

⎡

Q σx = 8π(1 −

3x 2 (z−b) − (1−2μ)(z−b) − (1−2μ)[3(z−b)−4μ(z+b)] R13 R23 R15 ⎢ 30bx 2 z(z+b) ⎢+ ⎢ R27 ⎢ 2 μ) ⎢ + 3(3−4μ)(z−b)x −6b(z+b)[(1−2μ)z−2μb] R25 ⎣ 2 2 4(1−μ)(1−2μ) + R2 (R2 +z+b) × (1 − R2 (R2x+z+b) − Rx 7 ) 2

⎡

Q σy = 8π(1 −

3y 2 (z−b) − (1−2μ)(z−b) − (1−2μ)[3(z−b)−4μ(z+b)] R13 R23 R15 ⎢ 30by 2 z(z+b) ⎢+ ⎢ R27 ⎢ 3(3−4μ)(z−b)y 2 −6b(z+b)[(1−2μ)z−2μb] μ) ⎢ + R25 ⎣ 2 2 4(1−μ)(1−2μ) + R2 (R2 +z+b) × (1 − R2 (R2y+z+b) − Ry 7 ) 2

⎡

σz =

Q 8π(1 −

(1−2μ)(z−b) − (1−2μ)(z−b) R13 R23 1 ⎢ 3(3−4μ)(z+b)z−3b(z+b)(5z−b) ⎢− 5 μ) ⎣ 30zb(z+b)3 R2 − R7 2 3

− − 3(z−b) R5

⎤ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦

(2.7)

⎤ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦

(2.8)

⎤ ⎥ ⎥ ⎦

(2.9)

√ √ where, R1 = r 2 + (z − b)2 , R2 = r 2 + (z + b)2 , r 2 = x 2 + y 2 . Since the Mindlin solution is derived on the basis of the Boussienesq solution, when the load acts on the surface of a semi-infinite body in space, that is, when b = 0, it can be simplified to the Boussienesq solution. σz =

3Pz 3 2π R 5

(2.10)

√ where R1 = r 2 + z 2 . Obviously, the Boussienesq solution is a special case of the Mindlin solution at this time, and its use range is smaller than the Mindlin solution.

2.6.2 Calculating Additional Stress of Foundation by Corner Point Method The method of using the corner point method to solve the additional stress at any point in the soil is as follows: use point P as an auxiliary rectangle, so that point P becomes the common corner point of each rectangle, then the stress at depth z under point P is equal to that of each rectangle. The sum of the stresses caused by the depth. According to the difference of point P, the discussion can be divided into the following situations: (a) When point P is located within the rectangular load surface (Fig. 2.10(1)) σz = (α I + α I I + α I I I + α I V ) p

(2.11)

2.7 Theoretical Calculation of Additional Stress …

23

Fig. 2.10 Schematic diagram of the corner point method to determine the additional stress of the foundation

where p is the average additional pressure of the base ground (kPa); α I , α I I , α I I I and α I V /are the /average additional pressures of the base ground (kPa), get it according to li bi 、z bi (li 、bi is the long side and short side of each small rectangle) and check the specifications. For the situation in Fig. 2.10(2): σz = (α I + α I I ) p

(2.12)

(b) When point P is outside the rectangular load surface (Fig. 2.10(3)) ⏋ ⎡ σz = α(Pebh) + α(Pec f ) − α(Pgah) − α(Pgd f ) p

(2.13)

where α(xxxx) represent the corner additional stress coefficient of rectangle Pebh 、Pecf、Pgah、Pgdf, check the specifications and get them. (c) When point P is located at the midpoint of the rectangular load surface (Fig. 2.10(4)). The processing method at this time only needs to divide the rectangular load surface into four equal parts, and the additional stress σz at point P is four times that of the small rectangle Pabc.

2.7 Theoretical Calculation of Additional Stress and Displacement of Tunnel 2.7.1 Theoretical Calculation of Additional Stress and Displacement of Tunnel Assuming that the soil is a homogeneous soil in a half space, the tunnel is equivalent to an infinitely long homogeneous continuum. Taking the center of the rectangular load as the origin, a new ξ − η rectangular coordinate system is established, and the Mindlin solution is applied in this coordinate system to solve the vertical and horizontal additional stress at any point on the tunnel axis (x1 , y1 , z 0 ) under the action

24

2 Basic Theory

of the uniform load p as: ⎫ ⎧ ˜ ˜ (1 − 2μ)(z 0 − d) ⎡ dξRdη + 3(z 0 − d)3 ⎡ dξRdη ⎪ ⎪ 3 5 ⎪ 1 1 ⎪ ⎪ ⏋⎪ ┌ ⎬ ⎨ 2 ˜ p 3(3 − 4μ)z 0 (z 0 + d) −(1 − 2μ)(z 0 − d) ⎡ dξRdη σz = + 3 2 8π(1 − μ) ⎪ ⎪ ⎪ ˜ − 3d(z 0 + d)(5z 0 − d) ⎪ ⎪ ⎪ ˜ dξ dη ⎭ ⎩ × ⎡ R 5 +30dz 0 (z 0 + d)3 ⎡ dξRdη 7 2

2

(2.14) ⎫ ⎧ ˜ ⎪ ⎪ −(1 − 2μ)(z 0 − d) ⎡ dξRdη + 3(z 0 − d) 3 ⎪ ⎪ ⎪ ⎪ 2 ⎪ ⎪ ˜ y12 dξ dη ⎪ ⎪ ⎪ ⎪ + (1 − 2μ)[3(z − d) − 4μ(z + d)] ⎪ ⎪ ⎡ 0 0 5 ⎪ ⎪ R1 ⎪ ⎪ ˜ 2 ⎪ ⎪ y1 dξ dη ⎪ ⎪ ⎬ ⎨ + 3(3 − 4μ)(z − d) ⎡ 0 5 p R2 ˜ y12 dξ dη σy = ⎪ 8π(1 − μ) ⎪ + 30dz 0 (z + d) ⎪ ⎪ ⎪ ⎪ ˜ ⎡ 2 R25 ⎪ ⎪ ⎪ ⎪ y dξ dη ⎪ ⎪ 1 ⎪ ⎪ ⎡ R 7 + 4(1 − μ)(1 − 2μ) ⎪ ⎪ ⎪ ⎪ 2 ( ) ⎪ ⎪ ˜ 2 2 ⎪ ⎪ y1 y1 1 ⎭ ⎩ ⎡ R2 (R2 +z 0 +d) 1 − R2 (R2 +z 0 +d) − R 2 dξ dη

(2.15)

2

where d is excavation depth for the foundation pit, μ is Poisson’s ratio of soil, ⎡ is integration area for double integration. R1 =

√

(x1 − ξ )2 + (y 1 − η)2 + (z 0 − d)2 ; R2 =

√

(x1 − ξ )2 + (y 1 − η)2 + (z 0 + d)2 .

2.7.2 Theoretical Calculation of Tunnel Displacement When carrying out the theoretical analysis and calculation of the tunnel displacement, the Winkler foundation model is used to calculate the tunnel displacement. From the Winkler foundation model, we can see that the tunnel is regarded as an elastic foundation beam in the calculation. We make the following assumptions: The soil is a homogeneous elastic body in a half-space, and the interaction between the tunnel and the foundation soil is simulated by continuously distributed springs. The contact between the two is elastic contact, the contact surface does not separate from each other, and the deformation satisfies the deformation coordination condition. Therefore, the following mechanical equations are established EI

d 4 w(x) + K w(x) = p(x) dx4

(2.16)

where: w(x) is the horizontal or vertical displacement of the tunnel; p(x) is the additional load on the upper part of the tunnel, vertical load pz (x) = σz D, horizon load p y (x) = σ y D, σz 、σ y are calculated by (2.14) and (2.15), D is the outer diameter

References

25

of the tunnel; EI is the equivalent bending stiffness of the tunnel; K is the coefficient of the foundation bed. Integrate formula (2.16) to get the final tunnel displacement formula as follows: λ w(x) = 2K

(+∞

p(ξ )e−λ|x−ξ | [cos(λ|x − ξ |) + sin(λ|x − ξ |)]dξ

(2.17)

−∞

2.8 Conclusion This chapter summarizes and analyzes the basic theories needed for the calculation of the influence of the tunnel construction on the building and the construction loading of the new building on the existing adjacent tunnel, which provides a theoretical basis for the safety analysis of the existing tunnel when the tunnel passes through the building and the adjacent new building.

References 1. Lei Z, Luo C (2000) Calculation of additional force of building caused by surface deformation and design of anti-deformation structure. Coal Mine Mining 1 2. Zhang M (2007) Research on urban underground space development plan coordinated with environment. Qingdao Technological University, Qingdao 3. Guo W (2005) Research on dynamic influence of underground mining on surface buildings. Liaoning Technical University, Liaoning 4. li B (2007) Research on influence law of tunnel construction and operation on building. Tongji University, Shanghai 5. Yang J (2002) Surface movement and deformation caused by urban tunnel construction. China Railway Publishing House, Beijing 6. National Standard of the People’s Republic of China (2012) Code for design of building foundation (GB50007-2011). China Architecture and Building Press, Beijing 7. National Standard of the People’s Republic of China (2012) Gb50007-2011 code for design of building foundation. China Architecture and Building Press, Beijing 8. Zhou H, Zhang C, Feng X et al (2005) Chin J Rock Mech Eng 24(17):3083–3087 9. Zheng Y, Shen Z (1998) Principle of geotechnical plastic mechanics. Logistic Engineering University Press, Chongqing 10. Xu B, Liu X (1995) Applied elastoplastic mechanics. Tsinghua Fanxue Press, Beijing 11. Xiaonan G (2001) Soil plasticity mechanics. Zhejiang University Press, Hangzhou 12. Maier G, Hueckel T (1979) Nonassociated and coupled flow rules of elastoplasticity for rocklike materials. Int J Rock Mech Mining Sci Geomech Abstracts 16(2):77–92 13. Zhenhai X (2003) Principle and analysis of reinforced concrete. Tsinghua University Press, Beijing 14. Kotsovos MD (1979) A mathematical description of the strength properties of concrete under generalized stress. Mag Concr Res 31(108):151–158 15. Reimann H (1965) Kritische Spannungszustände des Betons bei mehrachsiger ruhender Kurzzeitbelastung. Deutscher Ausschuss fur Stahlbeton, Heft 175, Berlin

26

2 Basic Theory

16. Ottosen NS (1977) A failure criterion for concrete. J Eng Mech Div 103(4):527–535 17. Hsieh SS, Ting EC, Chen WF (1979) An elastic-fracture model for concrete. In: Proceedings of the 3rd engineering mechanics division, special conference. ASCE, Austin, pp 437–440 18. Podgórski J (1985) General failure criterion for isotropic media. J Eng Mech 111(2):188–201 19. Bresler B, Pister KS (1958) Strength of concrete under combined stresses. J Am Concr Inst 55(9):321–345 20. Willam KJ, Warnke ED (1975) Constitutive model for the triaxial behavior of concrete. In: Proceedings of International association for bridge and structural engineering, vol 19. ISMES, Bergamo, pp 1–30

Chapter 3

Analysis of Ground Settlement Caused by Subway Tunnel Excavation

This chapter combines the problem of excessive surface settlement caused by the excavation of a subway station. First, based on the measured data of the station’s surface settlement, the Peck method is used to obtain the settlement trough width and stratum loss rate caused by the station excavation, and the surface settlement trough is fitted. Suggestions are given for the calculation expression of the width of the surface settlement trough caused by the excavation of the subway station. Secondly, the random medium theory method is used to back-analyze the surface movement parameters caused by the initial excavation of the subway station, including the influence range of the settlement trough and the area reduction rate, and the obtained parameters are used to predict the surface settlement of the further excavation of the station. On this basis, based on the comparative analysis of the Peck method and the random medium theory method, the difference in the calculation results of the impact range of the two methods on the surface subsidence is obtained; in order to further verify the correctness of the conclusion, the back analysis method is used to obtain The parameters of surface movement caused by tunnel excavation in some cities in our country, and the angle of influence of the excavated stratum is converted into the width of the settlement trough, compared with the existing calculation results.

3.1 Calculation Method of Stratum Subsidence 1. Peck method In 1969, Peck systematically proposed the concept of stratum loss and a practical method for estimating ground subsidence caused by tunnel excavation [1], that is, the Peck formula ) ( X2 S(X ) = Smax exp − 2 2i © China Architecture Publishing & Media Co., Ltd. 2022 D. Meng et al., Prediction and Control of Interaction Between Ground Building and Tunnel Construction Process, https://doi.org/10.1007/978-981-19-3474-2_3

(3.1)

27

28

3 Analysis of Ground Settlement Caused by Subway …

Point of inflection

Negative curvature

Positive curvature

Tunnel cross section

Fig. 3.1 Lateral surface settlement curve [1]

A · Vi A · Vi Smax = √ ≈ 2.5i i 2π

(3.2)

In the formula, S(X)—the surface settlement value at X from the center axis of the tunnel; V l —stratum loss per unit length of the tunnel caused by construction; S max —the maximum settlement of the ground surface at the centerline of the tunnel; A—cross-sectional area of tunnel; iy —the width coefficient of the surface settlement trough. Peck believes that under undrained conditions, the volume of the surface settlement trough formed by tunnel excavation should be equal to the volume of formation loss [1]. Assuming that the ground loss is evenly distributed over the entire length of the tunnel, the lateral distribution of surface settlement caused by tunnel construction is approximately a normal distribution curve, as shown in Fig. 3.1. For a tunnel with a circular cross-section, Eq. (3.1) becomes: / Smax = 0.313Vl · D 2 i y .

(3.3)

where D—the diameter of the circular tunnel; iy —the horizontal distance from the ground point corresponding to the centerline of the tunnel to the inflection point of the settlement curve General. It is called ‘settlement trough width’. For decades, many scholars have proposed different calculation formulas for the calculation of the width of the settlement trough. The most widely used method is the one proposed by O’Reilly and New (1982) based on the experience of the London area. They believe that i and the buried depth of the tunnel axis z0 following simple linear relationship.

3.1 Calculation Method of Stratum Subsidence

i y = K z0

29

(3.4)

In the formula, K is the width parameter of the settlement tank. Substituting Eqs. (3.3) and (3.4) into Eq. (3.1), a practical engineering formula for estimating the lateral settlement of natural ground can be obtained. ⏋ ┌ 0.313Vl · D 2 y2 S(y) = exp − K · z0 2(K z 0 )2

(3.5)

Figure 3.2 shows the surface settlement curve of different formation loss rates (settlement trough width coefficient K = 0.5) when the ratio of buried depth to section radius of a certain tunnel is 5%) of the surface settlement curve (Fig. 3.3). 2. Random medium theory calculation method Liu [2] and others introduced the concept of random medium theory of foreign stratum deformation, conducted a systematic study on stratum deformation caused by tunnel construction in my country, and formed a complete stratum deformation prediction method. As shown in Fig. 3.4, assuming that the center of any section of underground excavation is at a depth H from the ground surface, the excavation Fig. 3.2 Surface subsidence curves different formation loss rate

Fig. 3.3 Surface settlement curves of different settlement trough widths

30

3 Analysis of Ground Settlement Caused by Subway …

Fig. 3.4 Schematic diagram of tunnel excavation of arbitrary cross section [2]

section will cause the surrounding rock mass to shrink and deform, and eventually the ground will undergo deformation such as settlement and horizontal displacement due to ground loss. According to the random medium theory, the ground settlement at a horizontal distance X from the center of the tunnel can be expressed as: ¨ S(X ) = SΩ (X ) − Sω (X ) = Ω−ω

┌ ⏋ tan β π tan2 β 2 exp − dξ dη − ξ (X ) η η2

(3.6)

In addition, after the ground loss caused by tunnel excavation is reflected on the ground, there is not only ground settlement, but also the horizontal displacement U(X) of the ground surface, the inclination T (X) of a certain point on the ground surface caused by uneven settlement, and the uneven horizontal displacement. The resulting horizontal deformation E(X) at a certain point on the surface can be expressed as Formulas (3.7), (3.8) and (3.9), respectively. dW (X ) = U (X ) = dX dW (X ) T (X ) = = dX

¨ Ω−ω

¨

Ω−ω

⏋ ┌ tan β π tan2 β 2 (X − ξ ) exp − (X − ξ ) dξ dη η2 η2

(3.7)

⏋ ┌ −2π tan3 β π tan2 β 2 (X − ξ ) exp − (X − ξ ) dξ dη η3 η2 (3.8)

dU (X ) E(X ) = dX ┌ ⏋ ┌ ⏋ ¨ tan β 2π tan2 β(X − ξ )2 π tan2 β 2 = 1 − exp − dξ dη − ξ (X ) η2 η2 η2 Ω−ω

(3.9)

3.2 Basic Parameter Inversion

31

Fig. 3.5 The curve of surface deformation predicted by random medium theory: a surface settlement curve; b surface horizontal displacement curve; c surface slope deformation curve; d surface horizontal deformation curve

In the study of the impact of ground subsidence on buildings, sometimes the curvature of a certain place on the surface is also concerned. As shown in Formula (3.10), the curvature is particularly important for buildings that are sensitive to bending. d 2 W (X ) K (X ) = d X2 ⏋ ┌ ┌ ⏋ ¨ 2π tan3 β 2π tan2 β π tan2 β 2 2 = (X − x) − 1 exp − (X − x) d xdz z3 z2 z2 Ω−ω

(3.10) The meaning of the symbols in the formula is shown in Fig. 3.4. Figure 3.5 shows the surface deformation curve of a tunnel when the ratio of buried depth to section radius is 6, the contraction radius is 0.1 m, and the different angles of influence.

3.2 Basic Parameter Inversion A subway station is designed by undercutting method and constructed by drilling and blasting method. The total length is 247 m, the width is 20.6 m, the height is 15.5 m, the buried depth of the vault is 9.3–10.5 m, and the overburden is 2.8–6.4 m. The

32

3 Analysis of Ground Settlement Caused by Subway …

Fig. 3.6 Main section design and excavation method of the station

research object of this chapter is the main section of the station, which is designed as a large arch-foot thin-sided wall structure. It adopts the double-sided pilot tunnel method (arch part) and sub-step method (lower part) construction. The design and construction excavation methods are shown in Fig. 3.6. The geology of the section where the main body of the station is located is characterized by typical “soft top and hard bottom” strata. From top to bottom, they are filled with soil (0.5–2 m), silty clay (1–4.8 m), and sand-bearing cohesive soil (0.9– 2.3 m), strong weathering (4–5 m), moderate weathering (0.6–7.1 m) and slightly weathered granite. The main excavation surface of the station is mainly strongly weathered granite, and the lower part of the main body of the station is mainly medium weathered and lightly weathered granite. Due to the various overlying stratums, it is difficult to consider the influence of specific stratum conditions in the determination of parameters in the study of surface subsidence. According to the section size and buried depth of the main body of the station, it belongs to a shallow-buried large-section tunnel. The strata in the construction affected area are relatively similar. Therefore, the discussion here is not limited to specific strata, and the research conclusions obtained are applicable to the excavation of shallow-buried large-section tunnels in this area. At the beginning of the survey, a large amount of monitoring data of the main body of the station was collected, and finally five sections with relatively complete data were selected to study the basic laws of surface movement.

3.2.1 Calculation of Settlement Trough Width and Formation Loss Rate The Peck method is used to predict or fit the surface settlement. The width of the surface settlement trough i reflects the extent of the impact of the excavation on the surface, and the formation loss rate Vl reflects the extent of the excavation disturbing the formation. It can be seen from Formula (3.2) that these two parameters can completely determine the shape of the lateral surface settlement trough. The ground

3.2 Basic Parameter Inversion

33

subsidence measured data of five sections of the subway station is selected for fitting, and the general law of the ground subsidence trough caused by the excavation of the subway station is studied and analyzed. The fitting function is the Gaussian distribution function (Eq. 3.1), and the fitting parameter is the distance of the recurve point. The specific process of fitting is as follows: ➀ Draw an X-S scatter diagram of all measuring points on the same section, the abscissa is the square of the horizontal distance between the measuring points and the center line of the tunnel, and the ordinate is ln(S/Smax ); ➁ The linear fitting is performed, and the fitting parameters are extracted, that is, √ a straight line. Slope ζ ; ➂ Calculate the settlement trough width i by formula i = −1/ζ ; ➃ Calculate the excavation area, and calculate the formation loss rate Vl by Formula (3.2); ➄ According to Formula (3.1), the surface settlement trough curve can be obtained, and the fitting result is shown in Fig. 3.4 Shown. It can be seen from Fig. 3.4 that the use of Gaussian distribution curve for fitting can better reflect the lateral ground settlement caused by tunnel excavation. During the fitting process, the excavation area of the arch is calculated as 81.1 m2 according to Fig. 3.7 From the fitting results in Fig. 3.7, the i values of the first three sections are all around 6.5 m, with an average value of 6.51 m. The width of the settlement troughs of the latter two sections is larger, and the i value exceeds 10 m. This is mainly because the time for the excavation section to pass through the two sections is relatively short, the surface settlement rate is relatively high, and the ground surface has not reached a stable state. This is clearly shown in the cumulative settlement-time curve of the measuring point in Fig. 3.5. In Fig. 3.5, DC 75~DC 79 belong to Sect. 3.4, and DC80 ~ DC84 belong to Sect. 3.5. Since the surface settlement above the first three sections (Sects. 3.1, 3.2 and 3.3) has reached a stable state, the cumulative settlement curve of the relevant measurement points over time is not given here. At present, the main expression of the width of the settlement trough considering the influence of the width of the tunnel excavation is shown in Table 3.1 (the buried depth of the tunnel, and the span of the tunnel). Since the research object of this chapter is a subway station, the excavation span is relatively large and the relative buried depth is relatively shallow, so the influence of the excavation span should be considered in the calculation of the value. Table 3.1 shows the calculation results of several expressions of the subway station, and also gives the average of the fitting results of the first three sections of the subway station. It can be seen from the comparison result that using the formula i /R = (H/2R)n , when n = 1.0 the calculation result is the closest to the value fitting result of the unique stratigraphic conditions in the area (Fig. 3.8).

34

3 Analysis of Ground Settlement Caused by Subway …

Fig. 3.7 Fitting results of surface settlement troughs at different cross-sections: a cross sections 1; b cross section 2; c cross section 3; d cross section 4; e cross section 5 Table 3.1 Different calculation formulas of settlement trough width i Source and basis

Formula (H/2R)n

n=

Suitable situation

Result

All soil

7.23–6.625

Peck [1] (measurement date)

i /R = 0.8–1.0

Loganathan and Poulos [3]

i /R = 1.15(H/2R)0.9

Cohesive soil

7.96

Atkinson and Potts [4] (measure and model)

i = 0.25(H + R)

Pine sand

5.89

i = 0.25(1.5H + 0.5R) Dense and super-consolidated clay

6.26

This research

Measured data fitting

6.51

The research object is the strata

3.2 Basic Parameter Inversion

35

Fig. 3.8 Cumulative settlement-time curve at the measuring point

3.2.2 Determining Basic Parameters of Surface Movement by Back Analysis Method Assuming that the ground surface of the tunnel construction is stable, the ground subsidence at the actual measurement point is Si0 , and the ground subsidence calculated according to the random medium theory calculation formula is Si . Define the objective function F(x) as F(x) =

m Σ

(Si0 − Si )2

(3.11)

i=1

where m is the number of survey points for ground subsidence, x = {tan β, ΔA}. Using the method of back analysis to determine the surface movement parameters is to find a set of parameters, and through optimization calculations, the objective function value can be minimized. In this book, the adaptive genetic algorithm is used in the optimization calculation, which is an optimization algorithm based on the population hierarchy [5]. The adaptive genetic algorithm is generally expressed as

36

3 Analysis of Ground Settlement Caused by Subway …

GA(et , Jt , St , Ct , Mt , Σt )

(3.9)

where et —Encoding format used by the t-th algorithm; Jt —The fitness measure used by the t-th generation algorithm: St —The selection operation adopted by the t-th algorithm; Ct —The crossover operation adopted by the t-th algorithm; Mt —Mutation operation adopted by the f t-th algorithm; Σt —System parameters used by the t-th algorithm. The operation process of the optimization algorithm is as follows: Step 1 Optimize parameter x = {tan β, ΔAs } coding. Step 2 Initialization: Determine the population size N, crossover probability Pc , mutation probability Pm , and set the termination evolution criterion; − → randomly generate N individuals as the initial population X (0), set t ← 0. Step 3 Individual evaluation: Calculate or evaluate the fitness of each individual in − → X (t). Step 4 Population evolution: I

Selection, use the selection operator from 5 to select the M/2 pair of matrix (M ≥ N ); II Crossover, for the selected M/2 pairs of mothers, perform crossover according to the probability Pm to form M intermediate individuals; III Mutation, perform mutation on M intermediate individuals independently according to the probability Pc to form M candidate individuals; IV Selection, from the M candidate individuals formed above, select N individuals according to their fitness to form a new generation population − → X (t + 1). Step 5 Step 5 Termination test: If the termination criterion has been met, the indi− → vidual with the greatest fitness in X (t + 1) output as the optimal solution, the calculation is terminated. Otherwise, set t ← t + 1 and go to step 4. According to the optimization algorithm, it can be compiled into an anti-analysis program for calculation. Here, the calculation of surface settlement Si uses Formula (3.1), and the integration interval is directly integrated by the method of slicing. Use MATLAB to compile the anti-analysis program INANA.m [6] (see Appendix A for the program). In order to verify the correctness of the program, the calculation example ‘Beijing Subway Fuxin men Turn back Line Project’ in reference [7] is selected for calculation, and the results are compared with the literature results. For a detailed description of the example, see reference [6]. It should be noted that the calculation of surface settlement in the reference is the double integration of Formula (3.6), and the Legendre–Gauss quadrature method is used for numerical integration. The results of the inverse analysis of tanβ and ΔA, this method is 1.393, 15.80 mm, and literature [7] is 1.521, 15.60 mm.

3.2 Basic Parameter Inversion

37

Fig. 3.9 Comparison and verification of the prediction curve of the anti-analysis results

Figure 3.9 shows the comparison between the calculation results of the method and the literature results. The “settlement prediction curve” in the figure shows the surface settlement trough curve obtained by the Legendre–Gauss quadrature method for the inverse analysis parameters of the method. The “calculated value of the inverse analysis program” is the surface settlement, Si obtained by directly integrating the slicing method on the integration interval. The posterior difference test method of reference [7] is used to evaluate the effect of the back analysis. The small error probability P of this method and the reference is 1; and the posterior difference ratio of this method is CY C = 0.133, which is smaller than the reference CY C = 0.145, indicating that the back analysis effect of this method is better than that of references. The difference between the back analysis results of this method and the reference [7] is mainly because the theoretical calculation of surface settlement in the reference analysis uses the same numerical integration method, which leads to the accumulation of errors. The excavation part of Sect. 3.2.1 of the subway station is equivalent to the arched part of the horseshoeshaped section, and the section is uniformly contracted by ΔA I , and the Formula (3.6) can be transformed into: (b (d S(x) =

s(x, ξ, η)dξ dη − a

where: s(x, ξ, η) =

( f (h

tan β η

c

s(x, ξ, η)dξ dη e

(3.13)

g

β exp[− π tan (x − ξ )2 ], a = H − C/2, b = H + C/2, η2 2

/ c = − RG2 − [H − η − C/2 + RG ]2 , d = −c, RG = C/2 + 4R 2 /8C, e = H − C/2 + ΔA I ,

f = H + C/2 − ΔA I ,

√ g = − (RG − ΔA I )2 − [H − η − C/2 + RG ]2 , h = −g

38

3 Analysis of Ground Settlement Caused by Subway …

Table 3.2 Back analysis parameters of surface settlement Section

tan (β)

ΔA I (mm)

1

1.4919

22.70

i R (m) 7.552

i (m) 6.639

2

1.4307

26.80

7.688

6.784

3

1.4344

21.70

7.679

6.111

4

0.8168

21.40

10.608

11.245

5

0.8825

18.40

10.126

10.313

where: X the distance from the settlement point to the centerline of the tunnel; C the height of the arched section; ΔA I The section shrinkage of arch excavation; RG parameters. For this integration interval, five sections are selected for back analysis of surface movement parameters. The back analysis results of each section are shown in Table 3.2. In Table 3.2, the symbols i R and i are the width of the settlement trough calculated by the random medium theory back analysis method and the Peck method, respectively. The prediction results of the surface settlement of the cross-section using the back analysis parameters of each cross-section are shown in Fig. 3.10. It can be seen from Fig. 3.10 that the prediction of surface settlement using the parameters of the back analysis is in good agreement with the measured value of settlement. The Si calculation result of the back analysis is basically the same as the settlement prediction result. It can also be seen from the figure that the prediction result of the inverse analysis program in this section is less than the measured value at the maximum settlement value. Through analysis, it is found that this is mainly due to the large excavation span of the station and the relatively shallow buried depth. At the same time, the uniformly contracted section convergence mode is adopted, which results in the prediction result at the center of the settlement trough being smaller than the measured value. This phenomenon has been confirmed by the results of the literature [8]. From the analysis in the previous section, it can be seen that in the five sections analyzed in this chapter, the surface settlement of the latter two sections has not reached a stable state, which is consistent with the back analysis results of the Peck method. The inverse analysis result of random medium theory also shows that the influence angle of the latter two sections is smaller, that is, the width of the settlement trough is larger, as shown in Table 3.2. Because the subway station currently only completes the construction of the top arched section, and the surface settlement value is relatively large. Therefore, on the basis of the above-mentioned back analysis results, this section uses the back analysis parameters of the arch section excavation to predict the surface settlement results of the subway when the further construction is completed. For the same cross-section of the same tunnel, the parameter tanβ can adopt the value obtained through the back analysis of the measured data of the arch excavation. As for the parameter ΔA, it is a comprehensive reflection of construction conditions.

3.2 Basic Parameter Inversion

39

Fig. 3.10 Prediction curve and measured value of back analysis results of each section of the tunnel: a Cross section 1; b cross section 2; c cross section 3; d cross section 4; e cross section 5

Due to the different excavation area of the arch and the lower part, the value must be different under the same construction method. The specific parameters can be obtained according to the proportional relationship between the excavated area of the arch and the area of the lower excavation. As shown in Fig. 3.6, assuming that the excavation area of the lower part of the station section is A I I after step ➀ ➁ ➂ is completed, and the excavation area after step ➃ ➄ ➅ is completed is A I I I , then the section shrinkage in these two cases can be expressed as: ΔA j = ΔA I · A j /A I , ( j = I I, I I I )

(3.14)

According to Fig. 3.6, it can be calculated that A I I and A I I I are 171.2 m2 and 261.4 m2 respectively, and the corresponding A I I and A I I I are 42.21 mm and 55.68 mm. The prediction results of ground subsidence are shown in Fig. 3.11. It can be seen from Fig. 3.11 that under the same construction conditions, when the excavation in the middle of the station section is completed, the maximum

40

3 Analysis of Ground Settlement Caused by Subway …

Fig. 3.11 The prediction curve of the surface settlement of the tunnel section at different excavation stages

surface settlement value is about 95 mm; after the excavation of the entire section is completed, the maximum surface settlement will be greater than 130 mm. Combining with the aforementioned environmental conditions around the surface of the station, it can be known that surface settlement will have a great impact on the surrounding environment, including buildings, roads and underground pipelines. Therefore, this section recommends that the following measures be taken in the subsequent section excavation construction process: ➀ The design and construction parties should fully understand the importance of the initial support during the construction process, and improve the initial support as much as possible according to the design requirements. Timeliness and effectiveness; ➁ Strengthen the waterproof design to minimize the soil consolidation caused by water seepage and water leakage; ➂ During the drilling and blasting method, the excessive over-excavation phenomenon and the repeated disturbance of the same surface by multiple blasting should be avoided as much as possible.

3.3 Comparative Analysis and Discussion of Peck Method and Random Medium Theory Method From Eq. (3.2), we can see that the physical meaning of Vl A is the convergence area after tunnel excavation (that is, the reduction of tunnel excavation area). In the Peck method, if the tunnel excavation area is assumed to be dξ dη (and completely collapsed), the convergent area should be dξ dη. In this case, the Peck method is a special case of the random medium theory method. That is to say, for the surface settlement caused by a sufficiently small excavation unit, the distribution characteristics of the settlement trough obtained by the random medium theory and the Peck method will tend to be the same. If the two use the same settlement trough width, the Formula (3.15) Is established, the specific settlement calculation results are also consistent. The symbol r(H) in Formula (3.15) means the main influence radius of the excavation of the micro element dξ dη at the center of the tunnel on the ground surface, as shown in Fig. 3.12. The so-called “sufficiently small excavation

3.3 Comparative Analysis and Discussion of Peck Method and Random …

41

Fig. 3.12 The main influence range and influence angle of surface settlement

unit” can be understood in engineering as: corresponding to its excavation radius or excavation area, its buried depth is large enough. The analysis shows that the Peck method is suitable for the case where the buried depth of the tunnel is large and the tunnel excavation area is small. It is an approximation of the random medium theory method in the case of the large buried depth of the tunnel, and is not suitable for the case of ultra-shallow burial. r (H ) =

√ 2πi

(3.15)

For a single-hole tunnel, the initial span of the excavation section is L, and the main influence radius of the ground surface can be expressed as R(H ) = H/ tan β + L/2

(3.16)

In this case, the corresponding surface settlement trough width is √ i R = (H/ tan β + L/2)/ 2π

(3.17)

From the above formula, when the excavation section is small enough, the influence of the tunnel span can be ignored, Formula (3.17) is equivalent to Formula (3.15). However, when the excavation section is large, the influence of the excavation span cannot be ignored. Theoretically, the difference between iR and i should be L/2, but in fact, the Peck method also considers the influence of the excavation area when calculating Vl , so the relationship between the two is difficult to obtain through simple calculations. This conclusion can also be confirmed by the analysis results of the two methods in this chapter: after the surface settlement is stabilized, the iR calculated according to the influence angle of the random medium theory is greater than the i value, but the difference is not half of the excavation span, see Table 3.2.

42

3 Analysis of Ground Settlement Caused by Subway …

3.4 Comparative Analysis Example In order to verify the conclusion of the previous section, in this section, based on the current measured data of surface settlement caused by tunnel excavation in many cities in China, the inverse analysis procedure of this book is used to obtain the tangent tan(β) of the impact angle of surface settlement, and at the same time, according to Formula (3.17) Obtain the i R value, which is listed in Table 3.3. It can be seen from the calculation results that the i R values are all greater than the i value obtained by the direct fitting of the Peck formula in the literature [8]. But the difference between them is not half of the tunnel span. Moreover, the influence range of the settlement tank obtained by the back analysis of random medium theory is closer to the actual measurement range. For example, in the literature [9], the measured settlement tank width is about 19.5 m, the random medium theoretical back analysis result is about 17.1 m, and the Peck back analysis result is about 14 m; the literature [10], the measured settlement tank width is about 17 m, and the random medium theoretical back analysis result is about 16.4 m, the Peck back analysis result is about 11.2 m; literature [11], the measured settlement tank width is about 14 m. The random medium theory back analysis result is about 14.2 m, and the Peck back analysis result is about 12.2 m. This fully verified the conclusion of the previous section. In addition, the significance of the calculation results in Table 3.3 is to perfect the current domestic research results. Chinese scholars have obtained the ground movement parameters tan(β) and ΔA caused by the excavation of various tunnels around the world and in Guangzhou, Liuzhou, Hong Kong, Taiwan and the northwestern region of my country using the back analysis method of random medium theory. This chapter analyzes the relevant parameters in other regions of my country through this method, and provides a basis for further improvement of related research.

3.5 Conclusion Existing surface deformation analysis methods often require experience to determine relevant surface movement parameters when performing surface deformation predictions. The parameters of different formation conditions will be quite different. This chapter uses two different methods to conduct an in-depth analysis of specific geological conditions based on measured data. For the typical ‘soft top and hard bottom’ characteristics of the stratum in this area, the characteristics of surface settlement caused by the construction of a large-span shallow buried subway station are as follows: (1) The width of the settlement i /R = (H/2R)n is the closest to the i-value fitting result of the unique formation conditions in the area trough uses the formula and the calculation result when n = 1.0;

Document Engineering and observation section

The middle hole of the 14th section of the city railway (K39 + 313)

Metro line 5 Dongdan station

Retreat channel of Gaobeidian Sewage Treatment Plant

Liangshui River South BankSewage trunk(0 + 782)

As above

Subway Fuxingmen Turnback line

Zhang Yun 2004 [3]

Xiao Zhitao 2004 [4]

Liang Jianning 1993 [5]

Guo Yuhai, 2004 [6]

Zhou Xiupu 2004 [8]

Wang Mengru, 1989 [9]

City

Bei jing

14.2

7.4

5.0

12.2

9.0

8.0 × 6.4

3.33

Filling, fine sand, silt sand

Underground House muck, dig bury clay, silt

Shield

Silt fine sand, gravel

pebble

Silt

Underground Silt contain dig shallow water bury

5.3 × 4.3

Full section

29.7

27 12

525 ring

6

27

577 ring

Full section

Middle arch

45

Full section Silt, powdery Left hole 24.5 clay, silty, Right 19.5 medium-coarse hole sand, pebbles

35

Lower hole

Underground Silt, powdery dig clay, silty, medium-coarse sand, pebbles

8

Upper hole

15.80

10.1

18.7

4.60

20.3

1.393

0.717

0.930

0.917

0.363

0.915 1.052

14.6

0.587

0.686

0.361

12.2

32.80

21.3

10.7

4.85

–

–

3.16

4.47

5.77

6.45

5.59

5.27

5.00

(continued)

5.68

4.79

3.84

3.89

6.60

5.799

6.49

6.83

5.95

8.17

Working Max ΔA (mm) tan(β) i R (m) i [2] condition settlement (m) (mm)

5.8 × 6.3

Excavation surface geological conditions Silty clay

Overlying soil

3.5 × 7 Underground Mix soil dig

Burydepth Section Dig method (m) size (m)

Table 3.3 Back analysis parameters of ground deformation caused by tunnel construction in some regions of my country

3.5 Conclusion 43

Chongqing Gong Shan long, 2005 [13]

Ji yaping, 2004 [10]

A bid section of main city drainage project

2.6

Metro Phase I 18.0 Station-Jintian station interval

As above

2.2

6

6.8 × 13.2

Overlying soil

Shallow top tube

Shield

Miscellaneous low-strength mudstone

Plain fill, sandy soil

Underground Powdery, fully dig weathered granite gneiss and tuff

Burydepth Section Dig method (m) size (m)

3C bid section 20.0 of the first phase of the subway (SK1 + 654.3)

Document Engineering and observation section

Shen Zhen Wan Jianglin, 2004 [12]

City

Table 3.3 (continued)

Miscellaneous low-strength mudstone

sandy soil

Powdery, fully weathered granite gneiss and tuff

Excavation surface geological conditions

24.98 27.35

3 step 4 step

Full section

Full section

47

31

30

16.87

2 step

Full section

9.0

1 step

25.30

53.10

27.50

21.20

24.40

20.10

13.90

0.799

0.562

0.557

0.667

0.624

0.636

0.570

1.74

14.01

16.14

13.71

13.34

12.24

12.52

–

11.70

14.14

11.79

11.95

12.31

13.41

Working Max ΔA (mm) tan(β) i R (m) i [2] condition settlement (m) (mm)

44 3 Analysis of Ground Settlement Caused by Subway …

References

45

(2) The direct integration and adaptive genetic algorithm used in the inverse analysis and optimization calculations in this chapter can obtain the ground movement parameters more accurately; (3) The influence angle of surface settlement caused by the excavation of a typical subway station in this area is tan(β) = 1.45, which is about 55°; (4) The comparative analysis of the two methods of Peck and random medium theory confirms that the width of the settlement trough fitted by the Peck method is smaller than the actual width of the settlement trough, especially when the excavation span is large. Combined with the research conclusions in this chapter, the maximum surface settlement value and the range of settlement troughs caused by the excavation of subway stations under such geological conditions can be preliminarily predicted, which provides a basis for the prediction of construction environmental impact.

References 1. Peck RB (1969) Deep excavations and tunneling in soft ground, state of the art report. In: Proceedings of 7th international conference on soil mechanics and foundation engineering, Mexico City, 225–290 2. Liu B-c, Zhang J-s (1995) Surface subsidence induced by near-surface excavation with random medium method. J Geomech Geotech Eng 3. Loganathan N, Poulos HG (1998) Analytical prediction for tunneling -induced ground movements in clays. J Geotech Geoenviron Eng ASCE 124(9):846–856 4. Atkinson JH, Potts DM (1977) Subsidence above shallow tunnels in soft ground. J Geotech Eng Divis ASCE 103(GT4):307–325 5. Tan Y, Liu C, Zhao T (2008) Preliminary study on nonlinear dynamics of rock. Coal Industry Press, Beijing 6. Meng D, Zang X, Yu G et al (2012) Chin J Rock Mech Eng 31(6):1–6 7. Junsheng Y (2002) Surface movement and deformation caused by urban tunnel construction. China Railway Publishing House, Beijing 8. Korea warmth. Research on practical method for prediction of ground displacement and building deformation caused by tunnel construction. Xi‘an University of Technology, Xi ‘an 9. Yun D (2004) Tunnel Constr 24(2):40–42 10. Jianning L (1993) Monitoring and analysis of settlement in shallow tunnel excavation. Municipal Technol Z1:43–48 11. Xiupu Z (2004) Deformation analysis of shield tunnel construction in anhydrous gravel stratum. Municipal Technol (Supplement) 22:385–388 12. Zhitao X, Zhanbo H (2004) Tunnel Constr 24(4):61–64 13. Yuhai G (2004) Research on settlement control of shield tunnel crossing railway. Municipal Technol (Supplement) 22:247–251

Chapter 4

Analysis of Deformation and Stress of Buildings Under Tunnel

It can be seen from the existing research results on building damage caused by the tunnel underpassing the building that the additional stress shown by the building under the influence of ground settlement is extremely complicated. Evaluation of the safety of buildings can not meet the needs of engineering applications [1–6]. The finite element method is a powerful tool to analyze the impact of tunnel construction on the overall structure of the building [7–10]. this chapter takes a subway tunnel underneath a building in Qingdao as an example, uses the surface settlement data monitored during the construction process, and the random medium theory method and the Peck method to back-analyze the surface movement parameters; the accurately predicted surface settlement results are applied to the study Object building. Physically, a three-dimensional analysis model is established through finite element to analyze the general law of building settlement deformation and additional stress generated.

4.1 Project Overview This section selects a reinforced concrete frame-shear wall structure building under a certain section of Qingdao Metro Line 3 tunnel—the public resource trading hall in Shinan District of Qingdao City as the object (Fig. 4.1), and analyzes its tunnel construction For the settlement and deformation laws under the influence, the relative position relationship between the building and the double-track tunnel is shown in Fig. 4.2. The basic conditions of buildings and tunnels related to the research in this article are shown in Table 4.1. The geological conditions of the section of the tunnel under the building are shown in Fig. 4.3

© China Architecture Publishing & Media Co., Ltd. 2022 D. Meng et al., Prediction and Control of Interaction Between Ground Building and Tunnel Construction Process, https://doi.org/10.1007/978-981-19-3474-2_4

47

48

4 Analysis of Deformation and Stress of Buildings Under Tunnel

Fig. 4.1 Research object-public resource trading floor

Fig. 4.2 The relative position relationship between the building and the tunnel underneath

Table 4.1 Basic conditions of buildings and tunnels Tunnel Building House structure section storeys (m)

5.86 × 6.4

15

Foundation method and depth

Buried depth of tunnel vault (m)

Framework Raft 23.5 foundation and anti-floating anchor rod/13 m

Distance between vault and foundation (m)

Blasting vibration control value (cm/s)

Building settlement control value (cm)

10.5

2

2

4.2 Stratum Subsidence Law

49

Fig. 4.3 Geological profile of the section underneath the building

4.2 Stratum Subsidence Law 4.2.1 Peck Method Inverse Analysis of Ground Movement Parameters The data of the selected 6 sections (numbered 20, 21, 22, 23, 25 according to the actual monitoring section on the spot) are fitted, and the fitting parameter is the distance i of the reversal point. Based on the tunnel excavation size, the parameter Vl is obtained through theoretical calculation; the settlement curve is drawn based on the above two parameters, and the fitting result of section 20 is shown in Fig. 4.4. It can be seen from Fig. 4.4 that the use of Gaussian distribution curve for fitting can better reflect the lateral ground settlement caused by tunnel excavation. This method is used to fit the settlement data of the other five sections of the tunnel, as shown in 1

ln(S/S

max

)

0 -1 -2 -3 -4 0

200

400

x2

600

800

1000

Fig. 4.4 Fitting results of surface settlement at section 20 (i = 12.66 m Vl = 0.0198, burial depth 21.75 m)

50

4 Analysis of Deformation and Stress of Buildings Under Tunnel

Fig. 4.5. The width of settlement trough and formation loss rate of each section are shown in Table 4.2.

4.2.2 Random Medium Theory Back Analysis of Ground Movement Parameters The random medium theory can be used to predict the surface settlement caused by tunnel excavation. The two parameters, the tangent value tanβ (or β) of the influence angle of the ground conditions at the excavation position and the uniform shrinkage value ΔA of the tunnel section, depend on the excavation position. Factors such as specific ground conditions, construction methods and construction conditions used are the result of a comprehensive influence of multiple influencing factors. Table 4.3 shows the surface movement parameter results of multiple monitoring sections in similar formations obtained according to the analysis method in Sect. 3.2.2. Figure 4.6 shows the comparison between the predicted results of the inverse analysis parameters of the 6 sections and the measured results.

4.3 Analysis of Vertical Displacement of Frame-Shear Wall Structure 4.3.1 Finite Element Model The values of the model parameters are derived from the design data of the building and the on-site inspection results. The concrete structure has a total height of 55.4 m, a total of 15 floors, and a storey height of 3.6 m (the first storey is designed as a store with a storey height of 5.0 m). The floor plan is shown in Fig. 4.7. See Table 4.4 for section size of components, concrete strength grade and reinforcement ratio. The finite element model of the structure is shown in Fig. 4.8. The shear walls and floor slabs in the model are all cast-in-place reinforced concrete. The parameters of the concrete material are Poisson’s ratio δ1 = 0.2, density ρ = 2500kg/m3 , and the other parameters are the same as the MISO-type multi-linear strengthening model.

4.3.2 Settlement Conditions Imposed by the Model For comparative research, we select two working conditions for analysis. One is the impact on the building when the ground subsidence is small at the initial stage of the tunnel excavation; the other is the impact on the building when the ground

4.3 Analysis of Vertical Displacement of Frame-Shear Wall Structure 0

ln(S/S

max

)

-0.5 -1

-1.5 -2 0

100

200

300

400

x2

500

600

(a) Surface settlement fitting results of section 21 ( i = 12.03m

Vl = 0.0161

burial depth 16.6m)

Vl = 0.0179

burial depth 21.1m)

Vl = 0.0189

burial depth 22.0m)

Vl = 0.0215

burial depth 18.6m)

Vl = 0.0185

burial depth 20.6m)

1

)

0

ln(S/S

max

-1 -2 -3 -4 0

200

400

x2

600

800

1000

(b) Surface settlement fitting results of section 22 ( i = 12.59m 1

ln(S/S

max

)

0 -1 -2 -3 -4 0

200

400

x2

600

800

1000

(c) Surface settlement fitting results of section 23( i = 12.66m 0

ln(S/S

max

)

-1 -2 -3 -4 0

500

x2

1000

1500

(d) Surface settlement fitting results of section 24 ( i = 14.35m

-1

ln(S/S

max

)

0

-2

-3 0

100

200

300 x2

400

500

600

(e) Surface settlement fitting results of section 25 ( i = 13.75m

Fig. 4.5 Fitting analysis of surface settlement at other sections

51

52

4 Analysis of Deformation and Stress of Buildings Under Tunnel

Table 4.2 Statistics of surface subsidence law of each section Section number

Burial depth (m)

Settling trough width (m)

Settling trough width parameter

Formation loss rate

20

21.8

12.66

0.71

0.0198

21

16.6

12.03

0.59

0.0161

22

21.1

12.59

0.59

0.0179

23

22.0

12.66

0.60

0.0189

24

18.6

14.35

0.56

0.0215

25

20.6

13.75

0.63

0.0185

0.613

0.01928

Average

Table 4.3 Inverse analysis parameters of surface settlement Section tan (β) ΔR (mm)

1 1.110 11.34

2 0.813 18.13

3 0.712 19.75

4 0.724 19.67

5 0.719 15.89

6 0.634 13.40

subsidence at the place becomes stable. Impact. The specific application conditions are as follows: Working condition 1: Width parameter of surface settlement trough K = 0.613, formation loss rate. Vl = 0.0035. Working condition 2: Width parameter of surface settlement trough K = 0.613, formation loss rate Vl = 0.01928. Working condition 1: Width parameter of surface settlement trough K = 0.613, formation loss rate. Vl = 0.0035. Working condition 2: Width parameter of surface settlement trough K = 0.613, formation loss rate Vl = 0.01928.

4.3.3 Displacement and Stress Analysis of Structures Under Different Working Conditions (1)

Surface settlement conditions 1

In order to analyze the influence of surface settlement on the vertical displacement of buildings, firstly, the vertical displacement caused by gravity on the building is analyzed. According to the aforementioned load application method, the vertical displacement of the building under the action of gravity is shown in Fig. 4.9. It can be seen from the vertical displacement cloud diagram that the maximum displacement value of the building under its own gravity appears in the middle of the building plane, with a size of 7.3 mm.

4.3 Analysis of Vertical Displacement of Frame-Shear Wall Structure

Section 20

53

Section 21

Section 22

Section 23

Section 24

Section 25

Fig. 4.6 Prediction curve and measured value of tunnel section back analysis result

Apply the settlement deformation of working condition 1 to the bottom of the building, and get the displacement cloud diagram of the building as shown in Fig. 4.10. At the same time, the building stress distribution cloud map is extracted from the model analysis results, as shown in Figs. 4.11 and 4.12. Figure 4.12 shows the stress distribution under the sole action of gravity load, and Fig. 4.12 shows the stress distribution under the simultaneous action of gravity load and settlement load. It can be seen from the figure that the stress in the building is large at the bottom and small at the top. As the load increases, the equivalent stress also increases. Figure 4.13 extracts the vertical displacement under the gravity load, the vertical settlement load, and the combined action of the two loads. In the direction of the long axis of the building, due to the large size range and the influence of the shear wall, the vertical displacement of the concrete beam on the top of the first floor is

54

4 Analysis of Deformation and Stress of Buildings Under Tunnel

Fig. 4.7 Building plan and section cutting position

Table 4.4 Component attribute Component

Section measurement Concrete strength grade Reinforcement ratio (%)

Pillar1 (1–7 floor)

700 mm × 700 mm

C40

0.80

Pillar2 (7–15 floor) 600 mm × 600 mm

C35

0.78

Frame beam 1

300 mm × 650 mm

C35

0.79

Frame beam 2

250 mm × 400 mm

C35

0.79

Connecting beams

250 mm × 400 mm

C35

0.81

Shear wall

h = 250 mm

C35

0.36

not a straight line under the action of gravity. At the same time, the overall vertical displacement is caused by the ground settlement. The longitudinal deformation also conforms to the distribution shape of the settlement tank. Figure 4.14 is the equivalent stress curve of the top layer of the two sections. It can be seen from the figure that the stress in the building is large at the bottom and small at the top. As the load increases, the equivalent stress also increases. In addition, stress concentration occurs at the joints of the frame and the shear wall. According to the existing research results, the equivalent stress of the concrete structure reaches a certain level, which will cause the structural members to crack (Fig. 4.14). (2)

Surface settlement conditions 2

The settlement load of condition 2 is applied to the building, and the vertical displacement cloud diagram of the building under the combined action of gravity and settlement load is shown in Fig. 4.15, and the displacement cloud diagram under the

4.3 Analysis of Vertical Displacement of Frame-Shear Wall Structure

Fig. 4.8 Three-dimensional finite element model of the structure

(a) front

(b) back

(c) profile 1

(d) profile 2

Fig. 4.9 Vertical displacement under gravity

55

56

4 Analysis of Deformation and Stress of Buildings Under Tunnel

(a) front

(c) profile 1

(b) back

(d) profile 2

Fig. 4.10 Vertical displacement due to settlement

sole action of the settlement load is shown in Fig. 4.16. The equivalent stress cloud diagram under the action of and settlement load is shown in Fig. 4.17. It can be seen from the results that the distribution law of vertical displacement and equivalent stress is basically the same as that of working condition 1, and the values have changed. The vertical displacement curves of the top layer of the two sections are shown in Fig. 4.18. From the vertical displacement distribution curve of the longitudinal section in the figure, it can be seen that the deformation law of the building under the two working conditions is basically the same. The equivalent stress curve at the top of the first layer of the two sections is shown in Fig. 4.19. Figures 4.20, 4.21, 4.22 and 4.23 show the displacement and the equivalent stress curvature effect force variation range of the two sections of the building under different working conditions. According to these analysis results, it is possible to clearly understand the deformation and force changes of the building under different working conditions, which provides a theoretical basis for the protection of the building.

4.4 Conclusion

57

(a) front

(c) profile 1

(b) back

(d) profile 2

Fig. 4.11 Equivalent stress diagram under gravity

4.4 Conclusion In this chapter, by predicting the ground settlement below the building, using theoretical methods, based on the measured ground settlement data, the ground surface deformation parameters of specific ground conditions are back-analyzed, and the finite element model of the reinforced concrete frame-shear wall structure of the research object is established. The vertical deformation laws of buildings under the action of ground settlement loads, and the following conclusions are obtained: (1)

(2)

The deformation parameters of the ground where the target building is located are: the width parameter of the surface settlement groove K = 0.613, the formation loss rate Vl = 0.01928, the main influence angle tangent value is tan β = 0.785, and the average section shrinkage ΔR = 16.36 mm; As the degree of surface deformation increases, the vertical displacement of the structure increases, and the law of vertical displacement of the structure is affected by the law of surface deformation;

58

4 Analysis of Deformation and Stress of Buildings Under Tunnel

(a) front

(c) profile 1

(b) back

(d)profile 2

Fig. 4.12 Equivalent stress diagram under gravity and settlement (conditions 1)

(a) profile 1 Fig. 4.13 Settlement curve at the top of the first layer of section 1

(b) profile 2

4.4 Conclusion

59

(a) profile 1

(b) profile 2

Fig. 4.14 Equivalent stress curve at the top of the first layer of section 1

(a) front

(b) back

(c) profile 1

(d) profile 2

Fig. 4.15 Vertical displacement under gravity and settlement

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4 Analysis of Deformation and Stress of Buildings Under Tunnel

(a) front

(c) profile1

(b) back

(d) profile 2

Fig. 4.16 Vertical displacement under settlement

(3)

The research object building in this chapter is above the surface settlement curve caused by tunnel excavation. The middle of the building is affected by surface settlement in a large area. The deformation of structural members will increase the effective stress of reinforced concrete materials and cause additional stress. Cause damage to the structure.

4.4 Conclusion

61

(a) front

(c) profile1

(b) back

(d) profile 2

Fig. 4.17 Equivalent stress diagram under gravity and settlement (conditions 2)

(a) profile 1

(b) profile 2

Fig. 4.18 Settlement curve of the top layer of the first floor of the working condition 2 section

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4 Analysis of Deformation and Stress of Buildings Under Tunnel

(a) profile 1

(b) profile 2

Fig. 4.19 The equivalent stress curve at the top of the first layer of the section of working condition 2

Fig. 4.20 Settlement curve of the top layer of section 1 under different working condition

Fig. 4.21 The equivalent stress curve at the top of section 1 under different working conditions

References

63

Fig. 4.22 Settlement curve of the top layer of section under different working conditions

Fig. 4.23 The equivalent stress curve at the top section 1 under different working conditions

References 1. Wan J (2004) Analysis of Surface and supporting Structure Deformation caused by Construction of shallow single-hole double-layer overlapping tunnel. Modern Tunnel Technol 24–29 2. Ji Y (2004) Research on ground displacement and earth pressure of shield tunnel considering construction process [D]. Hohai University, Nanjing 3. Gong S, Yang Z, Chen S (2005) Analysis of surface settlement caused by ultra-shallow curve pipe jacking using stochastic medium theory. J Chongqing Jiaotong Univ 24(6):95–98 4. Meng D, Pang F (2017) Co-evolution analysis of defects under the influence of deformation of elevated residential foundation in Kashgar, Xinjiang. J Shanghai Univ Nat Sci 23(5):772–779 5. Luo R, Jiang Y, Wan M et al (2009) Surface deformation monitoring and finite element simulation in jacking construction of pipe curtain box culvert. J Shanghai Univ Nat Sci 15(5):534–540 6. Li L, Dong Y (2017) A safety assessment method for adjacent buildings under underground excavation and unloading. Civ Eng Manag J 34(6):23–28 7. Zhao L, Zhang J, Zhou J et al (2017) Railway Standard Design 61(12):96–100 8. Li C, Miao L, Chen J (2017) Studies on ground surface and building settlement rule by shield passing through building. J Shandong Univ Technol Nat Sci 31(1):12–16 (in Chinese) 9. Li F, Chen G (2017) Study on the Influence of Metro Tunnel Shield Construction on the Pile Box Building. Railway Standard Design 62(2):1–6 (in Chinese) 10. Sun X, Ji C, Liu T (2017) Research on influence of shallow tunneling method on surface building. Construction Technology 48(11):1214–1216 (in Chinese)

Chapter 5

Quantitative Prediction Method of Building Damage

When urban subway tunnels pass through buildings, the control standards of engineering settlement and blasting vibration have always been basic problems that are difficult to solve. This chapter combines the engineering practice of the Qingdao subway tunnel underpassing the building. Firstly, based on the measured data of surface settlement, the stochastic medium theory method is used to back-analyze the surface movement parameters, including the influence range of the settlement trough and the section shrinkage rate. Prediction of settlement was made when crossing the building. Secondly, based on 8 concrete failure criteria such as Ottosen and GuoWang, a yield proximity model suitable for concrete materials is derived. Through the finite element calculation, the stress distribution of the building structure under the influence of surface settlement and blasting vibration is obtained, and the damage distribution range and evolution process of the building structure are obtained by combining the yield proximity function of Ottosen and the Guo-Wang failure criterion. As a result, the quantitative assessment and control of the cracking damage of the building structure under the influence of different settlements and blasting vibration speeds are realized. The research results show that in the evolution of building structure cracking damage, the impact of ground settlement is much greater than the impact of blasting vibration; the use of the calculation method in this chapter to predict the distribution of building structure cracking damage and the control standards given will affect the subway tunnel crossing the building. On-site construction has important reference value.

5.1 Project Overview and Settlement Prediction 5.1.1 Project Overview The length of the interval between Wannianquan Road Station and Licun Station is 1085.65 m in the civil engineering 11 bidding of the first phase of Qingdao Metro © China Architecture Publishing & Media Co., Ltd. 2022 D. Meng et al., Prediction and Control of Interaction Between Ground Building and Tunnel Construction Process, https://doi.org/10.1007/978-981-19-3474-2_5

65

66

5 Quantitative Prediction Method of Building Damage

(Line 3). The interval tunnels are constructed by drilling and blasting. The stepping method is used to excavate the section that passes through the sand, and the cross section is all horseshoe-shaped. The section departs from Wannianquan Road Station, passing through District J of Binhe Road Commercial Street, houses along the street on the north side of Li Village, Wanlong Commercial Building, F1 Floor of Real Estate Office in Laoshan District, Staff Dormitory of Li Village Reformation Team, China Telecom Jingkou Road Business Office, After 7 buildings including Bank of China Licun Sub-branch, arrived at Licun Station. The research object of this article is one of the 7 buildings under the section-Bandung Commercial Building. The relative position relationship between this building and the section tunnel is shown in Fig. 5.1. The length of the interval tunnel passing through the commercial buildings of Bandung: left K19 + 533.5 ~ left K19 + 590.00, the section size of the tunnel is 6.35 × 5.9 m, and the surrounding rock grade is VI. Before the excavation of the tunnel through the Bandung commercial building, the water-rich sand layer was pre-grouted and reinforced with cement–water glass double grout. During excavation, the leading small pipe is Φ42, the length is 3 m, the ring longitudinal spacing is 300 × 1000 mm, the longitudinal spacing of the section steel arch is 500 mm, the 250 mm thick shotcrete, the single-layer steel mesh is 8@150 × 150 mm, and each steel arch is 8 Φ42, L = 3.5 m lock foot anchor pipe, the lower half section of the first sprayed concrete 100 mm.

Fig. 5.1 The relative position relationship between the building and the tunnel

5.1 Project Overview and Settlement Prediction

67

5.1.2 Settlement Prediction The purpose of this section is to back-analyze the surface movement parameters through the measured data of the ground settlement before passing through the building through the tunnel, so as to predict the ground settlement under the building. The inverse analysis method of ground movement parameters is shown in Sect. 5.3.2 of this article. The difference here is that the tunnel is a two-lane section tunnel. Two-line circular section subway tunnel, the two tunnels are on the same horizontal plane, the tunnel excavation depth is H, the initial radius of the excavation is As , and the center distance between the two tunnels is L (L > As ), and the coordinate system shown in Fig. 5.2 is established. After the completion of the tunnel construction, the radius shrinkage values of tunnel I and tunnel II are both ΔAs . Then, the total ground subsidence S(x) is the ground subsidence SI (x) caused by the excavation of the tunnel I (see formula (3.31) for the expression) and the ground subsidence S∥ (x) caused by the excavation of the tunnel (II) Linear superposition. S(x) = SI (x) + S∥ (x) where, (b1 (d1

(f1 (h 1 sI (x, ξ, η)dξ dη −

SI (x) = a1 c1

⌈

sI (x, ξ, η)dξ dη, e1 g1

( )2 ⏋ L π tan2 β tan β x+ − ξ exp − sI (x, ξ, η) = , η η2 2

Fig. 5.2 Schematic diagram of excavation of a circular double-track tunnel

(5.1)

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5 Quantitative Prediction Method of Building Damage

(b2 (d2

(f2 (h 2 s∥ (x, ξ, η)dξ dη −

S∥ (x) = a2 c2

s∥ (x, ξ, η)dξ dη, e2 g2

( )2 ⏋ tan β L π tan2 β s∥ (x, ξ, η) = . x − −ξ exp − η η2 2 ⌈

where, a1 = a2 = H − A s , b1 = b2 = H + As , / L c1 = − A2s − (H − η)2 ∓ , c2 2 / L d1 = A2s − (H − η)2 ∓ , d2 2 e1 = e2 = H − (As − ΔAs ), f 1 = f 2 = H + (As − ΔAs ), / L g1 = − (As − ΔAs )2 − (H − η)2 ∓ , g2 2 / L h1 = (As − ΔAs )2 − (H − η)2 ∓ . h2 2 Aiming at this integration interval, this section selects five sections to conduct the back analysis of ground movement parameters, and the back analysis results of each section are shown in Table 5.1. Section 1 uses the back analysis parameters to predict the surface settlement of the section, the measured value of the surface settlement and the calculated value of each measurement point in the back analysis process, as shown in Fig. 5.3. The settlement prediction curves and measured values of the remaining sections are shown in Fig. 5.4. In order to further analyze the structural cracking damage and evolution process when the tunnel passes through the building, the average value of the back analysis parameters of the above 5 sections (Table 5.1) is used to predict the ground settlement results under the building. The result is shown in Fig. 5.5 (H = 13.4m, L = 17.0m).

5.1 Project Overview and Settlement Prediction

69

Table 5.1 Back-analysis parameters of surface settlement Section

H (m)

L(m)

tan(β)

ΔAs (mm)

1

19.5

14.5

0.7322

20.2

2

19.8

14.4

0.7657

21.4

3

20.6

15.4

0.8120

18.3

4

23.8

16.3

1.0460

21.8

5

22.1

16.2

Average

0.9262

17.4

0.8564

19.8

Fig. 5.3 Prediction curve and measured value of back analysis results of each section of the tunnel

Fig. 5.4 Surface subsidence prediction curves of different sections of tunnel

70

5 Quantitative Prediction Method of Building Damage

Fig. 5.5 Curves for prediction of surface settlement at different excavation stages of the tunnel section

5.2 Building Structure Damage Prediction Method 5.2.1 Yield Proximity Function In reference [1], in order to study the stability of surrounding rock, the calculation function of yield proximity was derived based on classical strength theories such as Mohr–Coulomb criterion. The specific method is to assume that the problem is an ideal elastoplastic problem, and assume that the strength criterion of the rock is Mohr–Coulomb criterion or other yield criterion. According to the relationship between the non-yield stress point and the yield surface in the principal stress space, it is defined within the framework of classical plastic theory. The yield proximity index is established, and the yield proximity function corresponding to different types of yield criteria is established. The yield proximity function of the Mohr–Coulomb criterion is: /√ /√ √ 3I1 sin ϕ + (cos θσ − 1 3 sin θσ sin ϕ) J2 F(σπ , τπ , θσ ) = [1 /√ (5.2) 3I1 sin ϕ − c cos ϕ) − c cos ϕ]/(1 /√ √ 3 are shear stress and normal stress on the π where, τπ = 2J2 and σπ = I1 plane, respectively;J2 is the second deviator stress invariant, I1 is the first principal stress invariant, c is the shear strength, ϕ is the angle of internal friction, θσ is the stress rode’s angle. However, the classical strength theories are all proposed for a specific material, and its failure envelope surface is quite different from the failure envelope surface of reinforced concrete materials in civil engineering, especially for the force analysis of

5.2 Building Structure Damage Prediction Method

71

the entire structure. In order to solve the problem of cracking damage of the concrete structure of the research object of this section, the failure criterion of concrete material is introduced here to establish the corresponding yield proximity model. The commonly used Ottosen failure criterion is expressed as [2]: √ J2 I1 J2 +b −1=0 a 2 +λ fc fc fc

(5.3)

where, f c is the uniaxial compressive strength of concrete materials. According to √

(σ1 − σ2 )2 + (σ2 − σ3 )2 + (σ3 − σ1 )2 τ0 f c = = 3 / / = (σ1 + σ2 + σ3 ) 3 = I1 3

/

2J2 and σ0 f c 3 (5.4)

The formula (5.3) can be changed to 1 σ0 − + 3b

/

1λ a τ0 + τ02 = 0 6b 2b

(5.5)

√ Let H = 3 f c , according to the definition of the yield proximity function, the yield proximity function of the Ottosen failure criterion can be obtained as

f (σπ , τπ ) =

/

π B 2 − 4C(H H·A−σπ ) − 2C·τ H / −B − B 2 − 4C(H H·A−σπ )

−B −

(5.6)

/ / / / / where, A = 1 3b, B = − 1 6λ b, C = −a 2b. According to this method, this section derives the yield proximity functions of other common concrete failure criteria, as shown in Table 5.2. Yield proximity can be broadly described as the ratio of the current state of a point to the parameter of the relatively safest state f ∈ [0, 1],. At the same time, yield proximity is also a definition of cracking safety, which has characteristics of distribution and evolution, and its mechanical meaning is clear. Therefore, it would be appropriate to use yield proximity to define the cracking safety of the structure. Therefore, this section defines the structural cracking damage safety as: ⎧ ⎨ [0.0, 0.1] f (σπ , τπ ) = [0.1, 0.2] ⎩ [0.2, 1.0]

Cracking, damage, and destruction Close to cracking damage Safety structure

(5.7)

3

Willam-Warnke

b b b τ0c = √ 2 σ02 + √ 1 σ0 + √ 0 0.6 0.6 0.6

θ = 0◦ , a a a τ0t = √ 2 σ02 + √ 1 σ0 + √ 0 θ = 60◦ , 0.6 0.6 0.6

A = a, B = −b, C = c /√ 0.6, θ = 0 ◦ , A = a2 /√ 0.6, B = a1 /√ 0.6 C = a0 /√ 0.6, θ = 60◦ , A = b2 /√ 0.6, B = b1 /√ 0.6 C = b0 2 H A−Bσπ + C H σπ −τπ C H A−Bσπ + H σπ2

τ0 = a − bσ0 + cσ02

Bresler-Pister

1 − c σ1 , A = 3d 3d f c / a B = − 16 db ,C = − 2d

A = c0 , B = −c1 P, C = −c2 f c

/ π ) − 2C·τπ −B− B 2 − 4C(H ·A−σ H H / 4C(H ·A−σ π) −B− B 2 − H

Yield proximity function \ ( σ ( σ )d )d b− π/ H b− π/ H aH · − τ aH · π σ σ π π c− / H c− / H / ( / ) / )b ( b θ = 0◦ , a H · c − σπ H − τπ a H · c − σπ H / )e / ( / )e ( θ = 60◦ ,d H · c − σπ H − τπ d H · c − σπ H /√ / A=c 3, B = −b φ, √ / C = − 3a φ 2

σ0 = −c2 f c · τ02 − c1 P · τ0 + c0

/ 1b a τ0 σ0 = − τ02 − 2d 6d ) ( c σ1 1 − + 3d 3d f c

φ

√ σ0 = − 3 a2 τ02 − φb τ0 + √1 c

θ = 0◦ , τ0t = a(c − σ0 )b θ = 60◦ , τ0t = d(c − σ0 )e

( )d / τ0 = a b − σ0 c − σ 0

Formula

Podgorski

Hsieh-Ting-Chen

Reimann

Kotsovos

Guo-wang

Damage rule

Table 5.2 Yield proximity function of concrete failure criterion

72 5 Quantitative Prediction Method of Building Damage

5.2 Building Structure Damage Prediction Method

73

5.2.2 Analysis of Damage Results of Concrete Building Structures In order to obtain the corresponding principal stress and deviator stress invariants in the yield proximity damage model based on the concrete failure criterion, a finite element model is established by selecting a frame of the building in Fig. 5.1, as shown in Fig. 5.6. In the process of establishing the finite element model, the relevant parameters are determined according to the on-site inspection results: ➀ The frame structure has a height of 4.2 m, with a total of 9 floors; ➁ The size of the component: column section 600 mm × 600 mm, beam section 200 mm × 400 mm; ➂ Concrete material: The beams and columns are all made of C35 concrete, Poisson’s ratio μ1 = 0.2, density ρ = 2700 kg/m3; ➃Reinforcement amount of components: The type of steel bars used in the components are all HRB335, symmetrical reinforcement, and the column reinforcement rate is 1.1%. The reinforcement ratio is 0.4% (Fig. 5.7). In the calculation of cracking damage of building structure, we select two failure criteria to calculate separately. In the Ottosen guidelines, (

┌ −1 / ⏋ λ = k┌ 1 cos cos (k2 cos 3θ ) 3 / ⏋ θ ≤ 30◦ / θ ≤ 30◦ λ = k1 cos π 3 − cos−1 (−k2 cos 3θ ) 3

(5.8)

The four parameters in this criterion are taken as: a = 1.2759, b = 3.1962, k1 = 11.7365, k2 = 0.9801. As Guo-Wang rule c = ct (cos 1.5θ )1.5 + cc (sin 1.5θ )2

(5.9)

and the five parameters in this criterion are a = 6.9638, b = 0.09, d = 0.9297, ct = 12.2445, cc = 7.3319 respectively. It can be seen from Figs. 5.8 that the prediction results of the Ottosen criterion show that 5 places of the first-floor frame beams enter a cracked or close to cracking state, and the prediction of the Guo-Wang criterion shows that 11 places are cracked or close to a cracked state. The stress distribution and cracking damage of the top beam are shown in Fig. 5.9. The prediction result of the Ottosen criterion shows that 7 places of the top frame beam are cracked or close to cracking, and the prediction of the Guo-Wang criterion shows that 10 places are cracked or close to cracking. After the excavation of the double-track tunnel is completed, the surface settlement curve is the saddle-shaped final settlement curve shown in Fig. 5.5. Apply this settlement value as a boundary condition to the model. The first principal stress cloud diagram is shown in Fig. 5.10, and the stress distribution and cracking damage of the frame beam on the first floor are shown in Fig. 5.11. It can be seen from Fig. 5.11 that the stress distribution of the building structure has changed compared to the left-line excavation after the double-line excavation is completed, the maximum stress has

74

5 Quantitative Prediction Method of Building Damage

Fig. 5.6 Frame structure finite element model

become smaller, the frame stress distribution is more uniform, and the damage has been further aggravated.

5.3 The Impact of Blasting Vibration on Concrete Structure Damage Prediction and Control Standards 5.3.1 Settlement Control Standard From the analysis of the damage results of the building structure in the previous section, it can be seen that when the concrete structure is affected by the tunnel excavation predicted surface settlement, there will be several areas of cracking damage.

5.3 The Impact of Blasting Vibration on Concrete Structure …

75

Fig. 5.7 The first principal stress cloud diagram of the structure after the left line excavation is completed

Fig. 5.8 Excavation of the left line completes a first-story frame beam: a stress distribution curve; b yield proximity distribution curve

76

5 Quantitative Prediction Method of Building Damage

Fig. 5.9 Excavation of the left line completes the top-level frame beam: a stress distribution curve; b yield proximity distribution curve

Fig. 5.10 The first principal stress cloud diagram of the final settlement structure

Therefore, this section adjusts the formation deformation parameters on the basis of the previous section, changes the range and size of the surface settlement, and calculates the structural stress and damage under the influence of various surface settlements. Among them, when the maximum surface settlement of the ground is controlled to 18 mm, the first principal stress cloud diagram of the building structure is shown in Fig. 5.12, and the stress distribution of the first layer of beams, and the damage and destruction of the first layer and the top layer are shown in Fig. 5.13. It can be seen from Fig. 5.13 that under the influence of the ground settlement, the minimum yield proximity of the concrete beam is about 0.23, and cracking damage will not occur. Combining the structural damage in Fig. 5.8 and Fig. 5.9, and the surface settlement in Fig. 5.5, this section believes that it is more appropriate to control the maximum surface settlement at 18 mm. Within this range, the building will not suffer cracking damage.

5.3 The Impact of Blasting Vibration on Concrete Structure …

77

Fig. 5.11 Stress and damage distribution when the maximum settlement is controlled at 18 mm: a stress distribution curve of frame beam on the first floor; b yield proximity distribution curve

Fig. 5.12 The first principal stress cloud diagram of the settlement control standard structure

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5 Quantitative Prediction Method of Building Damage

Fig. 5.13 Stress and damage distribution when the maximum settlement is controlled at 18 mm; a stress distribution curve of frame beam on the first floor; b yield proximity distribution

5.3.2 Blasting Vibration Monitoring Results and Analysis When drilling and blasting through a building, the building is not only affected by surface settlement, but also by blasting vibration. In actual engineering, these two effects should act on the building structure at the same time, and even the impact effect of the blasting wave on the structure is more advanced. However, in order to simplify the calculation, when studying the dual effects of the two factors, this section first applies the settlement disturbance to the structure and then applies the blasting vibration excitation to analyze the influence of the two disturbances on the building structure. The blasting vibration data selected in this chapter comes from the location and distance between the building and the tunnel. Fourteen monitoring points are arranged at intervals of 15.18 m near the building. Three monitoring points are selected from

5.3 The Impact of Blasting Vibration on Concrete Structure …

79

the blasting vibration monitoring results. According to the data, the acceleration time history curve is obtained by differential processing according to the tangential velocity time history curve of these two points, as shown in Fig. 5.14. Under the given conditions of the damping ratio ξ, the absolute acceleration response spectrum can be calculated from the absolute maximum value of the absolute acceleration and the relative velocity response of a series of single-degree-offreedom systems with different natural frequencies under the action of the ground or

Fig. 5.14 Acceleration time history curve: a the horizontal tangential component of the peak vibration velocity is 1.63 cm/s; b the horizontal tangential component of the peak vibration velocity is 2.66 cm/s; c the horizontal tangential component of the vibration peak velocity is 2.79 cm/s

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5 Quantitative Prediction Method of Building Damage

foundation acceleration load. Sa(T) and relative velocity response spectrum Sv(T), see formula (5.10), formula (5.11). Absolute acceleration response spectrum reveals the change law of inertial force response of building structure with natural frequency during ground motion; relative velocity response spectrum reveals the change law of viscous damping force response of building structure with natural frequency during ground motion. | √ √ | (t 2 | 2π 1 − ξ 2 2π 1 − ξ 2 −ξ w(t−τ ) 1 − 2ξ | x¨ g (τ )e [( ) · sin (t − τ ) Sa (T ) = | T 1 − ξ2 T | 0 | √ | 2π 1 − ξ 2 2ξ | cos (t − τ )]dτ | − √ 2 | T 1−ξ max

|( √ | t 2π 1 − ξ 2 | −ξ w(t−τ ) Sv (T ) = | x¨ g (τ )e [cos (t − τ )] | 0 T | √ | ξ 2π 1 − ξ 2 | − √ sin (t − τ )]dτ | 2 | T 1−ξ

(5.10)

(5.11)

max

The response spectrum of blasting vibration acceleration when the damping ratio is 0.05 is shown in Fig. 5.15; the response spectrum of blasting vibration velocity is shown in Fig. 5.16. The absolute acceleration of the main frequency of the response spectrum is between 90 and 120 Hz, and the relative speed response spectrum is between 30 and 50 Hz. The natural frequency of the building is very different from the main frequency of the blasting, and resonance will not occur. According to the monitored blasting acceleration time history curve, the corresponding self-power spectral density function is obtained by using Matlab to compile

Fig. 5.15 Response spectrum of blasting vibration acceleration

5.3 The Impact of Blasting Vibration on Concrete Structure …

81

Fig. 5.16 Blasting vibration velocity response spectrum

the program, as shown in Fig. 5.17. Figure 5.17 can clearly show the power distribution at each frequency of the vibration signal. It can be seen that the main power of this blasting is concentrated between 50–130 Hz.

5.3.3 Damage Prediction Caused by Building Blasting Vibration Input the third blasting vibration acceleration curve to the building structure, and the stress distribution of the structure under the influence of blasting vibration is shown in Fig. 5.18 According to the stress distribution of the building structure under the action of blasting vibration, combined with the yield proximity function (5.5), the damage distribution of the building structure can be quantitatively calculated. Figure 5.19 shows the damage distribution of a frame beam under the action of the first and third blasting vibrations. It can be seen from the figure that when the blasting vibration is affected, the yield proximity is in the range of 0.95 to 1.0. According to the definition of yield proximity in formula (5.6), the impact of blasting vibration on the cracking damage of the building structure is relatively small.

5.3.4 Damage Prediction Due to the Dual Effects of Surface Settlement and Blasting Vibration Due to the drilling and blasting method, the buildings passing through the tunnel will be affected by the ground settlement and the impact of blasting vibration at the same time. Therefore, this section first applies a maximum settlement of 18 mm to the building structure, and then inputs the two blasting vibration acceleration

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5 Quantitative Prediction Method of Building Damage

Fig. 5.17 Self-power spectral density

Fig. 5.18 Stress distribution curve of first-floor frame beam under blasting vibration

5.3 The Impact of Blasting Vibration on Concrete Structure …

83

Fig. 5.19 Yield proximity distribution curve of blasting vibration frame beam

time-history curves to the deformed structure to analyze the cracking damage of the building structure under the superimposition of the two effects. Figure 5.20a is the stress distribution of the first-floor frame beam under the action of the first blasting vibration acceleration time-history curve, and Fig. 5.20b is the cracking damage distribution of the first-floor and top-floor beams. Under the dual influence, the first building The layer and top frame beams appear close to cracking damage in some areas. Comparing Figs. 5.13 and 5.20a, b, it can be seen that the stress distribution and cracking damage distribution of the building structure have changed under the action of ground settlement and under the simultaneous action of the two effects. Although the frequency of the blasting vibration is much higher than the natural frequency of the building, the blasting vibration alone will not cause the cracking damage of the building structure, but the contribution of the blasting vibration of the building structure after settlement to the cracking damage of the building structure cannot be ignored. Figure 5.20c shows the cracking damage of the building under the dual influence of the first type of blasting vibration when the maximum ground settlement is controlled to 15 mm. It can be seen from the figure that the minimum yield proximity of the concrete beam is above 0.20, and no cracking damage will occur. Therefore, when

84

5 Quantitative Prediction Method of Building Damage

Fig. 5.20 Control standard: a stress distribution curve of frame beam on the first floor; b yield proximity distribution curve (18 mm); c yield proximity distribution curve (15 mm)

the maximum settlement is controlled to 15 mm, the dual effects of settlement and blasting vibration will not cause. Cracking damage to be building.

5.4 Conclusion

85

5.4 Conclusion Based on the back analysis of ground settlement prediction based on the measured data, this chapter derives a yield proximity model based on the concrete failure criterion, comprehensively analyzes the damage distribution and evolution process of the building structure under the influence of ground settlement and blasting vibration, and obtains the following conclusions: (1) Through the yield proximity model, the quantitative assessment of the cracking damage of the surface buildings is realized. This method can give specific settlement and blasting vibration control standards for specific buildings on the basis of on-site inspection, and provide guidance for the design and construction of tunnels; (2) According to the random medium theory, the impact angle of surface settlement during tunnel excavation of this type of formation is about, and the tunnel section shrinkage rate of this construction method is about 19.8 mm; (3) If the impact of blasting vibration is not taken into account, when the building settlement is 0–18 mm, the building structure will not suffer from cracking damage, and the impact of the excavation settlement will be small; when the construction control is carried out according to this control standard, the building’s Settlement monitoring points should be arranged on the main structure, and the monitoring points arranged on the enclosure structure cannot reflect the real structural deformation; when the settlement of the building is greater than 18 mm, cracking damage will occur in some areas of the building structure, although the damage area cannot be determined However, it can be determined that the structural cracks have the risk of exceeding the specification limit; (4) When considering the impact of blasting vibration, the maximum settlement of the building should be controlled at 15 mm, otherwise the dual effects of ground settlement and blasting vibration will cause cracking and damage in some areas of the building; (5) Since the frequency of blasting vibration is quite different from the natural frequency of the building itself, the damage to the building structure caused by blasting vibration is small. According to the research results of the engineering examples in this section, the blasting vibration whose vibration velocity is less than a certain value alone will not cause obvious cracking damage to the concrete structure. Taking into account the stability of the overlying reinforced stratum of the subway tunnel, the existing quality of the main building structure, the safety of the auxiliary structure of the building, and other influencing factors, the controlled vibration speed should also be divided by a comprehensive safety factor.

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5 Quantitative Prediction Method of Building Damage

References 1. Zhang M (2007) Research on urban underground space development plan coordinated with environment. Qingdao Technological University, Qingdao 2. Ottosen NS (1977) A failure criterion for concrete. J Eng Mech Div 103(4):527–535

Chapter 6

Risk Management of Crossing Buildings in Tunnel Construction

The construction of urban tunnels through buildings is a complex and high-risk system engineering [1, 2]. From a macro perspective, establishing a complete safety risk management system for the whole process and all-round, and implementing dynamic management of the whole process of tunnel construction is the main way to solve the frequent occurrence of building damage accidents [3]. Based on the analysis of the basic mechanical problems and risk management objectives of urban underground engineering, this chapter combines engineering practice, and from a systematic point of view, the general procedure for the safety risk management of urban tunnel construction through buildings is proposed, and the construction of the buildings contained in it is explained in detail. The main work content of five aspects: current situation assessment and safety evaluation, tunnel construction plan optimization, construction process control, process monitoring, and post-construction evaluation and recovery, emphasizing the systematic control of building safety from the level of technical operability Therefore, a safety risk management system for tunnel construction through buildings is constructed. The system has been used to guide engineering practice and has achieved good results. It is also expected to further deepen and improve on basic theoretical research, quantitative analysis and operation refinement.

6.1 Risk Management Objectives 6.1.1 Environmental Safety Management Classification of Rail Transit Engineering Construction The environmental safety of Beijing rail transit project construction adopts a hierarchical management system, which is classified according to the engineering experience and with reference to the following qualitative regulations [4]: © China Architecture Publishing & Media Co., Ltd. 2022 D. Meng et al., Prediction and Control of Interaction Between Ground Building and Tunnel Construction Process, https://doi.org/10.1007/978-981-19-3474-2_6

87

88

6 Risk Management of Crossing Buildings in Tunnel Construction

(1) Super environmental safety risk: Refers to a new construction project underneath existing track lines (including railways). (2) Level 1 environmental safety risk: Refers to new constructions that pass under existing buildings (structures) and over pass existing tracks. (3) Secondary environmental safety risk: Refers to new constructions adjacent to existing buildings (structures) that pass through important municipal pipelines and rivers. (4) Level 3 environmental safety risk: Refers to new construction projects that pass through general municipal pipelines and other municipal infrastructure. In a specific project, combining the characteristics of the project and the environment, and on the basis of full investigation and analysis, the environmental safety risk of a certain level can be appropriately raised or lowered by one level.

6.1.2 Fundamental Mechanical Problems and Safety Risk Management Objectives of Tunnel Engineering The risk management goal is based on environmental safety risk control, involving the safety control of existing buildings such as surface buildings, underground pipelines and existing lines, and focusing on basic mechanics issues to set corresponding risk management goals [4], as shown in Fig. 6.1. Moreover, the impact of underground engineering construction on the environment is a complex interactive process and a continuous cycle process, which requires risk management to have dynamic characteristics. Therefore, in view of potential risks, the use of dynamic risk management methods can effectively control the impact of subway tunnel construction on the environment [5–7].

6.2 Risk Management System The construction safety risk management system for tunnel crossing existing buildings is embodied in the workflow shown in Fig. 6.2. According to this workflow, the general procedure for safety risk management of urban tunnel construction through important buildings is shown in Fig. 6.3.

6.2 Risk Management System

89

Management goal

Basic problem

Formation deformation model and mechanism

Engineering structure and environmental risk control Safety control of surface buildings

Formation deformation propagation law and distribution

Underground pipeline safety control

Formation failure mode

Dynamic interaction model of stratum and structure

Safety risk manage

Security control of existing lines

Force characteristics of buildings

Surface traffic safety control

Stratum Deformation Control Technology

Safety control of engineering support structure

Mechanism of groundwater's influence on construction safety

Safety control during construction

Fig. 6.1 Basic problems and risk management objectives of subway tunnel engineering

6.2.1 Pre-construction Investigation and Assessment of the Current Situation of the Building and Risk Classification Before construction, it is necessary to identify the risk level of buildings within the scope of the subway tunnel construction to facilitate construction safety and cost control. The first step in the risk classification of a building is to conduct an investigation and safety assessment as the main consideration for risk classification. The current situation investigation and safety assessment of the building are mainly based on the following aspects: (1) The basic survey results of the building, including the importance of the building, the design service life, the construction year, the structure type, the number of floors, the use, the total height, the foundation form, the relative position relationship with the tunnel, and the surrounding area under the building. The type of rock and other hydrogeological conditions; (2) A safety appraisal report from an authoritative engineering quality inspection and appraisal agency, which should include structural calculation analysis and seismic analysis check calculations.

90

6 Risk Management of Crossing Buildings in Tunnel Construction Building status assessment and safety assessment, including risk classification and grading, and formulate corresponding control standards Based on the analysis of additional construction impacts, realize the optimization of the construction plan, including the optimization of the construction method and auxiliary method, thereby determining the construction plan with the leastimpact on the environment Predict the impact of the proposed construction plan on the safety of the building, conduct a safety risk assessment by comparing with the control standard, and obtain the risk management level

When the evaluation result shows that the construction cannot guarantee the safety requirements of the building, the building should be reinforced to improve the anti-deformation ability

Decompose the deformation control standards in stages according to the characteristics of the tunnel construction process, and determine the stage control objectives and process control plans

The formulation and implementation of monitoring and measurement programs for important buildings, and timely program adjustments based on monitoring results, including construction methods and auxiliary construction measures, to meet stage control requirements

When the phase control target cannot meet the requirements, the "process recovery" method can be adopted to meet the overall control requirements

After the completion of construction, re-evaluate the key buildings, determine the necessity of structural restoration according to the degree of damage, and formulate specific restoration plans and measures when necessary

Fig. 6.2 Risk management workflow

Through the understanding of the basic conditions of the building, combined with the construction plan of the subway tunnel, and based on the monitoring data of onsite ground deformation and groundwater, the degree of foundation deformation of the building is predicted, and the response of the building under this additional load is checked. Comprehensive consideration of various factors, the use of fuzzy evaluation methods and other means to classify the risk level of the building.

6.2.2 Establishment of Safety Control Standards for Buildings The actual project construction process, we will divide different control standards for different risk objects, which is not only conducive to the control of construction risks, but also has strong operability. Therefore, the importance of the building, the building’s own characteristics (structure type, number of floors, use, total height, foundation form) and the relative position relationship with the tunnel are all the

6.2 Risk Management System

91 Simulation of impact of tunnel construction

Building date research

Measured data back analysis parameters

Construction status, conditions

Work status

Tunne date

Geology status

Acceptance/observation records

Incident handling report

Reinforcement plan

Engineering Geology Report

Design and as-built drawing

Settlement prediction

On-site inspection Construction deformation prediction value

Anti-deform ation ability

Carrying capacity calculation

Safety rating

Risk classification

The relation ship between the building and the tunnel location

N

S ≤P

Improve methods process recovery Y

N Improve reinforcent effect

Step-by-step control scheme

Step-by-step control value Ci for each stage

Monitoring value Mi during the construction phase of step i

i=1

Mi ≤Ci

N

Mi ≤ Ci

Y i=i+1

Y

i≤n

N Y

Analyze the reasons and take measures

Fig. 6.3 Risk management procedures for tunnel construction through buildings (structures)

basis for the formulation of its safety control standards. The establishment of building safety control standards specifically includes the following steps: (1) Taking buildings and tunnels as the overall consideration, establish a numerical analysis model or a theoretical analysis model. The model should include the

92

6 Risk Management of Crossing Buildings in Tunnel Construction

construction age characteristics of the building, the existing strength characteristics, the existing quality defects, and the location relationship with the tunnel, Surrounding rock grades and other hydrogeological conditions. (2) Analyze the impact of the tunnel excavation process on the building as a whole, and simulate the tunnel excavation process, analyze the impact of the ground deformation load on the building, and then calculate and analyze the response of the structure with different characteristics to the additional load, according to the response of the structure The characteristics of the development of response safety control standards. (3) With reference to existing norms and standards, considering a certain safety factor, formulate control standard values for different buildings as the basis for construction.

6.3 Application of Urban Tunnel Crossing Building Risk Management Engineering 6.3.1 Investigation, Inspection and Appraisal of Buildings Along the Tunnel In order to faithfully grasp the structural form, foundation form, construction age and relative position relationship with the tunnel of a certain subway tunnel through key buildings, especially its existing quality conditions (if there are any problems due to construction quality, uneven foundation settlement, temperature Building damage caused by cracks, improper use, long-term disrepair, etc.), correctly evaluate the antideformation ability of the building, calculate the allowable deformation value of the building, scientifically determine the settlement control standard and blasting vibration control standard of the building, and propose a scientific The surface settlement control measures and blasting vibration control measures are used to guide the safe construction of subway tunnels. Before the construction of the subway tunnel, the inspection and identification of 20 key buildings in the 3 key sections of the tunnel crossing (Tables 6.1, 6.2 and 6.3, status quo See Appendix B) for photos and other information. The main contents of the appraisal are: (1) Conduct on-site inspections of the building’s basic form, structural form, structural layout, and material strength of building structural components, and identify the parts or problems with potential safety hazards; (2) On-site survey or measurement of the uneven settlement of the building foundation or the inclination of the building; (3) On the basis of on-site inspection, scientifically evaluate the existing quality of the building, and estimate the ability of the building to resist surface deformation and blasting vibration;

6.3 Application of Urban Tunnel Crossing Building …

93

Table 6.1 Statistical table of building appraisal results in section 1 Building number

Time

Building floors and basement

Building structure

Form of foundation

Vertical distance (m)

Rock grade

Safety grade

Risk grade

1

1994

1 floor underground 3 floors above ground

Framework

Rubble strip

Under 13.9

IV–V

Bsu

I

2

1994

As above

Framework

As above

Under 11.8

IV

Csu

I

3

1992

9 floors

Framework

As above

Under 14.3

IV

Bsu

I

Table 6.2 Statistical table of building appraisal results in Ling–Qing section Building number

Time

Building floors and basement

Building structure

Form of foundation

Vertical distance

Rock grade

Safety grade

Risk grade

1

20th 80’s

4 floors

Mixed structure

Rubble strip

under 11.3 m

IV

Csu

II

2

1986

6 floors

Mixed brick structure

As above

under 10.7 m

IV

Csu

II

3

1986

6 floors

As above

As above

under 10.4 m

IV

Csu

II

4

1986

6 floors

As above

As above

under 10.4 m

IV

Csu

II

5

1994

7 floors Bottom Partially 2 frame structure floors

Independent column base

flank 12.6 m

II

Csu

III

6

2004

6 floors Partially1 floors

Bottom frame structur

Pile

Under 5.1 m

V

Bsu

II

7

2001

6 floors

Bottom frame structur

As above

Under 4.6 m

V

Bsu

III

8

2001

6 floors

Bottom frame structur

As above

Under 6.8 m

V

Bsu

II

9

2001

6 floors

Bottom frame structure

As above

Flank 3.0 m

III

Bsu

III

10

1995

7 floors

Mixed brick structure

Rebar concrete

Under 16.7 m

V

Bsu

II

94

6 Risk Management of Crossing Buildings in Tunnel Construction

Table 6.3 Statistical table of building appraisal results in section 3 Building Time Building number floors and basement

Building structure

Form of foundation

Vertical Rock Safety Risk distance grade grade grade

1

1994 1 floor framework Rammed pipe underground pile 3 floors above ground

Under 13.9 m

VI

Bsu

I

2

1994 As above

framework As above

Under 11.8 m

VI

Bsu

I

3

1992 9 floors

framework rebar concrate

Under 14.3 m

VI

Bsu

III

4

2003 7 floors

bottom frame structure

Depend Structure

Flank 14.3 m

VI

Bsu

I

5

1995 5 floors

Mixed brick structure

Rubble strips

Under 13.0 m

VI

Csu

I

6

1994 6 floors

Mixed Structure

Rubble strips

Under 12.5 m

VI

Bsu

I

7

2003 6 floors, Partially 7 floors have basement

Mixed Structure

Depend Under Structure/rebar 10.9 m concrate

VI

Bsu

I

(4) Predict the impact of ground settlement and blasting vibration caused by underground tunnel construction on the building; (5) Give an appraisal opinion to the building, determine its safety level, and put forward scientific ground settlement control countermeasures and blasting vibration control countermeasures. Among them, an appraisal report was issued on the safety of a typical building. The appraisal report is different from the traditional building safety appraisal report, mainly because the report fully considers the characteristics of the surrounding rock of the tunnel and the relative position relationship between the building and the tunnel, and provides theoretical support for the next step of building risk classification.

6.3.2 Relative Position Relationship Between Subway Tunnel and Building (1) The relationship between the plane and space position of the building and the tunnel in section 1

6.3 Application of Urban Tunnel Crossing Building …

95

The buildings that will be under construction in the Taiyan section are the Yimeier Plastic Surgery Hospital, No. 20, Hong Kong West Road, No. 22 Home Inn Hotel Taipingjiao, No. 26, the Department of Stomatology, the First Sanatorium of Jinan Military Region, and the private house of No. 3 Zhanshan Road. The relative positional relationship between buildings and tunnels in plane and space is shown in Fig. 6.4 and 6.5.

Fig. 6.4 Relationship between horizontal position of the building and the tunnel in section 1

96

6 Risk Management of Crossing Buildings in Tunnel Construction

Fig. 6.5 Spatial relationship between the building and the tunnel in section 1

(2) The relationship between the plane and space position of the building and the tunnel in section 2 Figures 6.6, 6.7, 6.8 and 6.9 shows the relative position relationship between the crossing building and the tunnel during Lingqing section construction. (3) The horizontal position relationship between the building and the tunnel in section 3

Fig. 6.6 Building size and the location of the tunnel in section 2(1)

6.3 Application of Urban Tunnel Crossing Building …

Fig. 6.7 Spatial relationship between buildings and tunnels in section 2(1)

Fig. 6.8 Relationship between the building and the tunnel plane position in section 2(2)

97

98

6 Risk Management of Crossing Buildings in Tunnel Construction

Fig. 6.9 Relationship between the building and the tunnel plane position in section 2(3)

The plane position relationship between the building and the tunnel passing through section 3 is shown in Fig. 6.10. The influence of tunnel excavation spreading outward gradually attenuates with the increase of distance, so the farther the building is from the tunnel, the less the influence will be. Based on the actual engineering situation of the above-mentioned three section tunnels passing through the building, this section uses the 50 m building red line at the outer edge of the tunnel structure and the edge of the double-line tunnel structure as the boundary. Adjacent, adjacent, relatively adjacent, non-adjacent 4 levels.

6.3.3 Building Risk Classification (1) The division of building safety grade and the selection of judging elements Building structure type, foundation form, aspect ratio, body shape, existing quality conditions, etc. are all influencing factors for the classification of building risk levels. In addition, the characteristics of subway tunnels (such as the way the subway crosses the building, the tunnel vault to the foundation The distance, the engineering geological conditions of the building, the tunnel excavation and support methods, etc.) are also important factors affecting the classification of risk levels. Due to the large number of buildings involved and the large difference in risk, in order to meet the needs of the project, the risks of the buildings are divided into five levels: large, large, general, small, and small, respectively I, II, and III, IV and V grades are indicated as shown in Table 6.4. The corresponding influencing factors and classification are shown in Table 6.4. (2) Determine the membership function of relevant factors Generally, there are two main methods for selecting the membership function. One is to use fuzzy statistics to compare the statistical curve with the fuzzy distribution

6.3 Application of Urban Tunnel Crossing Building …

99

Fig. 6.10 Relationship between the 3rd crossing building and the tunnel plane position

curve to find the most similar distribution; the other is to select according to the characteristics of the research object. For quantitative indicators, membership functions can be selected to determine the degree of membership for different evaluation levels. For buildings, where qualitative indicators are mostly, they can be converted into quantitative indicators by fuzzy mathematics. This article uses ridge-shaped membership functions to describe quantitative indicators [8–10], and the distribution of membership functions is as follows:

Good

Fine

IV

V

Fine

Good

Medium

Bad

Fine

Good

Medium

3.0–3.7

< 2.0

2.0–2.5

2.5–3.0 Fine

Good

Medium

Bad

Inferior

Fine

Good

Medium

Bad

Inferior

Bad

Bad

Medium

II

> 3.7

Inferior

Inferior

Inferior

Relative position

Figure

Influence section Aspect ratio

Foundation

Quality

Struture

Building form

III

I

Building risk grade

Table 6.4 Affecting factors and evaluation grade table

Fine

Good

Medium

Bad

Inferior

Geological condition

> 30

20–30

15–20

10–15

< 10

Buried depth

Fine

Good

Medium

Bad

Inferior

Dig and support method

100 6 Risk Management of Crossing Buildings in Tunnel Construction

6.3 Application of Urban Tunnel Crossing Building …

μI =

⎧ ⎪ ⎨1 1 2

⎪ ⎩0

⎧ ⎪ 0 ⎪ ⎪ ⎨1

− sin 1 2

2π (b−a)

(

(

x−

3a+b 4

)

101

)x ≤a a < x ≤ (a+b) 2/ x > (a + b) 2 x ≤a

3a+b a < x ≤ (a+b) 4 2 ) a+2b+c (a+b) < x ≤ (b+c) 2 2 / 2

− + sin 2 1 ⎪ − − sin ⎪ 2 ⎪ ⎩ 0 x > (b + c) 2 ⎧ / ⎪ 0 x ≤ (a + b) 2 ⎪ ( ) ⎪ ⎨ 1 + 1 sin 2π x − a+2b+c (a+b) < x ≤ (b+c) (c−a) ( 2 2 2 ) (b+c) μI∥ = 21 21 (c+d) 2π ⎪ 2 − 2 sin (d−b) x − b+2c+d < x ≤ ⎪ 2 2 ⎪ / 2 ⎩ 0 x > (c + d) 2 ⎧ / ⎪ 0 x ≤ (b + c) 2 ⎪ ( ) ⎪ ⎨ 1 + 1 sin 2π x − b+2c+d (b+c) < x ≤ (c+d) (d−b) ( 2) 2 2 μIV = 21 21 (c+d) 2π ⎪ x − c+3d − 2 sin (d−c) d ⎧ / ⎪ 0 ( x ≤ (c + d) 2 ⎨ ) (c+d) 1 2π c+3d 1 d μ∥ =

1 2 1 2

2π x (b−a) ( 2π x (c−a)

(6.1a)

(6.1b)

(6.1c)

(6.1d)

(6.1e)

where a, b, c, d are the 5 intervals corresponding to evaluation factors and comments (−∞, a], (a, b], (b, c], (c, d], (d, +∞), The corresponding comment is very serious (v1 ), serious (v2 ), just so so (v3 ), slight (v4 ), 和no influence (v5 ). Slightly aiming at the buried depth of the tunnel, according to the actual buried depth of Qingdao Metro, define a = 10, b = 15, c = 20, d = 30 and express its membership function as: ⎧ x ≤ 10 ⎨1 μI = 21 − 21 sin 0.4π(x − 11.25) 10 < x ≤ 12.5 (6.2a) ⎩ 0 x > 12.5 ⎧ 0 x ≤ 10 ⎪ ⎪ ⎨1 1 + sin 0.4π(x − 11.25) 10 < x ≤ 12.5 μII = 21 21 (6.2b) ⎪ − sin 0.2π(x − 30) 12.5 < x ≤ 17.5 ⎪ ⎩2 2 0 x > 17.5 ⎧ 0 ⎪ ⎪ ( ) x ≤ 12.5 ⎨1 1 2π 60 + sin 10 (x − 2 ) 12.5 < x ≤ 17.5 μIII = 21 21 (6.2c) ⎪ x − 85 17.5 < x ≤ 25 − sin 2π ⎪ 15 2 ⎩2 2 0 x > 25

102

6 Risk Management of Crossing Buildings in Tunnel Construction

⎧ 0 ⎪ ⎪ ⎨1

+ sin 2 1 ⎪ − sin ⎪ ⎩2 0 ⎧ ⎨0 μV = 21 − 21 sin ⎩ 1

μIV =

1 2 1 2

(

2π 10

(

) x ≤ 17.5 17.5 < x ≤ 25 25 < x ≤ 30 x > 30

(6.2d)

) x ≤ 25 25 < x ≤ 30 x > 30

(6.2e)

− −

85 2 ) 110 4

x−

110 4

2π x 15 ( 2π x 10

According to the definition of the length-to-height ratio of the research object in this chapter, aiming at the length-to-height ratio of the building, defining a = 3.5, b = 3, c = 2.5, d = 2, the membership function is expressed as: μI =

⎩

1 2

(

− 21 sin

2π 13.5 0.5 4

0

⎧ 0 ⎪ ⎪ ⎨1

+ 2 1 ⎪ − ⎪ ⎩2 0 ⎧ ⎪ ⎪ ⎨1 + = 21 ⎪ − ⎪ ⎩2

μII =

μIII

⎧ ⎨1

1 2 1 2

sin sin

1 2 1 2

) x ≥ 3.5 − x 3.25 ≤ x < 3.5 x < 3.25 ) x ≥ 3.5 3.25 ≤ x < 3.5 2.75 ≤ x < 3.25 x < 2.75

(6.3b)

0 ( x ≥ 3.25 ) 2π 12 − x 2.75 ≤ x < 3.25 1 ( 2 ) 2π 10 − x 2.25 ≤ x < 2.75 1 2 0 x < 2.25

(6.3c)

(

2π 13.5 − )x 0.5 ( 4 2π 12 − x 1 2

sin sin

(6.3a)

⎧ 0 ⎪ ⎪ ⎨1

( ) x ≥ 2.75 1 2π 10 + sin − x 1 (2 ) 2.25 ≤ x < 2.75 μIV = 21 21 2π 8.5 ⎪ 2 − 2 sin 0.5 4 − x 2 ≤ x < 2.25 ⎪ ⎩ 0 x 0.45 ⎧ ⎪ 0 x < 0.35 ⎪ ⎪ ⎪ ⎪ ⎨ 10x − 3.5 0.35 < x ≤ 0.45 μIII = 1 0.45 < x ≤ 0.55 ⎪ ⎪ ⎪ 6.5 − 10x 0.55 < x ≤ 0.65 ⎪ ⎪ ⎩0 x > 0.65 ⎧ ⎪ 0 x < 0.55 ⎪ ⎪ ⎪ ⎪ ⎨ 10x − 5.5 0.55 < x ≤ 0.65 μIV = 1 0.65 < x ≤ 0.75 ⎪ ⎪ ⎪ 8.5 − 10x 0.75 < x ≤ 0.85 ⎪ ⎪ ⎩0 x > 0.85 ⎧ x ≤ 0.75 ⎨0 μV = 10x − 7.5 0.75 < x ≤ 0.85 ⎩ 1 x > 0.85

103

(6.4b)

(6.4c)

(6.4d)

(6.4e)

In order to make a single-factor evaluation of u i (i = 1, 2, · · · , m) From the influencing factor u i , determine the degree of membership ri j of the thing to the judgment level V j ( j = 1, 2, · · · , n). In this research, u represents the building’s own factors and the influencing factors of subway engineering, and from this, the single factor judgment set of u i . ˜ = {r i1 , ri2 , ri3 , ri4 , ri5 } the judgment set r ij = r i1 ,r i2 ,…,r i5 is a fuzzy subset of R V, the fuzzy relationship can be constructed from the evaluation set of m influencing factors: ⎤ ⎡ u 11 · · · u 15 . . ⎥ ˜ =⎢ (6.5) R ⎣ .. . . . .. ⎦ u 91 · · · u 95

In the formula, μi j is the i membership degree of the factor index to the j level. (3) Judging the safety level of the building Taking the buildings appearing in Sect. 5.1.1 as the research object, the fuzzy comprehensive assessment of the safety risks of the tunnel excavation is carried out. Determine the weight of each evaluation factor to the evaluation object, establish a comprehensive evaluation set, which can be expressed as a judgment matrix according to the judgment level, and the specific judgment matrix is formula (6.6).

104

6 Risk Management of Crossing Buildings in Tunnel Construction

The first-level fuzzy comprehensive evaluation is performed and normalized, and the resulting evaluation set is: B˜ = {0.36, 0.13, 0.01, 0.45, 0.05}. According to the principle of maximum membership degree, it can be seen that the safety risk level of the building is IV, which means that the risk of the building is low, and the building needs simple protection before construction and minor repairs. Similarly, the abovementioned evaluation method system can be used to analyze, evaluate and classify the safety risks of other buildings. Finally, the relevant parameters and risk levels of the remaining 19 buildings are shown in Tables 6.1, 6.2 and 6.3. ⎡

0 ⎢0 ⎢ ⎢0 ⎢ ⎢0 ⎢ ⎢ R(H ) = ⎢ 0 ⎢ ⎢1 ⎢ ⎢1 ⎢ ⎣0 0

0 0 0 0 0 0 0 0.29 1

0 0 0 0 0 0 0 0.71 0

1 1 1 0 1 0 0 0 0

⎤ 0 0⎥ ⎥ 0⎥ ⎥ 1⎥ ⎥ ⎥ 0⎥ ⎥ 0⎥ ⎥ 0⎥ ⎥ 0⎦ 0

(6.6)

6.3.4 Building Settlement Control Standard (1) Specification analysis and amendment Article 5.3.4 of the ‘Code for Design of Building Foundation’ (GB50007-2011) clearly stipulates the allowable value of foundation deformation during the service period of the building (Tables 6.2, 6.3 and 6.4). The currently adopted tunnel excavation-induced building tilt control standard ‘0.003’ is determined based on the ‘overall tilt of multi-storey and high-rise buildings (24 < Hg ≤ 60)’ in the code. According to the definition of the code, it represents the limit of the amount of inclination of the building during the ‘construction process + the entire service period’. As we all know, in the early stage of building construction, the building itself has an overall tilt, and as the use time extends, its overall tilt will gradually increase. The tilt of the building caused by tunnel excavation can only be part of the building tilt control standard ‘0.003’, otherwise it will cause the tilt of the building to exceed the specification limit. Therefore, at present, the control standards for the inclination or differential settlement of buildings caused by the construction of the Qingdao subway tunnel need to be further improved. Based on the preliminary research summary of this research group, combined with the impact of subway tunnel construction, we define the overall tilt of the building as three stages: front, middle, and rear. The stage “before” refers to the process in which the building is tilted before the tunnel excavation is affected, and the amount of tilt in this stage accounts for 30%

6.3 Application of Urban Tunnel Crossing Building …

105

of the total tilt of the building; the stage ‘in’ refers to the process in which the building is tilted due to the influence of the tunnel excavation, The inclination at this stage accounts for 30% of the total inclination of the building; the ‘post’ stage refers to the process of building inclination after the tunnel is excavated, and the inclination at this stage accounts for 40% of the total inclination of the building. According to this standard, we revised the allowable value of foundation deformation of buildings affected by Qingdao Metro excavation to Table 6.5 (Fig. 6.11). (2) Deformation resistance of buildings based on on-site inspection and appraisal In order to truthfully grasp the existing quality of the building (such as whether there is building damage caused by building quality, uneven foundation settlement, temperature cracks, improper use, long-term disrepair, etc.), correctly evaluate the anti-deformation ability of the building and determine the building Allowable deformation value, scientifically determine the settlement control standard and blasting vibration control standard of the building, and guide the safe construction of the subway tunnel. This study conducts inspection and identification of the involved buildings before the subway tunnel construction. One building identified by the on-site inspection has 5 floors above ground and 1 floor underground. The top elevation of the basement floor is −2.5 m. The whole is arranged in an L shape, and the lengths of the two sides are 32.3 m and 38.6 m respectively. The storey height is 4.2 m, and the total height is 21 m. It occupies an area of 1518 m2 , with a building area of 5897 m2 , and the certified area of this time is 5897 m2 . The main structure of the building is a mixed structure of reinforced concrete frame structure and masonry load-bearing part. The outer wall is a masonry loadbearing structure, and the rest is a reinforced concrete frame structure with cast-in-situ reinforced concrete floor slabs. The basement floor, wall and roof are all reinforced concrete pouring, and the wall thickness is 250 mm. The foundation form under the frame column of the building is an independent foundation with a depth of −2.0 m. The foundation under the wall is a cement mortar masonry ashlar strip foundation, and the strip foundation and the column base are all cement mortar masonry rubble. After a comprehensive site survey, testing, monitoring, and scientific verification and appraisal, the following appraisal conclusions were obtained for the building: (1) There is no obvious uneven settlement of the foundation, the foundation is relatively stable, and the bearing capacity is sufficient. According to the design drawings, the foundation is the ashlar strip foundation and the independent foundation under the column; (2) The structure of the building is a frame-masonry mixed structure; (3) The material strength is low, among which the compressive strength of masonry mortar is estimated to be 0.6 MPa, and the strength of concrete is estimated to be C20; (4) The safety level of the building is Bsu.

106

6 Risk Management of Crossing Buildings in Tunnel Construction

Table 6.5 Allowable values of foundation deformation of buildings affected by Qingdao subway excavation Structure

Masonry load-bearing

Foundation

Correction value Medium and low compressibility soil

High compressibility soil

0.0006

0.0009

Settlement difference of adjacent pile foundation/(mm)

0.00021 L

0.0003 L

As above

0.0006 L

0.0009 L

Partial tilt of the foundation

0.0006

0.0009

Settlement difference of adjacent pile foundation/(mm)

0.0015 L

0.0015 L

Pile foundation

Strip foundation

Partial tilt of the foundation

< 0.0006

< 0.0009

Depend foundation

Settlement difference of adjacent pile foundation/(mm)

< 0.00021 L

< 0.0003 L

Bar Masonry Pile foundation

Framework

Deformation characteristics

Depend t

Partial tilt of the foundation As above

Pile Raft Fabricated strip A structure that does not generate additional stress when the foundation settles unevenly * Bottom frame masonry structure

Overall tilt of multi-story and high-rise buildings

Depend

Hg ≤ 24 24 < Hg ≤ 60 60 < Hg ≤ 100 Hg > 100

0.0012 0.0009 0.00075 0.0006

Note 1. * The multi-layer masonry structure of the bottom frame is very sensitive to uneven settlement and should be investigated 2. On-site investigations should be conducted on important structures, and the allowable amount of deformation should be determined according to their use requirements. 3. All the above control standards are based on 60% early warning and 80% alert

6.3 Application of Urban Tunnel Crossing Building …

107

Fig. 6.11 Distribution principle of allowable deformation value of building foundation. Note Different buildings have different proportional distributions, and scientific distribution should be given according to the building appraisal results

In this study, combined with the conclusions of building appraisal, the recommended values of settlement and blasting vibration control standards for a certain commercial building are given, which are listed in Table 6.6. Comprehensive use of existing code analysis and revision of on-site inspection and appraisal conclusions of buildings, combined with the building numerical simulation and damage theory analysis used in Chapter 5 of this book, this chapter studies the development of relevant control standards for key buildings that a subway tunnel passes through. See Table 6.7. This standard has been scientifically applied and tested in practice during the on-site construction process.

6.3.5 Building Blasting Vibration Control Standard During the construction of subway tunnels, blasting construction should be carried out in strict accordance with the “Blasting Safety Regulations”. When selecting the safety allowable vibration speed of the building, the importance of the building, the quality of the building, the degree of new and old, the frequency of natural vibration, and the foundation conditions should be comprehensively considered. As shown in Table 6.8. According to the repeated disturbance of the ground by the blasting vibration of Qingdao Metro Line 3, the ‘Blasting Safety Regulations’ were adjusted accordingly based on the analysis of the field measured data and the damage of the buildings, and various types of buildings involved along the Qingdao Metro were obtained. Blasting vibration control standards (Table 6.9).

20

Commercial building

≤ 1.0

Blasting control standards (cm/s)

Basis for Standard Formulation (1) The masonry structure controls the deformation of the building according to the local tilt of the building foundation; the frame structure and the bottom frame structure control the deformation of the building according to the settlement difference of adjacent column foundations; the multi-story and high-rise buildings also consider the overall tilt. Control the deformation of the building (2)The actual final deformation allowable value of the building foundation specified in the “Code for Design of Building Foundation” (GB50007-2002); (3) Allowable deformation value of the building inferred according to the existing quality condition of the building; (4) The deformation of the foundation of the building measured on site; (5) The plane and spatial position relationship between the building and the tunnel; (6) The surrounding rock grade of the subway tunnel under the building; (7) The volume and purpose of the building; (8) The protection level of the building (continued)

Standard Instructions (1) The “settlement control standard” is the cumulative settlement of a single measuring point on the building; (2) “Differential settlement” refers to the settlement difference between two adjacent points along the cross section of the tunnel (the settlement difference between the two columns in the figure below);

10

Settlement control standard (mm) Differential settlement control standard (mm)

Building name

Table 6.6 Recommended values of settlement and blasting vibration control standards

108 6 Risk Management of Crossing Buildings in Tunnel Construction

Suggestions (1) Strictly control the amount of ground settlement, the amount of deformation of the building and the charge of a single blasting section during the construction of the subway tunnel; (2) Carry out construction in strict accordance with the building settlement and blasting vibration control standards proposed by the design and other parties; (3) Accurately grasp the foundation type and buried depth of the building; (4) Conduct on-site monitoring of the building during the construction process, and grasp the impact of tunnel construction on the building in time, so as to adjust the construction method and construction schedule in a timely manner, and take targeted protection measures for the building; (5) Strengthen the monitoring of structural cracks in the building when passing through the tunnel

Table 6.6 (continued)

6.3 Application of Urban Tunnel Crossing Building … 109

110

6 Risk Management of Crossing Buildings in Tunnel Construction

Table 6.7 Recommended values of control standards for a subway tunnel passing through key buildings Interval 1 Building number

Settlement control standard (mm)

Differential settlement control standard (mm)

Blasting control standards (cm/s)

1

20

10

≤ 1.0

2

20

15

≤ 1.0

3

25

20

≤ 2.0

1

15

10

≤ 1.0

2

15

10

≤ 1.0

3

15

10

≤ 1.0

4

15

10

≤ 1.0

5

10

5 (adjacent columns)

≤ 1.0

6

10

5 (adjacent columns)

≤ 1.0

7

15

10

≤ 1.0

8

10

5 (adjacent columns)

≤ 1.0

9

10

5 (adjacent columns)

≤ 1.0

10

10

5 (adjacent columns)

≤ 1.0

1

10

5 (adjacent columns)

≤ 1.0

2

10

6 (adjacent columns)

≤ 1.0

3

15

10 (adjacent columns)

≤ 1.0

4

15

6( adjacent columns)

≤ 1.0

5

15

10***

≤ 1.0

6

15

8 (adjacent columns)

≤ 1.0

7

15

6

≤ 1.0

Interval 2

Interval 3

Standard Instructions (1) The “settlement control standard” is the cumulative settlement of a single measuring point on the building; (2) “Differential settlement” refers to the settlement difference between two adjacent points along the cross section of the tunnel; (3) “***” refers to the settlement difference between the measurement point directly above the center line of the tunnel along the direction of the tunnel cross section and the measurement point 10 m away from this point (continued)

6.4 Conclusion

111

Table 6.7 (continued) Basis for Standard Setting (1) The masonry structure controls the deformation of the building according to the local tilt of the building foundation; the frame structure and the bottom frame structure control the deformation of the building according to the settlement difference of adjacent column foundations; the multi-story and high-rise buildings also consider the overall tilt Control the deformation of the building (2) The actual final deformation allowable value of the building foundation specified in the “Code for Design of Building Foundation Foundation” (GB50007-2002); (3) Allowable deformation value of the building inferred according to the existing quality condition of the building; (4) The deformation of the foundation of the building measured on site; (5) The plane and spatial position relationship between the building and the tunnel; (6) The surrounding rock grade of the subway tunnel under the building; (7) The volume and purpose of the building; (8) The protection level of the building Suggestions: (1) Strictly control the amount of ground settlement, the amount of building deformation, and the charge of a single blasting section during the construction of the subway tunnel (2) The construction shall be carried out in strict accordance with the building settlement and blasting vibration control standards proposed by the design and other parties (3) Accurately grasp the foundation type and buried depth of the building (4) Conduct on-site monitoring of the building during the construction process, and grasp the impact of tunnel construction on the building in time, so as to adjust the construction method and construction schedule in a timely manner, and take targeted protection measures for the building (5) Strengthen the monitoring of structural cracks in the building when the tunnel is crossing

6.4 Conclusion Based on the dynamic management thought of the whole process, this chapter constructs the safety risk management system of urban tunnel construction crossing buildings, and proposes the implementation procedure of safety risk management with five steps as the main body; the risk management system has passed the Qingdao Metro The test of the first-phase project practice has achieved remarkable results, and has guiding significance for the environmental safety risk control of urban underground engineering construction. For the key protected cultural relics, the risk management process includes the safety appraisal and risk classification of the building before the tunnel crossing, the safety appraisal and the risk management effect evaluation after the tunnel crossing, and the safety appraisal report of a cultural relic building before and after the tunnel crossing. See Appendix C and Appendix D.

112

6 Risk Management of Crossing Buildings in Tunnel Construction

Table 6.8 Building safety permitted vibration speed Number

Protection object category

Safe allowable vibration speed (cm/s) < 10 Hz 10–50 Hz

50–100 Hz

1

Earth cave dwellings, adobe houses, rubble houses

0.5–1.0

0.7–1.2

1.1–1.5

2

General brick buildings, large non-seismic block 2.0–2.5 buildings

2.3–2.8

2.7–3.0

3

Reinforced concrete structure house

3.0–4.0

3.5 –4.5

4.2–5.0

4

Ancient buildings and monuments

0.1–0.3

0.2–0.4

0.3–0.5

5

Hydraulic tunnel

7–15

6

Traffic tunnel

10–20

7

Mine tunnel

15 –30

8

Central control room equipment for hydropower stations and power plants

0.5

9

Freshly poured mass concrete d: Age: primary–3d Age: 3–7d Age: 7–28d

2.0–3.0 3.0–7.0 7.0–12

Note 1. The frequency listed in the table is the main vibration frequency, which refers to the frequency of the wave corresponding to the maximum amplitude 2. The frequency range can be selected based on similar projects or on-site measured waveforms. The following data can also be referred to when selecting the frequency: chamber blasting < 20 Hz; deep hole blasting 10 Hz ~ 60 Hz; shallow hole blasting 40 Hz ~ 100 Hz (a) When selecting the building safety allowable vibration speed, factors such as the importance of the building, the quality of the building, the degree of newness, the natural vibration frequency, and the foundation conditions should be considered comprehensively (b) The safety permissible vibration speed of key protected ancient buildings and historical sites at or above the provincial level (including the provincial level) should be selected through expert evaluation and reported to the corresponding cultural relics management department for approval (c) When selecting the safe allowable vibration speed of tunnels and roadways, factors such as the importance of the structure, the condition of the surrounding rock, the size of the section, the size of the depth, the direction of the blasting source, and the frequency of seismic vibration should be comprehensively considered (d) The safe permissible vibration speed of non-water-retaining newly poured mass concrete can be selected according to the upper limit given in this table

References

113

Table 6.9 Blasting vibration speed control standards for subway tunnels passing through key buildings Number

Building categories

Safe allowable vibration speed (cm/s) < 10 Hz

10–50 Hz

50–100 Hz

1

Adobe houses, rubble houses

0.3–0.5

0.5–0.7

0.7–1.0

2

Brick and wood structure Non-seismic masonry building

1.0–1.2

1.2–1.5

1.5–2.0

3

Brick-concrete structure before 2002

1.2–1.5

1.5–1.8

1.8–2.0

4

Brick-concrete structure after 2002

1.5–1.8

1.8–2.0

2.0–2.5

5

Steel concrete structure before the 90 s

1.8–2.0

2.0–2.5

2.5–3.0

6

Steel–concrete structure from 1990 to 2002

2.0–2.5

2.5–3.0

3.0–3.5

7

Steel concrete structure after 2002

3.0–3.5

3.5–4.0

4.0–4.5

8

General ancient building

0.3–0.5

0.5–0.7

0.7–1.0

9

Cultural relics and ancient buildings

0.1–0.3

0.3–0.4

0.4–0.5

Note 1. The listed frequency is the main vibration frequency, which refers to the frequency of the wave corresponding to the maximum amplitude; 2. When selecting the allowable vibration speed for building safety, factors such as the importance of the building, the quality of the building, the degree of newness, the natural vibration frequency, and the foundation conditions should be considered comprehensively; 3. The safety permissible vibration speed of the key protected ancient buildings and historical sites at or above the provincial level (including the provincial level) should be selected by expert argumentation and reported to the corresponding cultural relics management department for approval; 4. The vibration speed control standard of the site with the possibility of liquefaction must be selected through expert argumentation; 5. 60% early warning and 80% warning of the data in the table

References 1. Dan M, Zang X, Yu G et al (2012) Chin J Rock Mech Eng 31(6):1–6 2. Attewell PB, Yeates J, Selby AR (1986) Soil movements induced by tunneling and the effects on pipelines and structures. Blackie and Son, London 3. Zhang D (2005) Environmental safety risk management in urban subway construction. China Civ Eng J 38(S.):5–9 4. Luo J, Zhang D, Wang M et al (2007) Safety risk management of adjacent buildings in subway construction. Rock Soil Mech 28(7):83–87 5. Zhang C, Luo F (2007) Environmental safety risk management system in subway construction. Urban Rapid Transit 20(4):63–65 6. Hou Y, Zhang D, Zhang B (2011) Urban tunnel construction risk management system. J Underground Space Eng 7(5):989–995 7. Xie N, He H (2007) Discussion on cyclic dynamic risk management system in engineering construction. Chin J Underground Space Eng 3(8):1533–1536 8. He Z (1981) Fuzzy mathematics and its application. Tianjin Science and Technology Press, Tianjin 9. Zhao X, Zhao J (1998) Fuzzy thinking and generalized design. China Machine Press, Beijing 10. Chen S (1993) Fuzzy optimal classification theory model and its application in surrounding rock stability classification and site soil classification evaluation. J Hydraul Eng 12:26–36

Chapter 7

Law of Ground Movement in Foundation Pit Construction of Adjacent Tunnel Buildings

In the process of foundation pit excavation, different degree of soil stress release is inevitably caused, which leads to the displacement of supporting structure system and ground around the pit, resulting in additional stress and additional deformation to the adjacent tunnel. Excessive deformation will lead to cracking and leakage of the tunnel, which will affect the structural safety and normal operation of the tunnel. Therefore, it is necessary to study the influence law of foundation pit excavation on the existing tunnel, evaluate the stability of foundation pit and tunnel, and study the related technical measures to ensure the safety of tunnel and building foundation pit. This chapter for shallow buried tunnel adjacent formation deformation caused by the construction of foundation pit construction, the statistical analysis of building foundation pit excavation at home and abroad Law of influence on adjacent tunnel and Qingdao typical geological conditions of strata movement rule, for subsequent tunnel safety impact assessment, building foundation pit construction technology and construction technology and monitoring index, method and technology lay the foundation for improvement.

7.1 Statistical Analysis of the Influence of Foundation Pit Excavation on Adjacent Tunnels The surrounding environment of urban engineering construction is becoming more and more complex. In the design and construction of foundation pit for structures such as subway tunnel, the requirement of deformation control of foundation pit is becoming more and more strict. The method of strength control design is gradually replaced by the method of deformation control design. The deformation analysis of foundation pit becomes an extremely important part in the design of foundation pit engineering. According to the “Foundation Pit Engineering Manual” on the “general allowable deformation amount” of subway tunnel: the maximum displacement of the structure should not exceed 20 mm, the tunnel deformation curvature radius © China Architecture Publishing & Media Co., Ltd. 2022 D. Meng et al., Prediction and Control of Interaction Between Ground Building and Tunnel Construction Process, https://doi.org/10.1007/978-981-19-3474-2_7

115

116

7 Law of Ground Movement in Foundation Pit Construction …

should not be less than 5000 m, the relative bending should not exceed 1/2500. If the additional deformation caused is too large, the tunnel structure will be damaged, serious will lead to subway tunnel cracking, groundwater seepage, and so on, thus affecting the normal operation of the tunnel. The research on the deformation of adjacent tunnels caused by foundation pit excavation mainly includes field monitoring analysis, theoretical analysis and numerical simulation analysis. In this section, foundation pit engineering cases of relevant adjacent existing tunnels (Table 7.1) are collected and counted, and the influence of foundation pit excavation on adjacent tunnels is discussed from the perspectives of vertical displacement, horizontal displacement and tunnel convergence, etc. The research results obtained can provide reference for the design and construction of similar foundation pit projects. Further statistical analysis of the 20 engineering cases in Table 7.1 shows that: (1)

The horizontal displacement caused by the excavation of the foundation pit and the horizontal distance between the foundation pit and the tunnel presents approximately a number attenuation relationship (Fig. 7.1); The vertical displacement of the adjacent tunnel caused by the excavation of the foundation pit has an exponential relationship with the horizontal distance between the foundation pit and the tunnel (Fig. 7.2).

In guarantee tunnel in rock and soil layer physical and mechanical properties of similar cases, can be concluded from the Fig. 7.1, foundation pit with the size of the horizontal distance of the tunnel for greater influence on the displacement of the tunnel, and the horizontal displacement produced by tunnel excavation to the horizontal distance of the tunnel is roughly power function attenuation relationship, the closer the horizontal distance between them, the tunnel horizontal displacement is larger. When the horizontal distance between the tunnel and the foundation pit is less than 5 m, the horizontal displacement of the tunnel is greatly affected, and the horizontal displacement is 8–14 mm. When the horizontal distance between the tunnel and the foundation pit is 5–13 m, the horizontal displacement of the tunnel is 4–7 mm. When the horizontal distance between the tunnel and the foundation pit is greater than 13 m, the horizontal displacement of the tunnel is less than 4 mm. The horizontal distance between the foundation pit and the tunnel also has a great influence on the vertical displacement of the tunnel. According to the statistics of the measured data, the vertical displacement generated by the tunnel is roughly exponentially related to the horizontal distance between the foundation pit and the tunnel. As shown in Fig. 7.2, an engineering case where the horizontal distance between the tunnel and the foundation pit is less than 5 m shows that the additional vertical displacement generated by the tunnel is relatively large, about 4.2–9.5 mm. When the horizontal distance between the tunnel and the foundation pit is greater than 5 m, the vertical displacement of the tunnel decreases gradually. It is important to note that the listed in Table 7.1 of the first three cases are in above tunnel excavation of foundation pit, at this point, the horizontal displacement is small tunnel, tunnel rise significantly, floating tunnel vault is located at the pit bottom, is the cause of

1

The length × width × depth of the foundation pit of an underground passageway is 30 m × 13 m × 8 m, and the main body adopts box-shaped concrete structure

Number Foundation pit profile

The minimum clear distance of the tunnel roof under the foundation pit is 7.9 m

The tunnel location Silty clay

Tunnel soil

Table 7.1 Twenty relevant engineering cases at home and abroad

Enclosure structure using four rows Φ800@600 high pressure jet pile, enclosure structure at the entrance of the passage adopts two rows of Φ800@600 × 600 high-pressure jet grouting piles. The enclosing pile adopts Φ800@1000 bored cast-in-place pile, and the supporting system is concrete-supported steel enclosing purlin and steel bracing

Building envelope Adopt Φ600@1500 bored pile The soil in the pit was strengthened by Φ 800@600 high pressure jet grouting pile

Reinforce the situation Considering the effect of time and space, the excavation is divided into small open excavation

Earth cutting

(continued)

Excavation of the foundation pit can cause the tunnel to float up to a maximum of 1.9 mm, which has little effect on the horizontal displacement, and the horizontal convergence is 5.9 mm

Tunnel deformation

7.1 Statistical Analysis of the Influence of Foundation … 117

2

The depth of foundation pit excavation is 18.4 m at Chegongmiao junction station of a subway, and 8.1 m at Xifeng Road

Number Foundation pit profile

Table 7.1 (continued) Tunnel soil

The minimum net Gravel clay distance of tunnel roof in the foundation pit is 3 m, and the distance between the upper line and the left uplift pile is 0.7 m

The tunnel location The enclosure is reinforced by underground diaphragm walls with steel braces of 5 m longitudinal spacing

Building envelope There are two rows of anti-floating piles under the bottom plate of the air duct. The diameter of the bored cast-in-place piles is 1000 mm, the embedded depth is 12 m, and the characteristic value of the single pile’s anti-pulling force is 520kN. Adopt Φ600@450MJS rotary jet pile with adjustable pressure to reinforce the whole hall

Reinforce the situation

Tunnel deformation

(continued)

Firstly, the roof Overall uplift is structure of the 7.0 mm station is constructed, and then the foundation pit of the air duct is excavated, so that the concrete support on the top of the foundation pit of the air duct and the roof of the station form a horizontal force transmission system. The excavation of the station foundation pit is carried out in layers and sections

Earth cutting

118 7 Law of Ground Movement in Foundation Pit Construction …

The minimum clear distance of the tunnel roof under the foundation pit is 5.4 m

An east–west passageway crosses a subway project, and the depth of the foundation pit is about 11 m

The deep foundation pit of a square is 17.5 m deep

3

4

Building envelope

The foundation pit retaining structure adopts dense single row of bored cast-in-place piles and horizontal steel bracing, which are respectively arranged on the northwest side of the foundation pit, adjacent to the foundation pit section of the subway tunnel. The inner supporting system consists of 609 × 20 diameter steel pipe, 400 × 400H section steel and several steel plates

Clay, silty clay The borehole cast-in-place pile of Φ800@1000 is used as the enclosure structure, and the vertical pit is supported by concrete and steel. The sound-proof wall and anti-pulling pile are designed on both sides of the tunnel, and the borehole cast-in-place pile is also used

Tunnel soil

The minimum Medium and horizontal coarse sand distance between the foundation pit and the outer boundary of the subway tunnel is 7–10 m, and the top of the tunnel is 10 m higher than the bottom

The tunnel location

Number Foundation pit profile

Table 7.1 (continued) Earth cutting

According to the space-time effect principle, layered excavation. First, the middle earthwork is excavated to form the support, then the two sides of the earthwork are excavated at the same time, and finally the diaphragm wall is constructed

At the bottom of Layered and the pit, the depth zoned excavation, of reinforcement strip excavation is the bottom elevation of the tunnel, and a reinforcement area with a height of 5 m is extended to both sides of the foundation pit

Reinforce the situation

(continued)

The maximum settlement value of the tunnel reached 4 mm. Maximum horizontal displacement is 7 mm

The maximum vertical uplift of the tunnel is 6.5 mm

Tunnel deformation

7.1 Statistical Analysis of the Influence of Foundation … 119

The tunnel Silt with silty segment is about clay 12.78–13.50 m away from the horizontal side of the foundation pit, and the top of the tunnel is 8.3 m above the bottom

The plane of a foundation pit is rectangular. The excavation area of the foundation pit is about 3890m2 , and the excavation depth is 17.00 m

5

Tunnel soil

The tunnel location

Number Foundation pit profile

Table 7.1 (continued)

The retaining structure of the foundation pit is as follows: 1000 mm thick underground diaphragm wall is used in the south, Φ1050@1250 underwater C30 bored pile is used in the other three sides, and single row cement mixing pile is used in the water stop curtain, the net distance between mixing pile and cast-in pile is 150 mm, close to the underground continuous wall, and three reinforced concrete horizontal supports are se

Building envelope

Reinforce the situation The foundation pit is layered and excavated to the design elevation, and concrete enclosing purlins is poured

Earth cutting

(continued)

Left settlement 2.14 mm, horizontal displacement 5.76 mm

Tunnel deformation

120 7 Law of Ground Movement in Foundation Pit Construction …

The north shaft of Silty clay, silty the station is only clay 15 m away from Line 2, and the top of the tunnel is 12 m above the bottom

The excavation depth of a station foundation pit is 23.35 m, and the depth of the end shaft is 25.09 m

6

Tunnel soil

The tunnel location

Number Foundation pit profile

Table 7.1 (continued)

Underground diaphragm wall and SMW mixing pile are used in the outer row of 3 m envelope structure. After the construction of the diaphragm wall is completed, the soil in the area of 3 m outside and inside the pit is reinforced by rotary jet grouting pile for the second time. The supporting structure is constructed by reverse method, with a total of seven supports, among which the first one is surrounded by reinforced concrete support with a section size of 800 mm × 800 mm, and the other six are supported by steel pipes

Building envelope In the 3 m area outside the pit, the soil is reinforced with rotary jet grouting pile, while in the pit, the high pressure rotary jet grouting pile is used to reinforce the soil, and the depth reaches 3 m below the pit bottom. Add layers of reinforcement at floor position

Reinforce the situation Block construction: the head groove wall is set at the connection between the well and the main body of the parking lot, and the main body of the station is constructed after the construction of the end well is completed

Earth cutting

(continued)

The upstream settlement of the tunnel is 1.3 mm and the horizontal displacement is 3.2 mm

Tunnel deformation

7.1 Statistical Analysis of the Influence of Foundation … 121

The upper line of Silty clay, silty the tunnel is clay 10.4–13.5 m from the outside of the continuous wall of the foundation pit, and the top of the tunnel is 8 m above the bottom

The area of a foundation pit is about 10228 m, and the excavation depth is 15.6m2

7

Tunnel soil

The tunnel location

Number Foundation pit profile

Table 7.1 (continued)

Underground diaphragm wall is used for the retaining structure. Cement mixing piles are set on both sides of the underground diaphragm wall adjacent to the subway as the trench wall reinforcement. The foundation pit in I district is supported by underground diaphragm wall + three cross orthogonal concrete. The foundation pit in II area adopts underground continuous wall + the first concrete brace + three steel brace. A Φ850@600 triaxial cement mixing pile is set on the side adjacent to the subway, and a double row of triaxial cement mixing piles are set outside the foundation pit on one side of the subway for reinforcement

Building envelope The reinforcement depth of the substation zone is about 7.3 m from the second channel to the base, and the width is about 10–15 m. The reinforcement depth of II zone is about 5.0 m below the base from the second channel

Reinforce the situation Excavate earthwork far away from the subway side to form a temporary support in the middle, and adopt the method of “spacing and strip extraction” in the adjacent soil. The II area adopts the principle of stratification and stratification

Earth cutting

(continued)

Near side subway tunnel: horizontal deformation is 13.13 mm, vertical deformation is 2.66 mm; Far side subway tunnel: horizontal deformation of 1.97 mm, vertical deformation of 1.34 mm

Tunnel deformation

122 7 Law of Ground Movement in Foundation Pit Construction …

8

The average excavation depth of the second phase foundation pit project of a subway line 9 is 10.9 m

Number Foundation pit profile

Table 7.1 (continued) Tunnel soil

The nearest Mucky clay distance between the tunnel and the foundation pit is about 4.8 m

The tunnel location The retaining structure adopts 800 mm thick underground continuous wall, plus two horizontal supports, the first is reinforced concrete support, the second is steel pipe support. First, double rows of rotary jet grouting piles with 600 mm diameter and 450 mm spacing are constructed on the east continuous wall, and then the row of piles near the tunnel is constructed, and the sequential hole leaping construction is adopted every two hits one

Building envelope Deep well point dewatering, deep mixing piles are used to reinforce around the foundation pit, with a depth of 5 m under the foundation pit and a width of 8m

Reinforce the situation Layered, block, symmetrical and limited time. After the strength of the first support reaches 70%, the foundation pit is divided into 6 symmetrical pieces, first supported and then excavated, and excavated in layers and zones

Earth cutting

(continued)

The final settlement is 4.2 mm and the maximum horizontal displacement is 8 mm

Tunnel deformation

7.1 Statistical Analysis of the Influence of Foundation … 123

The horizontal Mucky clay distance between the tunnel and the foundation pit is 11.5 m, and the top of the tunnel is 4.8 m below the bottom

The depth of a foundation pit is 6.45 m and 4.95 m

9

Tunnel soil

The tunnel location

Number Foundation pit profile

Table 7.1 (continued)

The foundation pit retaining structure adopts borehole pouring pile Φ400@1000 with a depth of 13 m. The surrounding pouring pile adopts 4 rows of 4700 biaxial mixing piles as water curtain, and the buried depth of pile bottom is 13 m. One side of the subway is equipped with an oblique cast steel brace, which is supported in the middle of the subway. The soil layer formed by the first excavation is set with a bottom plate. The subway side of the foundation pit is set with a mixing pile pier type reinforcement

Building envelope Four rows of Φ700 mixing piles are used as water stopping curtains for the surrounding excavation. The depth of burial is 13 m. Mixing piles and piers are used for reinforcement near the foundation pit

Reinforce the situation According to the principle of space-time effect, the excavation is carried out in blocks, layers and symmetrically. Do layered, zoned, block, symmetrical, balanced, limited time” excavation support

Earth cutting

(continued)

The measured displacement of the tunnel is 5.3 mm, the horizontal displacement is 5.92 mm, and the vertical displacement is 5.71 mm

Tunnel deformation

124 7 Law of Ground Movement in Foundation Pit Construction …

10

The excavation area of a foundation pit is 8230m2 and the excavation depth is 20.72 m

Number Foundation pit profile

Table 7.1 (continued) Tunnel soil

The nearest Silty clay, silty horizontal clay distance between the tunnel and the north area of the foundation pit is 5.4 m, the buried depth of the tunnel is 8.5 m, and the top of the tunnel is about 9.5 m above the bottom

The tunnel location The excavation is protected by an integrated diaphragm wall with a thickness of 1000 mm and a depth of 36 m, 39.5 m and 41 m respectively. There are 3 reinforced concrete horizontal supports in the pit. The exterior of the underground continuous wall is reinforced by the sandwich of triaxial mixing piles

Building envelope North foundation pit reinforcement, from 7 m below the bottom to the ground using full reinforcement, cement infiltration amount is not less than 20%, the unconfined strength of the strengthened soil is not less than 1.5 MPa

Reinforce the situation Excavate to the bottom of the pit, and construct each layer of underground structure successively from bottom to top. The foundation pit excavation follows the principles of “stratification, partition, retaining soil and retaining wall, symmetry, time limit and excavation support”. The space-time effect principle is used to reduce the time without support

Earth cutting

(continued)

The accumulative maximum settlement value is 16.67 mm

Tunnel deformation

7.1 Statistical Analysis of the Influence of Foundation … 125

11

The tower area and one side of Xiangyang North Road were excavated to a depth of 11 m, and the surrounding podium was excavated to a depth of nearly 9m

Number Foundation pit profile

Table 7.1 (continued) Tunnel soil

The nearest Grey muddy horizontal clay, clay distance between the tunnel and the foundation pit is 3.8 m. The top elevation of the tunnel is 2 m below the bottom of the pit

The tunnel location The enclosure structure is an underground continuous wall with a width of 600–800 mm and a depth of 18–20 m. The north side adopts bored cast-in-place piles (Φ = 1000 mm, L = 18 m), and the two rows of mixing piles behind the piles stop water. Two concrete support, the absolute elevation of − 2.4 m, − 7.0 m respectively. Partial use of double limb steel tube support

Building envelope 1. Full reinforcement of cement mixing pile with a depth of 5 m; 2. The width of subway tunnel side reinforcement is up to 10 m, the cement content is 15%, and the above base is 8%; 3. Compact grouting was carried out at the gap between the deep mixing pile reinforcement area and the ground wall

Reinforce the situation The basin type excavation in the middle and the surrounding area should be supported by ‘layered, zoned, partitioned, symmetrical balance and limited time’ excavation. The width of the soil left in the side excavation of the subway is no less than 4 times the depth of the layer, and the excavation support of a single block of soil is controlled within 16–24 h

Earth cutting

(continued)

The cumulative settlement reaches 9 mm corresponding horizontal displacement: 9.5 mm for the upward line, 8 mm for the downward line; The maximum stretching rate of tunnel segments is up to 0.3 mm/d in the direction of excavation unloading

Tunnel deformation

126 7 Law of Ground Movement in Foundation Pit Construction …

The upward Mucky clay tunnel is 22–26 m away from the foundation pit, and the downward tunnel is 7–11 m away from the foundation pit. The top elevation of the downstream line of the tunnel is 5.1 m above the bottom of the pit

The depth of the foundation pit of a square project is 14.4 m

12

Tunnel soil

The tunnel location

Number Foundation pit profile

Table 7.1 (continued)

An underground diaphragm wall is adopted. On the side of Nanjing Road, the diaphragm wall is 33 m deep and 1 m thick, while the rest part is 31 m deep and 0.8 m thick. There are three internal supports, the absolute elevation of which is 1.95 m, − 7 m and − 11.5 m respectively

Building envelope On the south side of the foundation pit (near the subway side), a rotary-jet grouting pile with a width of 6.2 m and a reinforcement depth of 5 m below the pit bottom is adopted for reinforcement. The mixing pile above the pit bottom is reinforced with 13% cement slurry and 8% water and mud

Reinforce the situation In basin excavation, according to the principle of symmetry and balance, that is, after the middle earthwork is excavated to form a support, the earthwork on both sides should be excavated and connected to the underground wall at the same time within a specified time

Earth cutting

(continued)

Settlement: up line 8 mm, down line 10 mm; Horizontal displacement (movement in pit): up line mm, down line 10 mm. The tunnel converges in the shape of a transverse duck egg, with a horizontal elongation of 7.3 mm and a vertical shortening of 21.2 mm

Tunnel deformation

7.1 Statistical Analysis of the Influence of Foundation … 127

The middle Silty silty clay partition wall is only 2.8–5 m away from the subway downward tunnel, and the tunnel top elevation is 0.7 m above the bottom of the north pit

The foundation pit of a square (north pit) is 15.1–16 m deep

13

Tunnel soil

The tunnel location

Number Foundation pit profile

Table 7.1 (continued)

The north pit adopts an underground continuous wall with a thickness of 800 mm, a depth of 25.2 m, and four reinforced concrete supports, whose absolute elevations are + 1.8 m, − 1.3 m, − 4.7 m and − 8.5 m respectively. Outside the diaphragm wall, cast-in-place piles with a diameter of 850 mm and a length of 25 m are used。

Building envelope Beikeng high-pressure rotary jet reinforcement, reinforcement scope: from 8 m above the bottom of the pit near the middle partition wall to 5 m below the bottom of the ladder reinforcement; Two grilles on both sides of the tunnel are 2.2 m and 1.5 m thick

Reinforce the situation According to the principle of “east to west, north first, then south”, the excavation was completed in three times from east to west. The earthwork shall be overlapped and excavated in stages according to “3 areas and 5 blocks”

Earth cutting

(continued)

Settlement: downline 5 mm; The upward line is 7.5 mm. Horizontal displacement: 13 mm down line, 10 mm up line. The tunnel converges in a transverse duck-egg shape, and the maximum horizontal elongation is 22.5 mm

Tunnel deformation

128 7 Law of Ground Movement in Foundation Pit Construction …

The north of the foundation pit (along Huaihai Road) is adjacent to the subway, with the nearest 3.8 m and the farthest 8 m

14

The deep foundation pit of a square covers an area of about 5800m2 , the excavation depth of the main building is 14 m, and the podium building is 12.6 m

The tunnel location

Number Foundation pit profile

Table 7.1 (continued)

In silty clay

Tunnel soil The underground continuous wall with the thickness of 800 mm is supported by five reinforced concrete lines with the elevations of − 0.6 m, − 3.5 m, − 6.4 m, 9.5 m and − 13.1 m respectively. On the plane, the foundation pit is supported by side frame, and the diagonal brace is the main brace

Building envelope Deep mixing piles are used for reinforcement around the foundation pit, and the reinforcement width is 8 m when the depth reaches 5 m below the foundation pit. Deep well point precipitation is adopted

Reinforce the situation The principle of excavation is layered and zoned. After the first support reaches 70% of the strength, the foundation pit is excavated symmetrically in 6 small pieces on the plane. The following analogy

Earth cutting

(continued)

The maximum settlement is 6.07 mm (when the fourth support is used), and the settlement of the bottom plate becomes 4.2 m after pouring. The maximum horizontal displacement is 8 mm

Tunnel deformation

7.1 Statistical Analysis of the Influence of Foundation … 129

15

The excavation depth of the foundation pit of a People’s Park Station of Metro Line 2 is 22.12 m

Number Foundation pit profile

Table 7.1 (continued) Tunnel soil

The nearest Silty clay, silty distance between clay, silty clay Line 1 and the foundation pit is 10.7 m, and the elevation of the tunnel top is about 16.4 m from the bottom

The tunnel location Adopt two light and one dark and half reverse construction. Subterranean diaphragm wall is 800 mm thick and 40 m deep. The elevation of the six Angle braces is − 0.52 m, − 4.85 m, − 8.74 m, − 11.47 m, − 17.07 m and − 19.5 m respectively

Building envelope

Reinforce the situation According to the space-time effect principle, the excavation is divided into six blocks

Earth cutting

(continued)

The maximum settlement is 10 mm and the maximum horizontal displacement of the diaphragm wall is 60 mm

Tunnel deformation

130 7 Law of Ground Movement in Foundation Pit Construction …

16

The excavation depth of a foundation pit is 6.45 m, 4.95 m and 3.5 m respectively

Number Foundation pit profile

Table 7.1 (continued) Tunnel soil

The interval Silty clay, silty tunnel of Line 8 is clay 11.5 m away from the edge of the foundation pit and the buried depth of the tunnel top is 10 m

The tunnel location The underground foundation pit adopts Φ700@1000 bored cast-in-place pile, the buried depth of pile bottom is 13 m, one horizontal support, and its elevation is − 2 m(relative to 0.0)

Building envelope

(continued)

According to the The tunnel has a space-time effect 5.3 mm principle, the displacement excavation is carried out in layers and blocks

Φ700SMW mixing pile in 4 rows is used as water stop curtain, and the buried depth of pile bottom is 13 m. The subway foundation pit side is equipped with skirt-type integral reinforcement

Tunnel deformation

Earth cutting

Reinforce the situation

7.1 Statistical Analysis of the Influence of Foundation … 131

17

The excavation depth of a transportation hub center is 6.72 m

Number Foundation pit profile

Table 7.1 (continued)

20 m away from the axis of rail transit station

The tunnel location

Tunnel soil Subterranean continuous walls with a thickness of 800 mm are used, with structural beams instead of temporary support (a horizontal support system)

Building envelope

Reinforce the situation

Earth cutting

(continued)

Station structure settlement 5.3 mm; Track structure settlement − 1.3 mm

Tunnel deformation

132 7 Law of Ground Movement in Foundation Pit Construction …

The upper line of Line 4 is 9.89 m away from the outer wall of the foundation pit. The thickness of tunnel roof soil is 11 m

18

The total area of a foundation pit is about 7548 m. The excavation depth of the tower area is 10.25m2 . Underground garage 9.45 m.

The tunnel location

Number Foundation pit profile

Table 7.1 (continued)

Silty clay

Tunnel soil The tower part adopts 800 mm thick underground continuous wall, and the underground garage part adopts 600 mm thick underground continuous wall. Two reinforced concrete horizontal support, the elevation of − 2.15 m, − 6.9 m

Building envelope In the side pit near the subway, Φ560@450 cement mixing pile is used for reinforcement, with a width of 6.05 m and a depth of 6.5 m from the bottom of the second support to the bottom of the pit. Metro pit side Φ800@1000 high pressure jet grouting pile is used between the inner reinforcement and the groove wall, and the other positions are compressed grouting

Reinforce the situation In accordance with the requirements of “layered blocks, symmetrical blocks and limited time”, the soil is excavated by drawing strips at intervals, and the length of each block is no more than 20 m during block excavation

Earth cutting

(continued)

Maximum lateral displacement is 1.9 mm and vertical displacement is 8.4 mm(finite element results)

Tunnel deformation

7.1 Statistical Analysis of the Influence of Foundation … 133

The tunnel is 3 m Silty clay away from the foundation pit, and the buried depth is 11 m. The roof of the tunnel is about 4.7 m above the bottom

The excavation area of a foundation pit is 16429m2 , and the bottom elevation of the south pit near the subway side is − 15.725 m

19

Tunnel soil

The tunnel location

Number Foundation pit profile

Table 7.1 (continued)

1 m thick underground diaphragm wall, depth 32.45 m, four grid support. The first line is 1000 mm × 800 mm reinforced concrete support, and the second, third and fourth lines are 609 mm × 16 mm double steel pipe support. The elevations of the support are − 1.75 m, 6.45 m, − 9.95 m and − 13.025 m respectively

Building envelope At different elevations of the bottom of the pit, the triple-pipe grouting method of high pressure jet grouting pile is adopted for layered reinforcement, with thickness of 3.0 m and 2.6 m respectively. The diameter of the grouting body is not less than 1.2 m, and the pile lap is more than 400 mm

Reinforce the situation

Earth cutting

(continued)

The tunnel produced a settlement of 8 mm

Tunnel deformation

134 7 Law of Ground Movement in Foundation Pit Construction …

The foundation Silty clay, clay pit is about 7 m from the tunnel nearest, and the bottom of the foundation pit is 4 m lower than the roof of the tunnel

The excavation depth of a foundation pit is 11.5 m

20

Tunnel soil

The tunnel location

Number Foundation pit profile

Table 7.1 (continued)

The underground wall adjacent to the subway is 1 m thick and 23 m deep, and the other three sides are 0.8 m thick and 23 m deep

Building envelope The deep stirring pile was combined with high pressure rotary jet injection for reinforcement, and the bottom of the surrounding pit was reinforced by 5 m thick stirring piles with a width of 7.2 m. The reinforcement width near the subway side is 10 m, and the width is increased by 2.8 m High pressure rotary jet reinforcement; Above the bottom of the pit, skirt suction strips are used to reinforce to the ground

Reinforce the situation Layered, block, symmetrical, balanced, time-limited excavation and pouring cushion, basin excavation of the middle cushion, and then to the two sides of the excavation

Earth cutting

The maximum horizontal displacement generated by the tunnel is 4 mm

Tunnel deformation

7.1 Statistical Analysis of the Influence of Foundation … 135

136

7 Law of Ground Movement in Foundation Pit Construction …

Fig. 7.1 Relationship curve of the influence of horizontal distance between foundation pit and tunnel on horizontal displacement of tunnel

Fig. 7.2 Influence curve of horizontal distance between foundation pit and tunnel on vertical displacement of tunnel

excavation unloading, soil pit uplift, drive the lower soil moving up, causing the tunnel to rise. The horizontal displacement of the tunnel caused by the excavation of the foundation pit has no significant rule with the height difference between the bottom of the foundation pit and the vault of the tunnel, showing a large dispersion (Fig. 7.3). The vertical displacement of the tunnel caused by the excavation of the foundation pit is linearly correlated with the height difference between the bottom of the foundation pit and the vault of the tunnel (Fig. 7.4). The space-time effect of reinforcement and excavation in the pit will affect the tunnel deformation, and the reasonable reinforcement and space-time effect excavation in the pit can effectively control the tunnel deformation.

7.1 Statistical Analysis of the Influence of Foundation …

137

Fig. 7.3 Influence of height difference between tunnel vault and foundation pit on horizontal displacement of tunnel

Fig. 7.4 Influence of height difference between vault and foundation pit on vertical displacement of tunnel

In the above statistical cases, the adjacent existing tunnel foundation pits are basically excavated by basin type excavation, and the excavation is carried out according to the “space-time effect principle” of the excavation principle of “layered, block, symmetrical, balanced and limited time”. Generally, the soil with low protection level in the middle of the foundation pit is first excavated, and the width of the soil on the side of the adjacent subway tunnel is reserved after the support is formed in time. Finally, this part of the soil is excavated and supported while excavating, and the construction time of each block of excavated soil support is controlled. (2)

Taking into account the deformation datum of tunnel structure in different directions to formulate reasonable precipitation measures is beneficial to control tunnel deformation.

138

7 Law of Ground Movement in Foundation Pit Construction …

7.2 Strata Movement Law Under Typical Geological Conditions in Qingdao Qingdao region has a special rock hard “under” on soft soil binary structure geological conditions, the surface of the quaternary soil layer is not development, some areas are rich in groundwater, some poor area hydrogeology, underlying bedrock of yanshan period granite, granite weathering, breeze in the tunnel through the occurrence in the joints of borehole, and generally contains 2–3 joints, and the lamprophyre intrusive. In view of the above characteristics and combined with the field measured data, the surface settlement curves caused by underground excavation in Qingdao are summarized into the following five types of curves: slow normal distribution curve or settlement pit, steep normal distribution curve, skewed sub-settlement curve, funnel collapse pit and step settlement curve. In this section, a Poisson distribution prediction model for surface subsidence considering joint trace length, joint spacing and joint dip Angle is established according to the typical geological conditions of soil-rock duality structure with “soft upper and hard lower”. The calculated results of the model are in good agreement with the actual monitoring results, which can be used as a guide for practical design, construction and field prediction. It is assumed that there are inclined joints with unequal joint spacing and track length, and the joint track width is A, the joint track length is B, and the joint track length is α. If, after the rock block A1 is excavated from the lowest level, the inclined joints in the rock strata cause unequal opportunities for A2 and B2 to fall. D represents the horizontal distance between the center of the rock block and the excavation center line. Through geometric deduction, the falling probabilities of A2 and B2 are respectively: ⎧ 1 ⎪ ⎨ pa2 = (1 + λ cos α) = p1 2 ⎪ ⎩ p = 1 (1 − λ cos α) = p 2 b2 2

(7.1)

in the formula λ is the track length to spacing ratio, λ = ab . It can be deduced that the falling probability of the k rock block in the NTH layer affected by excavation is: ( )n 1 P(X = k) = Cnk (1 + λ cos α)n−k (1 − λ cos α)k 2

(7.2)

⌈ H ⏋ in the formula n = b sin , H is the tunnel buried depth (m), k ∈ [0, n]. α Considering the number of rock strata n ≥ 10 in practical application, the Poisson distribution function can be used to replace the binomial distribution, namely:

7.3 Conclusion

139

P(X = k) =

m k −m e k!

(7.3)

in the formula m is the poisson distribution parameters. Then, in the rock mass with a depth of H, joint dip Angle of α, average joint spacing of A, and joint trace length of B, the surface subsidence caused by excavation unit block can be expressed as ωck = c × b sin α × P(X = k)

(7.4)

in the formula c is the subsidence coefficient related to rock properties. It is necessary to assign the value according to the actual situation, and through the corresponding inversion fitting calculation on the data provided by the relevant projects in Qingdao, it is considered that the value in Qingdao area is generally 0.05–0.08.

7.3 Conclusion Statistics in this chapter 20 A building foundation pit excavation of adjacent tunnel at home and abroad, analyzed the foundation pit excavation adjacent to the horizontal displacement of the tunnel and foundation pit to the horizontal distance of the tunnel is power function attenuation relations, caused by excavation adjacent to the vertical displacement of the tunnel and the excavation to the exponential relationship between the level distance of the tunnel, the excavation adjacent tunnel construction of foundation pit construction ground movement regularity of adjacent tunnel. The horizontal displacement has a large discrete relationship with the height difference between the foundation pit bottom and the tunnel vault, the vertical displacement caused by the excavation of the foundation pit has a linear correlation with the height difference between the foundation pit bottom and the tunnel vault, and the space-time effect of the reinforcement and excavation in the pit will have an influence on the deformation of the adjacent tunnel. At the same time, the rock strata movement law of underground engineering excavation under the typical geological conditions of soil and rock binary structure is systematically analyzed. The stochastic discrete model of surface subsidence with joint inclination is established, which integrates geological model and mathematical model, and the Poisson distribution prediction model of surface subsidence considering joint trace length, joint spacing and joint inclination is deduced.

Chapter 8

Key Technologies for Foundation Pit Construction of Adjacent Tunnel Buildings

On the basis of the previous chapter, this chapter puts forward adjacent existing tunnel on the impact of building foundation pit construction on the tunnel safety evaluation system, evaluation index and evaluation method, gives the adjacent existing shallow buried tunnel construction of foundation pit, construction technology and construction technology in the process of the construction and the need for monitoring index and monitoring methods and technical measures.

8.1 Main Research Steps and Content The excavation of urban building foundation pit breaks the original stress balance state of soil mass, causes stress redistribution and soil layer deformation, which is transferred to the nearby shallow buried tunnel, causing tunnel deformation and endangering tunnel safety. This chapter studies this problem. According to the foundation pit excavation construction procedure, the technical route is shown in Fig. 8.1. Detailed description of each step is as follows: The first step is to research and develop the foundation pit construction technology and construction technology of adjacent shallow buried tunnels. (1) (2)

The evolution law of deformation of adjacent tunnels caused by rock strata movement due to foundation pit excavation was studied. Research and develop the foundation pit construction technology and construction technology of adjacent shallow buried tunnels to reduce the impact of foundation pit excavation on adjacent tunnels.

The second step is the evaluation index and method of the influence of foundation pit construction on tunnel safety. (1)

Find out the influence factors of engineering construction on the tunnel, and carry on the overall evaluation;

© China Architecture Publishing & Media Co., Ltd. 2022 D. Meng et al., Prediction and Control of Interaction Between Ground Building and Tunnel Construction Process, https://doi.org/10.1007/978-981-19-3474-2_8

141

142

8 Key Technologies for Foundation Pit Construction of Adjacent …

Fig. 8.1 Main research steps and contents

(2) (3)

Study evaluation index, determine the standard of monitoring in construction; The study of evaluation method is convenient for scientific prediction of tunnel safety impact before construction.

The third step is to study the indicators, monitoring methods and technical improvement that need to be monitored in the construction process measures. According to the field test laboratory test and numerical simulation and other means, research and development of adjacent tunnel construction foundation pit technology and technology and field monitoring technology.

8.2 Construction Technology and Technology of Foundation Pit …

143

8.2 Construction Technology and Technology of Foundation Pit of Adjacent Built Shallow Buried Tunnel 8.2.1 Simulation and Analysis of the Influence Process of Foundation Pit Excavation on Tunnel For rock hard “under” on soft soil typical engineering geological conditions, the dual structure in combination with a Qingdao terminal tunnel adjacent foundation pit engineering, true three-dimensional numerical model is established using Midas software, dynamic simulation block, layering excavation process, actual state, has been approved for tunnel, and in the later process affected by the excavation of adjacent state. The finite element simulation can be divided into three stages: the first stage simulates the initial in-situ stress stage before tunnel excavation; The second stage is tunnel excavation process simulation; In the third stage, the excavation process is simulated. 1.

Model establishment and construction process simulation

Considering the influence range of foundation pit excavation, a true threedimensional model was adopted for the model. The length × width × height of the model was set as 270 m × 250 m × 56 m. The model adopted four-sided solid elements with a total number of 90,635 elements and 24,226 nodes (Fig. 8.2). In order to accurately simulate the stress state of the tunnel before excavation, the actual opening process of the tunnel is simulated. Before tunnel excavation, horizontal displacement constraints are applied around the model, vertical displacement constraints are applied at the bottom, and the upper boundary is free boundary. The initial load is divided into two parts. The first part is the self-weight load of the overlying rock layer, and the second part is the load of the adjacent existing buildings, which are both brick-concrete structures with 12 floors and 7 floors respectively Floor, according to the building structure design code, the gravity load per unit area Fig. 8.2 Stereo diagram of finite element model

144

8 Key Technologies for Foundation Pit Construction of Adjacent …

of the structure (including live load) is 12–14 kN/m2 , which is uniformly taken as 12 kN/m2 . At this time, the element stress is retained and the displacement is cleared. In order to ensure the accuracy of the finite element model analysis and take into account the complexity of the actual construction conditions and geological conditions on site, the actual project is appropriately simplified: (1)

(2)

(3)

(4)

Based on the actual borehole information, the finite element model of stratification was established. Since the overall topography of the site was relatively slow, it was assumed that the surface and all soil layers were uniformly distributed horizontally. Because there is no rich aquifer in the project, the underground is mainly the bedrock fissure water and the upper stagnant water, and the influence of the change of groundwater level on the excavation of tunnel and foundation pit is ignored. In the process of modeling, the excavation, the perimeter of the foundation pit, the surrounding area of the existing building foundation and the surrounding area of the tunnel hole need to be divided into dense grids. Using Mohr-Coulomb criterion, the underground diaphragm wall of tunnel lining and foundation pit retaining structure is simulated, and the implantable truss is used to simulate the tunnel bolt and foundation pit retaining bolt.

The tunnel excavation is carried out by the method of upper and lower steps, and the simulation construction stage is 1–22 stages. After the completion of the tunnel excavation, the quasi-actual tunnel deformation and stress state can be obtained, which can be approximately regarded as the in-situ stress state before the excavation of the foundation pit. After the completion of tunnel excavation, the base side excavation and support are carried out in the existing tunnel state. Each layer is divided into 6 pieces and 3 layers in the open force state. On this basis, the foundation pit excavation is carried out. After the completion of tunnel excavation, the foundation pit excavation and support will be carried out under the existing tunnel condition. Layered excavation, block excavation and support will be adopted. Each layer is divided into 6 blocks, which will be excavated in 3 layers and each layer will be excavated at 2 m. Before excavation, 1 m thick composite ground wall is used as the retaining body around the foundation pit to pre-reinforce and stop the water around the soil. The pit wall is enclosed by prestressed anchor rod with horizontal spacing of 2 m, inclination of 20°, length of 13 m, length of anchor end of 5 m and length of free end of 8 m. A total of three layers of anchor rod are played. According to different construction stages of foundation pit excavation, the specific excavation construction method is listed in Table 8.1, and the construction stage is from 23 to 38 stages. 2.

Engineering geological conditions and rock and soil layer parameters

The site geological prospecting data show that the stratum of the site is composed of Quaternary soil and bedrock. The Quaternary thickness is small in the east of the site and gradually increases in the west. The eastern side of the site is composed of Holocene artificial filling soil, and the western side is mainly composed of Holocene

8.2 Construction Technology and Technology of Foundation Pit …

145

Table 8.1 Construction method of foundation pit excavation The construction phase

23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38

Excavation first floor

1

Excavation second layer

2

3

4

5

6

1

2

3

4

5

6

1

2

3

4

5

Excavation of the third layer The first layer of supporting bolt

1

The second layer of supporting bolt

6

2

3

4

5

6

1

2

3

4

5

6

1

2

3

4

5

Bolt support three layers

6

artificial filling soil, Holocene Marine sedimentary layer and Upper Pleistocene flood alluvial layer. The underlying bedrock is mainly coarse-grained granite in the late Yanshanian period, partially interspersed with lamprophyre and fine-grained granite dikes intruded in the late Yanshanian period. The order of rock and soil layer from top to bottom is as follows: (1) The layer of plain filling is about 4 m thick; The second layer is silty clay with a thickness of about 2 m. The third layer contains clay coarse gravel sand with a thickness of about 1 m. The fourth layer is strongly weathered coarse-grained granite with a thickness of about 4 m. The middle weathering zone of the coarse-grained granite in the ➄ layer, with a thickness of about 7 m; The sixth layer coarse-grained granite breezy zone. The main physical and mechanical parameters of each layer are listed in Table 8.2. 3.

Finite element analysis of calculation results

After taking the central axis of the foundation pit of the building and the section plane y = 135 m in the longitudinal and vertical direction of the tunnel, the position force analysis was carried out. The position relationship between the tunnel profile Table 8.2 For physical and mechanical parameters of each rock and soil layer Level number

Density (kN/m2 )

Elasticity modulus (GPa)

Poisson’s ratio

cohesive force Frictional (MPa) angle (°)

Strength of extension (MPa)

➀

17.6

0.01

0.005

0.004

18

0.004

➁

19.2

0.005

0.004

0.047

15

0.003

➂

19.8

0.03

0.02

0.02

35

0.01

➃

22.1

1.2

0.6

0.6

45

0.2

➄

23.4

2.25

2.3

1.18

55

1.8

➅

24.7

13.9

2.0

70

4.5

15.8

146

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Fig. 8.3 Section of relative position of foundation pit and tunnel

and the foundation pit at y = 135 m is shown in Fig. 8.3. The number of monitoring points around the tunnel and on the arch from left to right are 6 nodes 1, 2, 3, 4, 5 and 6, respectively. The number of monitoring points at the bottom of the tunnel from right to left are 5 nodes 7, 8, 9, 10 and 11, respectively, as shown in Fig. 8.3. Tunnel convergence deformation: after the completion of tunnel excavation, clearance convergence displacement appears in the circumferential tunnel. According to the monitoring points 1 and 6, tunnel convergence in the horizontal direction is 5.2 mm; According to the monitoring point 3, the maximum vertical settlement of the vault is 8.4 mm; According to the monitoring point 9, the maximum uplift of the arch bottom is 11.9 mm; Compared with the convergence value after the completion of excavation, the tunnel convergence deformation caused by the completion of excavation has little change, that is, the tunnel convergence deformation basically stops after the completion of tunnel construction, and the excavation process has little effect on the tunnel convergence deformation. Tunnel displacement: because of the influence of excavation unloading, and foundation pit side wall and bottom soil mass medial to the foundation pit deformation, cause the displacement of surrounding soils produce bias foundation pit side, resulting in the tunnel as a whole to the side of lateral displacement of foundation pit, and the overall service trend, Figs. 8.4 and 8.5 for the vertical displacement and horizontal displacement nephogram. Vertical displacement data around the tunnel were extracted to obtain displacement curves in Figs. 8.6 and 8.7. According to Figs. 8.6 and 8.7, the vertical displacement of the tunnel after the excavation of the foundation pit, compared with that before the excavation of the foundation pit, moves upward as a whole. The lift of the side close to the foundation pit is greater than that of the side far away from the foundation pit, with an average upward movement of 1.0 mm. After calculation, the vertical deformation curvature radius of the tunnel is

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Fig. 8.4 Vertical displacement cloud diagram after excavation of foundation pit

Fig. 8.5 Cloud image of horizontal displacement after excavation of foundation pit

700,967 m, greater than 15,000 m, which meets the control requirements of tunnel protection. Figures 8.8 and 8.9 displacement curves were obtained by extracting the horizontal displacement data around the tunnel. As can be seen from Fig. 8.8 and Fig. 8.9, after excavation of the foundation pit, compared with before excavation of the foundation pit, the overall displacement of the tunnel moves towards the direction of the foundation pit horizontally on average by 0.58 mm. Tunnel stress analysis: After the completion of foundation pit excavation, the maximum principal stress distribution is shown in Fig. 8.10. The stress curve is

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Fig. 8.6 Peripheral monitoring of tunnel at y = 135 m vertical displacement curve of measuring point

Fig. 8.7 Tunnel arch bottom at y = 135 m vertical displacement curve of monitoring points

Fig. 8.8 Tunnel hole at y = 135 m horizontal displacement curve of circumferential monitoring points

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Fig. 8.9 Tunnel arch bottom at y = 135 m horizontal displacement curve of monitoring points

Fig. 8.10 The maximum principal stress of surrounding rock after excavation

obtained by extracting the rock stress data around the tunnel hole, as shown in Fig. 8.11. The results show that after the excavation of the proposed foundation pit, the surrounding rock pressure is released, and the stress is the largest at the shoulder and the arch, and the least at the arch foot. The stress concentration area is formed at the arch foot. The arch foot near the foundation pit has a maximum stress of 0.5 MPa, and the shear stress on the tunnel is shown in Fig. 8.12. It can be seen from Fig. 8.12 that the maximum internal shear force after foundation pit excavation is completed is shown in Fig. 8.13. It can be seen from Fig. 8.13 that the foundation pit force is 0.36 MPa. The internal forces on the tunnel lining are shown in Fig. 8.13. As can be seen from Fig. 8.13, after the completion of foundation pit excavation, the maximum

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Fig. 8.11 The maximum principal stress of surrounding rock at different construction stages at y = 135 m

Fig. 8.12 Shear forces on tunnel lining after foundation pit excavation y = 135 m

internal force is 1.23Mpa, which does not exceed the design value of C35 concrete 2.2Mpa, and no crack of more than 0.2 mm will be generated on the lining. Therefore, the influence of engineering construction on tunnel cracks is safe.

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Fig. 8.13 Internal forces on tunnel lining after foundation pit excavation y = 135 m

8.2.2 Temporal and Spatial Effect of Foundation Pit Excavation and Influence of Construction Technology 1.

The influence of different layer thickness on tunnel in foundation pit excavation

The influence of three conditions of excavation thickness of 2 m, 3 m and 6 m on adjacent existing tunnels is simulated respectively. The calculation results are shown in Figs. 8.14, 8.15, 8.16, 8.17, 8.18, 8.19, 8.20, 8.21 and 8.22. The above cloud images and deformation law analysis results show that: In the unique geological conditions in Qingdao area, combined with the actual engineering conditions (excavation depth 6 m), layered section excavation, simulation process in boundary conditions, load control, grid size, rock and soil layer properties under the condition of invariable, the size of the partitioned excavation,

Fig. 8.14 Cloud image of vertical displacement of tunnel when layered excavation with different thicknesses: a excavation thickness 2 m; b excavation thickness 3 m; c excavation thickness 6 m

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Fig. 8.15 Vertical displacements around tunnels with different thicknesses excavated in layers

Fig. 8.16 Vertical displacements of bottom of arch tunnels with different thicknesses excavated in layers

Fig. 8.17 Horizontal displacement cloud of tunnels with different thicknesses excavated in different layers

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Fig. 8.18 Horizontal displacements around tunnels with different thicknesses excavated in layers

Fig. 8.19 Horizontal displacement of arch bottom of tunnel with different thickness excavated in layers

Fig. 8.20 Cloud map of the maximum principal stress in the surrounding rock of the tunnel when layered excavation is of different thicknesses: a excavation thickness 2 m; b excavation thickness 3 m; c excavation thickness 6 m

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Fig. 8.21 The maximum principal stress of tunnel surrounding rock when the foundation pit is excavated in layers with different thicknesses

Fig. 8.22 Tunnel lining internal forces and shear force nephogram with different thickness of foundation pit excavation: a internal force with excavation thickness of 2 m; b internal force of 3 m in excavation thickness; c internal force with excavation thickness 6 m; d shear force with excavation thickness of 2 m; e shear force with excavation thickness of 3 m; f excavation thickness 6 m shear force

different thickness of the foundation pit excavation of tunnel convergence deformation, vertical displacement and horizontal displacement and stress of surrounding rock and lining shear force and internal force effect is very small, instructions for the practical engineering, the excavation depth under certain conditions, each layer excavation thick Degree is not the dominant factor affecting the normal operation

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of the tunnel. This study can guide the excavation of foundation pit in practice and provide a favorable basis for accelerating the engineering process. 2.

Influence of different depth of foundation pit excavation on tunnel

Based on this project example, in order to provide reference for similar projects, further research is carried out here, namely, three working conditions of 6 m, 12 m and 17 m excavation depth are simulated respectively to analyze the influence of different excavation depths on the deformation and stress of adjacent existing tunnels. The calculation results of vertical and horizontal displacements are shown in Fig. 8.23. See Fig. 8.23 for the cloud diagram of vertical displacement and Fig. 8.26 for the cloud diagram of horizontal displacement when the foundation pit is excavated at different depths. The vertical displacement data around the tunnel and at the bottom of the arch were extracted to obtain the displacement curves in Figs. 8.24 and 8.25. The horizontal displacement data around the tunnel and at the bottom of the arch were extracted to obtain the displacement curves in Figs. 8.27 and 8.28. As can be seen from Figs. 8.24 and 8.25, compared with the excavation before the foundation pit, the vertical displacement of the tunnel at different excavation

Fig. 8.23 Tunnel vertical displacement cloud diagram at different depth of foundation pit excavation: a excavation depth 6 m; b excavation depth 12 m; c excavation depth 17 m

Fig. 8.24 Vertical displacement curves around the tunnel at different excavation depths

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Fig. 8.25 Vertical displacement curves of tunnel arch bottom at different excavation depths

Fig. 8.26 Tunnel horizontal displacement cloud map at different depth of foundation pit excavation: a excavation depth 6 m; b excavation depth 12 m; c excavation depth 17 m

Fig. 8.27 Horizontal displacement curves around the tunnel at different excavation depths

depths moves upward as a whole, and the lift of the side near the foundation pit is greater than that far away from the foundation pit. In addition, with the increase of the excavation depth, the lift of the monitoring points around the tunnel is more and more obvious, while the monitoring points at the bottom of the tunnel are slightly raised. When the excavation depth is 6 m, the tunnel moves upward by 1.0 mm on average. When the depth of excavation is 12 m, the average upward movement of

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Fig. 8.28 Horizontal displacement curves of tunnel arch bottom at different excavation depths

the tunnel is 1.35 mm. When the depth of foundation pit is 17 m, the average upward movement of the tunnel is 3.21 mm. As can be seen from Figs. 8.27 and 8.28, when the excavation depth of the foundation pit is 6 m, the tunnel moves 0.58 mm horizontally to one side of the foundation pit. When the excavation depth is 12 m, the tunnel moves 1.67 mm horizontally to one side of the foundation pit. When the depth of the foundation pit is 17 m, the whole tunnel moves 3.95 mm horizontally toward the water at one side of the foundation pit. From the above horizontal and vertical displacement cloud maps and deformation curves, it can be seen that different depth of foundation pit excavation has great influence on tunnel deformation, and the deeper the foundation pit excavation is, the more obvious the influence is. Since the initial in-situ stress state, tunnel excavation process and foundation pit excavation process are considered in the modeling process, the realization time of the three modeling processes is continuous. In the initial stress state, the horizontal and vertical displacements of each monitoring point are 0; After tunnel excavation, tunnel clearance section converges, and each monitoring point has horizontal and vertical displacement of different degrees; After the excavation of the foundation pit, the lateral wall and the soil at the bottom of the foundation pit will deform towards the inside of the foundation pit, which causes the whole tunnel to have transverse displacement towards the side of the foundation pit, and the whole tunnel tends to float upwards. The deformation generated by the tunnel is spatially manifested as oblique displacement towards the bottom of the pit. As for the vertical displacement of the tunnel, with the increase of the excavation depth, the vertical displacement of the monitoring point near the foundation pit increases obviously, showing obvious spatial effect. For the horizontal displacement of the tunnel, it shows the overall displacement to the side of the foundation pit. The cross-section at y = 135 m was selected to obtain the maximum principal stress distribution at different excavation depths, as shown in Fig. 8.29. The stress data around the tunnel were extracted to obtain the stress curve, as shown in Fig. 8.30.

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Fig. 8.29 Cloud map of the maximum principal stress in tunnel surrounding rock at different excavation depths: a excavation depth 6 m; b excavation depth 12 m; c excavation depth 17 m

Fig. 8.30 Maximum principal stress of tunnel surrounding rock at different excavation depths

According to the stress curve in Fig. 8.30, when the depth of the foundation pit is 6 m, the unit stress corresponding to each monitoring point changes regularly. The arch and the shoulder have the greatest stress release, and the maximum principal stress after release is 0.145 MPa; When the depth of the foundation pit is 12 m, a large stress release occurs at the No.6 monitoring point of the arch shoulder of the tunnel far from the foundation pit, and the maximum principal stress after the release is 0.093 MPa, while the stress concentration appears at the vault position. When the depth of the foundation pit is 17 m, the stress concentration of the vault is more obvious. When the excavation depth is 17 m, the stress concentration of the arch is more obvious, and the maximum stress release is transferred to the No. 5 monitoring point closer to the foundation pit. With the increase of excavation depth, the stress release of each monitoring point at the bottom of the arch decreases, and the stress concentration is obvious. The calculation results of internal forces of adjacent existing tunnel lining at different excavation depths are shown in Figs. 8.31 and 8.32. As can be seen from Fig. 8.31, different excavation depths have little influence on the internal forces of tunnel lining, and none of them exceed the design value of C35 concrete at 2.2 MPa. When the depth of foundation pit is 6 m, the maximum lining internal force is 1.23 MPa; When the depth of foundation pit is 12 m, the maximum lining internal force is 1.12 MPa. When the depth of foundation pit is 17 m, the maximum lining internal force is 1.21 MPa. Figure 8.32 shows that the maximum shear stress on

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Fig. 8.31 Cloud map of tunnel lining internel force at different excavation depths: a excavation 6 m; b 12 m excavation; c excavation 17 m

Fig. 8.32 Cloud map of tunnel lining shear force at different excavation depths: a excavation 6 m; b 12 m excavation; c excavation 17 m

tunnel lining increases with the increase of foundation pit excavation depth. When the depth of foundation pit is 6 m, the maximum lining internal force is 0.32 MPa. When the excavation depth is 12 m, the maximum lining internal force is 0.35 MPa. When the depth of foundation pit is 17 m, the maximum lining internal force is 0.38 MPa. 3.

Influence of different horizontal distance between foundation pit and tunnel on tunnel

The excavation thickness of blocks, excavation depth of foundation pit, excavation size of each block, model boundary condition, load, grid size, soil layer property and supporting form are kept unchanged. The distance between foundation pit and tunnel is respectively simulated by MIDAS/GTS finite element analysis software, which is 13 m, 8 m and 3 m, and the displacement calculation results are shown in Figs. 8.33, 8.34, 8.35, 8.36, 8.37 and 8.38. The analysis results show that: from the above displacement curve, for the vertical displacement of the tunnel, at the same excavation depth, the closer the horizontal distance between the foundation pit and the tunnel, the more obvious the vertical displacement of the tunnel, and the greater the vertical displacement of the tunnel monitoring point on the side near the foundation pit, showing an obvious spatial effect. As for the horizontal displacement of the tunnel, the monitoring points 2,

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Fig. 8.33 Tunnel vertical displacement cloud map at different horizontal distances: a 13 m apart; b 8 m apart; c 3 m apart

Fig. 8.34 Vertical displacement curves around the tunnel at different horizontal distances

Fig. 8.35 Vertical displacement curves of tunnel arch bottom at different horizontal distances

3, 4 and 5 around the tunnel do not change significantly with the increase of the distance, while the monitoring points 1 and 6 at the shoulder show certain convergence compared with that after tunnel excavation, and the convergence becomes larger with the increase of the depth. When the distance between the foundation pit and the tunnel is 3 m, the chord length of No.1 monitoring point and No. 6 monitoring point converges 2.1 mm horizontally. It is worth noting that for No. 1 monitoring point, when the distance between the foundation pit and the tunnel is

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Fig. 8.36 Tunnel horizontal displacement cloud map at different horizontal distances: a 13 m apart; b 8 m apart; c 3 m apart

Fig. 8.37 Horizontal displacement curves around the tunnel at different horizontal distances

Fig. 8.38 Horizontal displacement curves of tunnel arch bottom at different horizontal distances

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3 m, the vertical displacement of the tunnel is close to 0. If the distance is closer, then the No. 1 monitoring point will rebound compared with the tunnel after excavation, which is detrimental to the safety of the tunnel structure. Therefore, for the unique geology of Qingdao, when the excavation depth is 6 m, the excavation within 3 m from the tunnel should be avoided. When the distance between foundation pit and tunnel is 13, 8 and 3 m, the calculation results of surrounding rock stress and internal force on tunnel lining are shown in Figs. 8.39, 8.40, 8.41 and 8.42. As can be seen from Figs. 8.39 and 8.40, the excavation of the foundation pit leads to the release of stress in the surrounding rock of the tunnel to varying degrees. The release of stress in the vault is more obvious, and the stress concentration in the arch foot is obvious. The stress concentration at the bottom of the pit is observed at the monitoring point of No.3, and the closer the foundation pit is to the tunnel, the more obvious the stress concentration at the bottom is. As can be seen from Fig. 8.41, different horizontal distances between the foundation pit and the tunnel have little influence on the internal forces of the tunnel lining, which do not exceed the design value of 2.2 MPa for C35 concrete. When the distance between the foundation pit and the tunnel is 3 m, the maximum internal forces of the lining are 1.2 MPa. As can be seen from Fig. 8.42, with the continuous decrease of different horizontal distances between the foundation pit and the tunnel, the shear force on the tunnel lining has an increasing trend. When the

Fig. 8.39 Cloud map of the maximum principal stress in tunnel surrounding rock at different horizontal distances: a 13 m apart; b 8 m apart; c 3 m apart

Fig. 8.40 The maximum principal stress of tunnel surrounding rock at different horizontal distances

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Fig. 8.41 Cloud image of internal forces on tunnel lining at different horizontal distances: a 13 m apart; b 8 m apart; c 3 m apart

Fig. 8.42 Shearing force on tunnel lining at different horizontal distances (I): a 13 m apart; b 8 m apart; c 3 m apart

distance between the foundation pit and the tunnel is 13 m, the maximum shear force on the tunnel lining is 0.32 MPa, and when the distance between the foundation pit and the tunnel is 8 m, the maximum shear force on the tunnel lining is 0.38 MPa When the distance between the foundation pit and the tunnel is 3 m, the maximum shear force on the tunnel lining is 0.42 MPa. 4.

Influence of different excavation space size on tunnel

Under the condition that the thickness of block excavation, the depth of foundation pit excavation, the distance between foundation pit and tunnel, the boundary condition of model, the size of load grid, the property of soil layer and the supporting form remain unchanged, the MIDAS/GTS finite element analysis software is used to simulate the excavation of foundation pit into 6 blocks, 4 blocks, 2 blocks and 1 blocks respectively. As for the influence of block excavation on the adjacent existing tunnel, the displacement calculation results are shown in Figs. 8.43, 8.44, 8.45, 8.46, 8.47 and 8.48. After the completion of tunnel excavation, when the excavation of the foundation pit is carried out, the vertical displacement rebound value of the side near the foundation pit of the tunnel is larger than that of the other side. At the same time, the tunnel vault appeared to float. With the increase of the block, the rebound value decreases. It shows that increasing the number of excavation blocks can effectively reduce the

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Fig. 8.43 Tunnel vertical displacement cloud map with different excavation space sizes (2): a one piece; b divided into 2 pieces; c in four pieces; d in six pieces

Fig. 8.44 Vertical displacement curves around the tunnel with different excavation space sizes

vertical rebound effect caused by excavation. With the increase of excavation blocks to 6 blocks, the rebound value tends to be stable. After the completion of tunnel excavation, with the increase of excavation blocks, the rebound value of horizontal displacement around the tunnel decreases. It shows that the horizontal displacement rebound effect can be effectively reduced by

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Fig. 8.45 Vertical displacement curves of tunnel arch bottom with different excavation space sizes

Fig. 8.46 Tunnel horizontal displacement cloud map with different excavation space sizes: a Excavation in one block; b Excavation in 2 blocks; c excavation in four blocks; d excavation in six blocks

increasing the number of excavation blocks, and the rebound value tends to be stable with the increase of excavation blocks to 6. The calculation results of the influence of different excavation Spaces on the tunnel, surrounding rock stress and lining internal force are shown in Figs. 8.49, 8.50 and 8.51. As can be seen from the figure, with the increase of the number of excavation

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Fig. 8.47 Horizontal displacement curves around the tunnel with different excavation space sizes

Fig. 8.48 Horizontal displacement curves of tunnel arch bottom under different excavation space sizes

blocks, the maximum principal stress of tunnel surrounding rock gradually decreases, the change of tunnel lining internal force gradually increases, reaching 1.22 MPa, and the shear stress of tunnel lining gradually decreases from 1.76 MPa to 0.32 MPa. It can be seen that increasing the number of excavated blocks can reduce the influence on the adjacent existing tunnels.

8.2.3 New Method of Progressive Step Excavation According to the typical geological conditions of the soil and rock binary structure, a new method of progressive layered excavation is used to excavate the foundation pit near the tunnel in operation, as shown in Fig. 8.52, which is the position relationship between the foundation pit and the tunnel. The implementation principle of this method is as follows: progressive stratification, shallow excavation in blocks, short separation and quick support, frequent measurement and feed-back. For the foundation pit with a small area, the progressive step excavation can be done in layers (Fig. 8.53); For the foundation pit with small area and the foundation pit with large

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Fig. 8.49 Cloud map of the maximum principal stress in surrounding rock of tunnels with different excavation blocks: a excavation in one block; b excavation in 2 blocks; c excavation in four blocks; d excavation in six blocks

area, the progressive step excavation is carried out by step and step and block excavation (Fig. 8.54). Progressive steps refer to the layered excavation from the foundation pit far away from the tunnel to the foundation pit near the tunnel. Shallow block excavation means that for a large area of foundation pit, block excavation is adopted, the length of each block is not more than 20 m, the width is not more than 20 m, shallow excavation is. Shallow excavation, the excavation depth of each layer is not more than 3.0 m (the volume of each block excavation is not more than 1200 m3 ).Short interval and quick support refers to the short exposure gap of rock and soil mass after excavation, so temporary support can be carried out quickly. Frequent measurement refers to the frequent monitoring of the displacement and stress changes of rock and soil during the construction process, and timely feedback of monitoring information, so as to dynamically grasp the excavation situation and do a good job in disaster prevention and mitigation. In this method, when the depth of the foundation pit is not greater than 6m, the direct connection is excavated in 2 layers. The upper soil layer is operated by excavator, and the lower rock layer is operated by hydraulic splitter. The hydraulic splitting machine has the characteristics of small volume, light weight, strong power,

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Fig. 8.50 Tunnel lining internal forces with different numbers of excavated blocks: a excavation in one block; b excavation in 2 blocks; c excavation in four blocks; d excavation in six blocks

no vibration, no impact, no noise, no dust, high working efficiency and remarkable working effect. Comparison of several common rock splitting processes is shown in Table 8.3. When the depth of the foundation pit is greater than 6 m, the excavation is carried out in layers according to the thickness of the soil layer. The upper soil layer is operated by excavator, and the lower rock layer is operated by hydraulic splitter. When the area is large, each layer is excavated by the method of interblock excavation. The excavation depth of the first layer is from the ground to the first layer, the excavation depth of the middle layers is the vertical spacing between the two adjacent supports, and the excavation depth of the last layer is the bottom of the last layer. The height difference between each layer block and adjacent layer block is not more than 6 m. After excavation to the bottom of the foundation pit, the building foundation construction. In order to prevent the uplift of the bottom of the foundation pit, the intermediate supporting piles and columns are poured or laid at the relevant positions inside the building (the intersections of columns or partitions, etc.), and then the beam slab floor structure of the foundation and ground layer is constructed, and then the excavation is carried out in layers and blocks.

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Fig. 8.51 Cloud map of tunnel lining shear force with different excavation blocks: a excavation in one block; b excavation in 2 blocks; c excavation in four blocks; d excavation in six blocks Fig. 8.52 Schematic diagram of the relationship between foundation pit and tunnel position

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Fig. 8.53 Schematic diagram of progressive layered foundation pit excavation

Fig. 8.54 Diagram of block excavation of foundation pit

Before the actual excavation, it is necessary to analyze the influence of foundation pit, tunnel deformation and underground water system change according to the geological prospecting data and tunnel data, and determine the excavation size and thickness of blocks of the progressive layered excavation method. In the process of foundation pit excavation, if it is found that the deformation of the tunnel or the soil around the foundation pit is too large, the excavation thickness and excavation area of the subsequent block excavation can be reduced to reduce the tunnel deformation.

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Table 8.3 Comparison of several common rock splitting processes Rock fragmentation process Advantage

Disadvantages

Manual pick

The workers are skilled in construction

The work efficiency is low, the construction period is long, the cost is high

Blasting work

Fast

1. The excavation face is not easy to control and has a certain risk 2. Blasting vibration is difficult to control and has a great impact on adjacent foundation construction, which requires expert demonstration in advance 3. Explosive equipment and explosives are strictly controlled 4. With large external interference, it is necessary to avoid the peak hours before blasting

Hydraulic splitter

Easy to operate, high efficiency, fast speed, can be effective and fast progress, no noise, no pollution during construction. Can effectively save the cost

1. The diesel engine is not easy to start when used in winter 2. Some connecting accessories need constant maintenance and adjustment

8.3 Evaluation of the Impact of Foundation Pit Construction on the Safety of Adjacent Tunnels 8.3.1 Qualitative and Quantitative Analysis Method for the Influence of Foundation Pit Construction on Adjacent Tunnels Qualitative analysis is made according to stress diffusion lines of each rock and soil layer, and the process is shown in Fig. 8.55. The specific steps are: According to the spatial layout design of the proposed building and the spatial position of the existing tunnel, draw the profile of the foundation pit of the building and the adjacent existing operating tunnel; According to the Code for Design of Building Foundation GB50007-2011 and combined with the results of geological prospecting report, the stress diffusion lines of each rock and soil layer were drawn (Fig. 8.56) according to the requirements of the code. If the stress diffusion line of the rock and soil layer does not intersect with the existing tunnel, then the construction has no influence on the adjacent existing tunnel, and the spatial layout is considered feasible. If the stress diffusion line of the rock layer intersects the existing tunnel, then the construction has an impact on the adjacent

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Fig. 8.55 Prediction flow of the impact of construction on an adjacent existing tunnel

Fig. 8.56 Schematic diagram of stress diffusion line determination of adjacent existing tunnel during construction

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existing operating tunnel, which needs to be further measured and the construction unit is required to take corresponding measures to reduce the impact. On the basis of qualitative analysis, if the stress diffusion lines of each rock layer have influence on the adjacent existing operating tunnels, the influence analysis is required. The Mindlin solution was integrated with mathematical software in the excavation area of the foundation pit to obtain the additional stress and additional displacement of the adjacent existing tunnel caused by construction.

8.3.2 Safety Impact Assessment Index The evaluation index of the impact of foundation pit excavation on adjacent tunnels consists of two parts: one is the evaluation index of tunnel deformation; The second is the evaluation index of foundation pit deformation. The two parts are evaluated simultaneously as a comprehensive evaluation index of the influence of foundation pit excavation on adjacent tunnels. 1.

Evaluation index of tunnel deformation

Including surface settlement, tunnel cumulative absolute settlement, horizontal displacement, curvature radius of deformation curve. The absolute settlement and horizontal displacement of tunnel structural facilities shall not be greater than 20 mm (including the final displacement of various loading and unloading, which shall be controlled according to the total deformation of tunnel structural deformation influenced by engineering activities, rather than 20 mm for each project Therefore, this standard needs to determine all possible projects around the tunnel according to the planning, including the short-term and long-term ones, and then allocate the allowable amount of deformation, otherwise it will cause a large amount of deformation superposition); The uneven settlement must be controlled within 1.6‰; Settlement rate is 0.02 mm/d as the criterion to determine whether the tunnel is stable. The curvature radius of the tunnel deformation curve is R ≥ 15,000 m. The relative curvature of the tunnel should not be greater than 1/2500. The technical index of curvature radius of tunnel deformation curve mainly reflects the smoothness and deformation curvature of the longitudinal change of subway tunnel. The curvature radius of tunnel deformation curve is generally calculated by the measurement data arranged in the monitoring points in the tunnel. The relative bending technical index of the tunnel mainly reflects the relative bending degree of the subway tunnel, which generally takes the monitoring data of three adjacent monitoring points arranged on the track bed in the subway tunnel as the data analysis basis, and can directly detect the bending degree of the track. The additional load on the outer wall of subway tunnel caused by construction factors is no more than 20 kPa. The maximum uplift of the tunnel is 10 mm.

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Table 8.4 Monitoring requirements for foundation pit deformation Alarm value of horizontal displacement of foundation pit slope top

Alarm value of vertical displacement on top of foundation pit slope

Alarm value of foundation pit bottom heave

Cumulative value D (mm)

≤ 20

Rate of change V D (mm/D)

≤2

Error in deformation point coordinates

≤ 0.3

Cumulative value S (mm)

= 20

Rate of change V S (mm/d)

≤2

Error in elevation difference of deformation points

≤ 0.15

Cumulative value (mm)

≤ 10

Error in elevation difference of deformation points

≤ 1.0

The peak velocity of vibration tunnel caused by pile driving vibration and explosion is no more than 2.5 cm/s. 2.

Evaluation index of foundation pit deformation

For the foundation pit construction of adjacent tunnels, corresponding monitoring measures are also required. Considering the dual structure of soil and rock, the requirements in Table 8.4 should be met.

8.3.3 Assessment Method of Overall Stability of Adjacent Tunnels The evaluation of the overall stability of adjacent tunnels by foundation pit excavation can be divided into two processes: the first process is the evaluation of tunnel excavation process, and the second process is the secondary evaluation of tunnel safety based on the first process. In view of the typical geological conditions of “upper soft and lower hard”, combined with the engineering practice of the influence of foundation pit excavation on the stability of adjacent tunnels, a progressive fuzzy evaluation method for the stability of tunnels caused by foundation pit excavation is studied. Firstly, through comprehensive analysis of the factors affecting the stability of tunnel surrounding rock, the membership degree of each factor in the evaluation model is given according to the fuzzy comprehensive evaluation theory, so as to evaluate the stability of tunnel after completion; Secondly, on this basis, the change of the influence factors of the excavation of the building foundation pit on the adjacent tunnel is further considered and the membership degree is redetermined. The analytic hierarchy process is used to further qualitatively evaluate the stability of the tunnel, and the qualitative evaluation of the stability of the existing tunnel is obtained. Combined with the actual project in Qingdao, the results show that the excavation of the foundation pit will

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Table 8.5 The influence factors of tunnel surrounding rock stability Influence factor

Security level

Surrounding rock First level classification

The security level A dangerous level Hazard level Second level

Three-level

Level four

Degree of rock weathering

Nondevelopment The development Development of

A developmental

Underground water

Not obvious

More apparent

Obvious

Very clear

Construction factors

Good

preferably

Rather poor

Bad

cause the change of the influence factors of the tunnel and the change of the tunnel stability due to the negative environment effect; According to the special geological conditions in Qingdao area, this method can well reflect the influence of foundation pit excavation on the stability of the built tunnel, which makes the evaluation result more scientific and reasonable. Its main contents include: 1.

Factors influencing the stability of tunnel surrounding rock

The influence factors of tunnel surrounding rock stability are analyzed comprehensively, the safety grade is divided, and the fuzzy relationship between the main influence factors and tunnel surrounding rock stability is determined. See Table 8.5. 2.

Fuzzy comprehensive evaluation model of tunnel stability

According to the theory of fuzzy comprehensive evaluation, the fuzzy comprehensive evaluation model of tunnel stability is established, the membership degree of each factor in the evaluation model is given, and the qualitative evaluation of the stability of the built tunnel by the excavation of the foundation pit is obtained by the analytic hierarchy process. The progressive fuzzy evaluation method firstly evaluates the stability of the tunnel after completion, and then, on this basis, further considers the change of the influence factors of the excavation of the building foundation pit on the adjacent tunnel and redetermines the membership degree, so as to conduct the qualitative evaluation of the tunnel stability. The main contents of the fuzzy comprehensive evaluation model for tunnel stability are shown in Fig. 8.57. (1)

Establish evaluation factor set U

Fig. 8.57 Hierarchical analysis model of factors affecting the stability of surrounding rock

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8 Key Technologies for Foundation Pit Construction of Adjacent …

Stability evaluation of tunnel surrounding rock is a complex problem restricted and influenced by many factors. These factors have great fuzziness, and in many cases it is difficult to determine which factor is more important. Therefore, the analytic hierarchy process is adopted here to deal with these complex problems which are difficult to be fully quantitatively analyzed. The set of fuzzy associated factors can be expressed by U as: U = {U A , U B , UC , U D }

(8.1)

in the formula U A , U B , UC , U D are natural factors, engineering geological factors, hydrogeological factors and construction design factors. (2)

Conduct primary evaluation

The evaluation set is a set of all kinds of evaluation results that the evaluator may make to the evaluation object. For the stability classification of tunnel surrounding rock, the evaluation set can be expressed as the stability grade V of tunnel surrounding rock: V = {V A , VB , VC , VD }

(8.2)

in the formula V A , VB , VC , VD are the evaluation results of natural factors, engineering geological factors, hydrogeological factors and construction design factors. The fuzzy evaluation matrix is found and the fuzzy comprehensive evaluation model is established. The comprehensive evaluation can be made after the weight vector Ai is determined. The fuzzy comprehensive evaluation model is expressed as: Bi = Ai × Ri

(8.3)

The overall comprehensive evaluation result of the two-level evaluation is as follows: B = A×R

(8.4)

The fuzzy evaluation and treatment measures were obtained through the fuzzy vector uniformization, as listed in Table 8.6.

8.4 Research on Monitoring Technology in Foundation Pit Excavation In the process of foundation pit excavation, it will cause the unloading of rock and soil mass, and then affect the stress field and displacement field of the adjacent tunnel, so that the tunnel will be deformed and the tunnel operation safety will be affected.

8.4 Research on Monitoring Technology in Foundation Pit Excavation

177

Therefore, the stress and deformation monitoring of foundation pit and tunnel is very important. Table 8.6 Fuzzy evaluation and treatment measures Class

Evaluation value(F)

Acceptance level

Evaluate

Additional effect of foundation pit

Security

1–1.5

Ignore

The surrounding rock is more complete, generally will not be damaged, will not collapse

1–1.5 have no obvious effect The effect of 1.5–2.5 is obvious 2.5–3.5 have obvious influence 3.5–4 Strong effect

Relatively safe

More dangerous

1.5–2.5

2.5–3.5

Attention

Warning

The deformation of surrounding rock is large, but all of them are within the safety value. Local crushing of surrounding rock may cause collapse, so monitoring should be strengthened The deformation of surrounding rock is large and close to the safety critical value. The crushing of surrounding rock may lead to the overall collapse. Therefore, it is necessary to strengthen monitoring, do a good job in protection and evacuate non-construction personnel in the dangerous section

The effect of 1–1.5 is obvious 1.5–2.5 has no significant effect The effect of 2.5–3.5 is obvious 5–4 have obvious influence

1–1.5 have obvious influence The effect of 1.5–2.5 is obvious 2.5–3.5 have no obvious effect 3.5–4 has obvious influence

(continued)

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8 Key Technologies for Foundation Pit Construction of Adjacent …

Table 8.6 (continued) Class

Evaluation value(F)

Acceptance level

Evaluate

Dangerous

3.5–4.5

Alarm

The surrounding rock is seriously deformed, and a large area may collapse at any time. In addition to the full-time geological disaster safety personnel, monitoring and risk removal personnel, other people must evacuate to the safe area

Additional effect of foundation pit 1–1.5 Strong effect 1.5–2.5 have obvious influence 5–3.5 has obvious influence 3.5–4 have no obvious effect

8.4.1 Location of Monitoring Points The layout of monitoring points must conform to the deformation law of foundation pit and tunnel, so as to truly reflect the actual situation of the project and provide reliable technical support for practical decision-making, as shown in Fig. 8.58. The layout of monitoring points follows the following two principles: one is that the monitoring points should conform to the law of rock movement; the other is that the transverse section of the monitoring points in the foundation pit and the tunnel should be the same, and the vertical section should be parallel as far as possible. By analyzing the research results of geological conditions, rock strata movement rules and joint conditions, the settlement point layout is targeted to reflect the actual characteristics of foundation pit and tunnel deformation, and save the complicated workload caused by too many points layout.

8.4.2 Monitoring Items The monitoring project is divided into three parts: one is stress monitoring, two is displacement monitoring, three is groundwater level monitoring. The monitoring items listed in Table 8.7 are mainly carried out according to the grade of foundation pit and tunnel. According to the characteristics of the project examples in this chapter, in order to monitor the horizontal displacement of the foundation pit slope top with the baseline method, the project developed an auxiliary tool for monitoring the horizontal displacement of the foundation pit slope top and obtained the patent authorization, as shown in Figs. 8.59 and 8.60.

8.5 Conclusion

179

Fig. 8.58 Layout of monitoring points

8.5 Conclusion Qualitative and quantitative comprehensive evaluation methods were used to determine the impact of foundation pit excavation on the adjacent tunnels, and the secondary progressive evaluation method of foundation pit and tunnel was used to comprehensively evaluate the adjacent tunnels. In view of the typical geological conditions of soil and rock dual structure, a new method of progressive layered excavation is presented, which is used to excavate the foundation pit near the tunnel in operation. The practical research method of this project has a certain guiding significance for the construction of underground engineering under similar geological conditions.

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8 Key Technologies for Foundation Pit Construction of Adjacent …

Table 8.7 Monitoring items of foundation pit construction Monitoring project Foundation ditch

Monitored parameters Horizontal displacement of slope top Vertical displacement at the top of the slope The deep horizontal displacement of the enclosure wall Deep horizontal displacement of rock and soil mass Apophysis of pit bottom Groundwater leve Internal force of anchor bolt and soil nail Support the internal force

Tunnel

Foundation pit category First-level √

Two-level √

Three-level √

√

√

√

√

√

√

√

√

√

√

√

√

√

√

√

√

√

√

√

The vault, the base of the arch Hole in the week Second lining stress

Fig. 8.59 Ruler design drawing a top view; b front view; c elevated view; d left view

8.5 Conclusion

Fig. 8.60 Tripod construction

181

Chapter 9

Impact of High-Rise Construction on Adjacent Existing Tunnels

In the process of construction, new buildings will inevitably cause deformation of adjacent tunnels, and excessive deformation will endanger the structural safety and normal operation of tunnels [1–4]. Therefore, it is necessary to analyze the impact of new construction on the adjacent existing tunnel. Based on the background of an existing tunnel project adjacent to a new building construction project in Qingdao, this chapter, combined with MIDAS/GTS numerical simulation software, analyzes the influence of the construction of the new high-rise building structure and the use stage of the main structure after the roof sealing on the adjacent tunnel, and obtains the relevant rules of tunnel deformation.

9.1 Project Overview 1. New buildings and adjacent tunnels The new building project is a large-scale complex project. After the completion of the project, it will be a coastal public leisure area integrating commerce, office, catering and hotel, which will be dominated by middle and high-end residential areas. The project covers a total area of 22.8 hm2 , with an above-ground construction area of 800,000 m2 , an underground construction area of 400,000 m2 and a total construction area of 1.2 million m2 . The new building is planned to have 33 floors, 32 floors above ground, and 1 floor underground. The building height above ground is 96 m. The building foundation is pile foundation, and the excavation method of foundation pit is layered and block excavation. Just below the east side of the new building is a tunnel in Qingdao. The horizontal distance between the tunnel and the foundation pit of the new building is about 13 m, and the buried depth of the tunnel is 16 m. On the upper right of the tunnel are two existing buildings, building 1 is a 7-storey building on the ground, and building 2 is a 12-storey building on the ground, and the two existing buildings © China Architecture Publishing & Media Co., Ltd. 2022 D. Meng et al., Prediction and Control of Interaction Between Ground Building and Tunnel Construction Process, https://doi.org/10.1007/978-981-19-3474-2_9

183

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9 Impact of High-Rise Construction on Adjacent Existing Tunnels

are 10 m apart. To sum up, the plane position relation diagram of the building and the tunnel is shown in Fig. 9.1. The tunnel is approximately north–south, with a section height of 9.65 m, a span of 15.93 m and a total length of 25.1 km. The excavation method of the tunnel is to excavate the upper and lower steps, and the tunnel is supported in the form of anchor rod, and the spacing of the anchor rod is 1000 mm × 1000 mm. The supporting materials and parameters of the tunnel are listed in Table 9.1, and the supporting section of the tunnel is shown in Fig. 9.2. 2. Overview of site engineering geology According to geological exploration data, the geological main part of this area for the quaternary system with bedrock, especial terrain is relatively flat, and small, especial Fig. 9.1 Planar position relation diagram of new building and tunnel

Table 9.1 The supporting parameters of tunnel The type of support Materials and parameters Preliminary bracing The diameter of the hollow bolt is 25 mm, the concrete grouting is carried out in the bolt, the length of the bolt is 3.5 m; The tunnel wall is laid with a steel mesh with a diameter of 8 mm, and the spacing between the mesh is 200 mm × 200 mm. The arch is wet sprayed with C25 concrete, the concrete thickness H = 80 mm, and the steel arch is made of HPB235 steel The second line

Using C35 waterproof concrete, the thickness is 400 mm

9.1 Project Overview

185

Fig. 9.2 Support section of tunnel

things on both sides of the quaternary thickness difference is bigger, especial on the east side of the main components of quaternary system for artificial backfill soil, soil layer thickness is small, the west area of quaternary system main components for artificial backfill soil, holocene Marine sediments As well as Pleistocene alluvium, the thickness of the soil layer is larger, and below the soil layer is coarse-grained granite rock, which is partially interspersed with lamprophyre and fine-grained granite that invaded in the later period. The sequence of strata is as follows: ➀ miscellaneous fill soil; ➁ silty clay; ➂ the gravel sand; ➃ strongly weathered granite (coarse-grained); ➄ moderately weathered granite (coarse-grained); ➅ Breezy granite (coarse-grained). Physical and mechanical property parameters of each layer are listed in Table 9.2. Miscellaneous fill: it is distributed in the whole new site area, and the thickness distribution is thin in the east and thick in the west. The thickness of the thinnest soil layer on the east side is 1.20 m, and its elevation is −3.42 m. The thickness of the thickest soil layer on the west side is 6.70 m, and its elevation is 7.27 m. Noise color, humidity is between wet and saturated, rough and hard accounts for about 25%, the overall appearance of loose, its composition is mainly backfill soil, local occurrence of a small amount of construction (life) garbage. Silty clay: it mainly exists in a gully in the middle of the site. In other areas of the site, the thickness of the soil layer is smaller and the distribution is less. The overall continuity of the soil layer is relatively poor, and the average exploration thickness is about 2.0 m, grayish yellow, and the main composition is clay silt and gravel sand,

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9 Impact of High-Rise Construction on Adjacent Existing Tunnels

Table 9.2 For physical and mechanical properties of different layers Soil layers of no Weight γ (kN/m3 )

elasticity modulus E(MPa)

Cohesion of CC (kPa)

Poisson’s ratio of μ

Internal friction angle ϕ(◦ )

➀

17.5

10

10

0.35

10

➁

19.3

15

15

0.33

22

➂

19.6

35

37

0.30

24

➃

22.2

100

60

0.25

30

➄

23.5

500

85

0.23

32

➅

24.8

6000

100

0.21

35

of which the content of gravel sand is about 5%. The cut surface of the soil layer is smooth, with moderate toughness, high dry strength and plasticity. Gravel sand: it is mainly distributed in the B area of the new site. The average exploration thickness is about 2 m, and the color is mainly brown-yellow with gray, saturated and slightly dense. The main component of the grains is quartz, which is cemented and the grain grading is general. Strongly weathered granite (coarse grain): distributed in the whole field, brown to brown yellow, survey thickness of 0.3–20.7 m, coarse granular structure, structure is mainly massive; The main components of the mineral are feldspar and quartz, and the fissures are densely developed. There is a layer of oxide on the fissures and the color is black. The upper core is sandy and the lower core is breccia ~ coarse sand. On the hardness of rock mass, it is judged to be extremely soft rock, and the rock mass is relatively broken, and it is structural rock mass in the form of dispersion. Medium weathered granite (coarse-grained): distributed in the whole site, fleshy red, coarse-grained structure, mainly massive structure, survey thickness of 0.20– 16.8 m; The main components of the mineral are feldspar and quartz, and the joints are well developed. There is rust oxide on the developing surface of the joints, and there is no other filling material in the joints. The rock core is patchy ~ blocky by hand rubbing, and the sound of hammering the rock mass is dumb. The hardness of the rock mass is determined to be soft rock, and the rock mass is broken, and it is a massive structural rock mass with cataclastic shape. Breezy granite (coarse-grained): distributed in the whole field, light red, coarsegrained structure, structure is mainly massive; The main components of the mineral are feldspar and quartz. The alteration characteristics of the mineral are not obvious. The joint development is general, the joint surface is smooth and straight, and there is no other filling material in the joint. The rock core presented a short columnar ~ columnar shape by hand rubbing, and the sound of hammering the rock mass was clear. The integrity of the rock mass was good, and the rock mass was judged as hard rock in the hardness. 3. Hydrogeology of the site

9.2 Establishment of Finite Element Model

187

Referring to the survey report, it can be seen that the types of inland water in the depth range required for investigation are mainly fissure water, accompanied by pore water. The buried depth of the stable groundwater level detected by the borehole is 2.2–4.1 m, and the elevation of the stable groundwater level is 1.0 m. According to the borehole exploration, the groundwater in the side near the sea of the site is connected with the sea water. With the change of sea tide, the groundwater level also changes accordingly. According to the detection, the variation range of groundwater with the sea tide is about 2.5 m. The permeability of bedrock is weak and not good. To sum up, under the premise of ensuring the smooth excavation of the foundation pit of the new building and combining with the actual conditions of the construction site, the foundation pit dewatering scheme of the project adopts the light well point dewatering scheme. The well point pipe is made of steel pipe with a diameter of 45 mm, the connecting pipe is made of PVC pipe with a diameter of 45 mm, the water collecting pipe is made of steel pipe with a diameter of 100 mm (with joints), and the filter material is made of stones with a mud content of less than 1% and a particle size of 0.45–3.0 cm. 4. Layout of foundation pit monitoring points for new buildings Regardless of settlement observation of surrounding buildings, observation points are arranged as follows: horizontal displacement observation points on the top of the foundation pit are distributed around the foundation pit, with a total of 17 monitoring points numbered HV3 ~ HV19. Among them, observation points numbered HV10 ~ HV14 are located on one side of the tunnel and have a small horizontal distance from the tunnel. The vertical displacement observation points of the foundation pit slope top are followed by the horizontal displacement observation points of the slope top. The surrounding surface settlement displacement observation points are arranged on the periphery of the foundation pit, with a total of 10 observation points numbered VS2 ~ VS11. Among them, 4 settlement observation points are arranged on one side of the tunnel, and they are arranged on the crosswalk directly above the tunnel (the crosswalk near the side of the foundation pit). The plane layout of observation points is shown in Fig. 9.3.

9.2 Establishment of Finite Element Model 9.2.1 Basic Assumptions for Model Establishment Midas/GTSNX finite element software is used for numerical simulation. In order to ensure the accuracy of the finite element analysis model in the process of analysis and calculation, the software numerical simulation process should restore the various working conditions of the project site to the maximum extent. However, because of the complexity of the project construction site, especial geological conditions and the construction of the working condition of the error of construction, the finite

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9 Impact of High-Rise Construction on Adjacent Existing Tunnels

Fig. 9.3 Layout diagram of foundation pit monitoring points

element software in finite element simulation of a specific project is difficult to exactly simulate the scene of the actual situation, so in this case the actual situation of construction site must be properly simplified. This section simplifies the actual project as follows: 1. After consulting the exploration data, it is found that the terrain in the excavation area of the newly built foundation pit is relatively flat on the whole. Based on this, the strata in the model are appropriately simplified during the finite element modeling. It is assumed that the surface and all soil layers are homogeneous and horizontal. 2. According to the investigation of groundwater in the site, it can be seen that the type of groundwater in the site is mainly fissure water accompanied by pore water. The numerical simulation model in this section does not consider the influence of groundwater changes on the tunnel. 3. In the modeling process of numerical simulation, mesh encryption is made for the excavation part of the foundation pit, the influence range of the excavation of the foundation pit, the foundation part of the new and existing buildings, the tunnel and the tunnel lining part.

9.2 Establishment of Finite Element Model

189

9.2.2 Selection of Parameters of Each Material Unit in the Model and Setting of Boundary Conditions 1. Selection of constitutive model in the model Linear elasticity model and Mohr–Coulomb model were selected according to the characteristics of the software and the materials used. Mohr–Coulomb model was adopted for the geotechnical mass in the model, while linear elastic model was adopted for other structural units in the model, such as tunnel lining unit, underground diaphragm wall unit, basement slab, anchor bolt unit, floor slab, column, shear wall of main structure, etc. Linear elastic model is one of the simplest constitutive models in MIDAS/GTSNX, and it is a constitutive model in which stress and stress become proportional. The constitutive model means that the material type is an isotropic continuum with linear stress–strain characteristics. The main parameters are E (elastic modulus), μ(Poisson’s ratio), γ (severity). The failure criterion of Mohr–Coulomb model is simple and accurate, which is widely used in rock and soil mass materials. When the stress of the material is less than the yield strength of the material itself, the material only produces elastic deformation. When the stress of the material itself is greater than the yield strength, the material will undergo irreversible plastic deformation. In this stage, the amount of plastic deformation of the material increases with the increase of the stress, until the final failure. The basic parameters of Mohr–Coulomb model are E (elastic modulus), μ (Poisson’s ratio), γ (severe), C (cohesion) and ϕ (internal friction Angle). 2. Determine the types of structural units (1) Geotechnical unit The 3D solid unit in the software is selected as the rock and soil mass unit. The entity unit can be composed of four nodes, six nodes, or eight nodes. The solid element selected in this study is a hexahedral element with 8 nodes. Each node of the element has linear displacement degrees of freedom in 3 directions, and the simulation results are in good agreement with the actual results. (2) Tunnel lining, floor wall, floor slab and shear wall The above structural materials in the model are all 2D plate elements. The plate element composed of 3–4 nodes in the same plane can be used to solve the structural problems of plane tension, plane compression, plane shearing, bending and shearing along the thickness direction of the plate in engineering. Can be used to simulate shotcrete, lining, etc. The unit has translational DOF in three directions and rotational DOF in X and Y directions at each stage. (3) Column unit The element type used in the main structure column element is 1D beam element. It is composed of two nodes and belongs to the beam element with equal section. The

190

9 Impact of High-Rise Construction on Adjacent Existing Tunnels

Table 9.3 The values of each material parameter in the model Materials

γ (kN/m3 )

E(MPa)

C(kPa)

μ

ϕ(◦ )

Miscellaneous fill

17.5

10

10

0.35

10

Silty clay

19.3

15

25

0.33

22

Granite

23.5

500

85

0.23

32

Sprayed concrete

24.5

2.8 × 104

–

0.2

–

The second line

25

3.15 ×

–

0.3

–

Rock bolt

25

2 × 105

–

0.3

–

104

beam element is generally used in the material section size compared with the larger length of the component. Each node of the element has three displacement degrees of freedom and three rotational degrees of freedom. 3. Set boundary conditions and select material parameters In order to ensure the accuracy of simulation, the size of this model is consistent with that of the engineering site. Considering that the effect will have a certain influence on the simulation results, combining with the actual size of the new building, the length × width × height of the model is selected as 200 m × 240 m × 56 m after comprehensive consideration. Based on this, the boundary conditions of the model are set as follows: horizontal displacement constraints are added to the side of the model, free boundary is added to the top of the model, and vertical displacement constraints are added to the bottom of the model (Table 9.3).

9.2.3 Setting of Load Conditions of the Model The loading of this model is mainly divided into three parts. The first part is the dead weight load of rock and soil mass. The second part is the building loading of the existing building and the new building, in which the existing building is loaded once and the new building is loaded eight times successively. The third part is the building wind load, the size of the wind load according to the code calculation. According to the provisions on building wind load in Code for Load of Building Structures GB50009–2012, when calculating the main structure of a building, the standard value of wind load perpendicular to the surface of a new building is calculated as follows: ωk = βz μs μz ω0 in the formula ωk —characteristi cvalue o fwindload (k N /m 2 ); βz —Wind vibration coefficient at height z; μs —shape factor of wind load; μz —Change coefficient of wind pressure height;

(9.1)

9.2 Establishment of Finite Element Model

191

ω0 —Basic local wind pressure (kN/m2 ). (1) Calculation of basic wind pressure According to the regulations, the basic wind pressure should be the wind pressure in the 50-year return period determined according to the methods specified in the regulations, which should be less than 0.3 kN/m2 . For high-rise buildings, highrise structures and other structures that are sensitive to wind load, the basic wind pressure value selected during calculation should be increased appropriately, and should conform to the requirements of the relevant building structure codes. The designed service life of the new building in this model is 70 years, and the basic wind pressure is set as 0.7 kPa according to the return period of 100 years in Qingdao area according to the reference specification. Since the value of the basic wind pressure is calculated at the standard height of 10 m from the ground, for the basic wind pressure of other heights, the following formula can be used for conversion: ωa (z) = ω0a

(

z zs

)2α (9.2)

in the formula, ωa (z)—Conversion value of wind pressure at height z above the ground (kPa); ω0a —Basic wind pressure at 10 m above the ground (kPa); 2α—Wind pressure conversion factor. (2) Selection of wind pressure height change coefficient The selection of variation coefficient of wind pressure height should be determined by the type of surface roughness of the ground in the field. The surface roughness can be divided into four categories: A, B, C and D. In this example, based on the surface roughness of class C (i.e., the city with dense buildings), the change coefficient of wind pressure height is calculated according to the regulations. (3) The value of wind load shape coefficient Referred to the relevant tables in the specification, the size coefficient of stroke load in this case is as follows: + 0.8 for the windward side and −0.55 for the leeward side. (4) Calculation of wind vibration coefficient Wind vibration coefficient is calculated as follows: βz = 1 +

ϕ1 (z)ξ v μz

(9.3)

in the formula, ξ —Pulsation increase coefficient, check the specification to determine the value; v—The influence coefficient of pulsation is determined according to the height, height-width ratio of the structure and the surface roughness of class C;

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9 Impact of High-Rise Construction on Adjacent Existing Tunnels

Table 9.4 Calculated values of wind load building height (m)

fundamental wind pressure (kPa)

wind pressure gust response Windward height change coefficient (βz ) load (kPa) coefficient (μz )

Leeward load (kPa)

12

0.65

0.74

1.12

0.43

0.30

24

0.85

0.90

1.20

0.73

0.50

36

1.00

1.08

1.25

1.08

0.74

48

1.12

1.23

1.30

1.43

0.98

60

1.23

1.35

1.34

1.78

1.22

72

1.32

1.47

1.37

2.13

1.46

84

1.41

1.57

1.41

2.50

1.72

96

1.48

1.67

1.44

2.85

1.96

ϕ1 (z)—The first mode function of the structure. For the convenience of calculation, this model takes the four-story building height (12 m) as a calculation unit to calculate the wind load, and carries out linear interpolation for the other heights. To sum up, the calculation results of wind load are shown in Table 9.4.

9.2.4 Setting of Model Simulation Conditions There are mainly four working conditions in this model, The first working condition analyzes the influence of excavation unloading on adjacent existing tunnels; In the second case, the influence of the new building loading on the adjacent existing tunnel is analyzed; In the third case, the influence of the new building on the adjacent existing tunnel under wind load is analyzed; The fourth working condition analyzes the influence of new high-rise building on the tunnel under different building parameters. The first working condition: the effect of excavation unloading on the adjacent existing tunnel. In this working condition, the ground stress is calculated under the original stratum condition of the model. After the initial ground stress is calculated, the displacement is cleared, and then the tunnel excavation and the excavation of the foundation pit of the new building are carried out. The second working condition: under the condition that the excavation in the first working condition is completed, the construction of the building basement is carried out. After the basement construction is completed, the ground displacement is cleared. At this time, the ground stress condition is taken as the initial condition of the second working condition, and the building is loaded on this basis. In the construction of new buildings, the building loading process is simulated with every four floors as a construction stage, a total of eight construction stages.

9.3 Analysis of the Influence of Excavation Unloading on Tunnel

193

Third working condition: Analysis of influence of new building on adjacent existing tunnel under wind load. Qingdao area belongs to the temperate monsoon climate, its wind direction has obvious change by the seasonal influence, spring and summer mostly east south wind and south wind, autumn and winter mostly northwest wind and north wind, the average annual wind speed is 5.30 m/s, the maximum instantaneous wind speed is 44.20 m/s. Since the new building is located on the south side of the tunnel, the influence of north and south winds is mainly considered. In addition, due to the symmetry of the east–west direction, only the easterly wind load was used for the study. The fourth working condition: change the horizontal distance between the building and the tunnel, building height and other original building parameters, and analyze the impact of high-rise building on the tunnel.

9.2.5 MIDAS/GTS NX Model View The model view is shown in Figs. 9.4 , 9.5 and 9.6.

9.3 Analysis of the Influence of Excavation Unloading on Tunnel By comparing and analyzing the monitoring results of foundation pit with the results of numerical simulation, this section verifies the rationality of the values of rock and soil mass parameters, the setting of constraint conditions, the load and the setting of construction conditions in the model, and meanwhile analyzes the deformation characteristics of the tunnel under the action of foundation pit excavation and unloading. Fig. 9.4 Overall view of the model

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9 Impact of High-Rise Construction on Adjacent Existing Tunnels

Fig. 9.5 Tunnel lining model view

Fig. 9.6 Diaphragm wall view of new building

9.3.1 Analysis of Monitoring Results of Excavation Unloading of Foundation Pit Figures 9.7, 9.8 and 9.9 show the relation diagram of displacement of each monitoring point with time in the process of foundation pit excavation. Considering that the excavation of the foundation pit of the new building will affect the existing adjacent tunnels, each monitoring point near the tunnel side is selected for analysis. The selection points of horizontal and vertical displacements on the top of the foundation pit are the monitoring points of HV10 ~ HV14, and the selection points of the observation points of surrounding surface settlement are the observation points of VS6 ~ VS9. About one month before the excavation of the foundation pit, the corresponding observation points around the foundation pit should be arranged and monitored. According to above time–displacement curve change: in the new buildings in the process of excavation, the horizontal displacement of foundation pit slope top spots appeared to foundation pit side displacement, the displacement value as the

9.3 Analysis of the Influence of Excavation Unloading on Tunnel

195

Fig. 9.7 Time-displacement variation diagram of horizontal displacement at the top of foundation pit slope

Fig. 9.8 Time-displacement variation diagram of vertical displacement at the top of foundation pit slope

Fig. 9.9 Time-settlement displacement variation diagram of crosswalk observation points above the tunnel

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foundation pit excavation is gradually increasing, the change of displacement rate of excavation process comes up first increases then decreases; the change rule of When the excavation of the foundation pit is completed, the horizontal displacement at the top of the slope gradually tends to be stable, and the observed horizontal displacement at the observation point in the middle of the foundation pit is obviously greater than that at the edge of the foundation pit The observed value of the top horizontal displacement appears at the observation point HV12 located in the middle of the foundation pit, and the maximum value is about 6.9 m.

9.3.2 Analysis of Excavation Unloading Numerical Simulation Results Figure 9.10 shows the horizontal displacement and vertical displacement cloud maps of the stratum after the completion of foundation pit excavation. It can be seen from the figure that, after the completion of the excavation of the foundation pit, the side wall of the foundation pit shifted towards the inside of the foundation pit due to excavation unloading, while the soil at the bottom of the pit had a slight uplift displacement. The horizontal displacement of tunnel to the side of the foundation pit is caused by the displacement of soil mass. Through the extraction and analysis of the numerical results, it can be seen that in the soil of the foundation pit near the side of the tunnel, the maximum vertical displacement of the top of the foundation pit slope is 3.05 mm, which occurs at the observation point in the middle of the foundation pit. The maximum horizontal displacement of the slope top of the foundation pit is 5.32 mm, and the position appears at the monitoring point in the middle of the foundation pit. To sum up, by comparing the measured data of foundation pit with the results of numerical simulation, it is found that the numerical simulation results are close to the measured results, indicating that the values of rock and soil mass parameters, the setting of constraint conditions, the setting of load and the setting of construction conditions in the model are reasonable. In the subsequent analysis and calculation,

Fig. 9.10 Displacement cloud map after completion of foundation pit excavation a vertical; b level

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the parameters, constraint conditions, Mohr–Coulomb constitutive model selection, mesh division, optimization, load type and working conditions of the model can be adopted, which lays a foundation for ensuring that the model simulates the loading process of new buildings and the loading process of wind load.

9.3.3 Analysis of the Impact of Excavation Unloading on Adjacent Tunnels 1. Displacement field analysis after completion of foundation pit construction The A-B section in Fig. 9.3 is taken as the research object to analyze the influence of foundation pit excavation on the tunnel. Since this section is located in the middle center of the tunnel and foundation pit, the calculation results of the tunnel section with y = 100 m are extracted from the model for analysis. The monitoring points of the tunnel section are arranged as follows: the number of the monitoring points of the vault settlement and the monitoring points of the tunnel tunnel circumferential convergence deformation is 1, 2, 3, 4 and 5 from left to right, and the number of the observation points of the bottom settlement is 6, 7, 8 and 9 from right to left. The vertical displacement data of section y = 100 m is extracted to obtain the displacement curve as shown in Fig. 9.11. Through the extraction of the calculated data of tunnel section, it is found that with the excavation of the tunnel, the rock mass around the tunnel has a convergence displacement towards the inside of the tunnel. According to the monitoring points 1 and 5, the maximum convergence of the tunnel in the horizontal direction is 4.84 mm. According to the monitoring point 3, the maximum settlement of tunnel vault is 11.5 mm after the completion of tunnel excavation. According to the monitoring point 8, the maximum uplift of the tunnel arch bottom is 11.83 mm. Data and the excavation of tunnel excavation is completed after the completion of the data analysis and comparison, in tunnel excavation is completed the headroom convergence

Fig. 9.11 Vertical displacement curve at y = 100 m: a observation points around the tunnel; b the bottom of the arch

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deformation at the upper end of the basic with the excavation of foundation pit, the change of the clearance of the tunnel convergence deformation quantity, namely the process of foundation pit excavation of tunnel shape variation, namely the process of tunnel excavation clearance displacement of basic no shadow Ring. By comparing and analyzing the overall vertical displacement of the tunnel before and after the excavation of the foundation pit in Fig. 9.11, it can be found that the vertical displacement around the tunnel after the excavation of the foundation pit is less than that before the excavation, and the vertical displacement at the bottom of the arch is greater than that before the excavation, indicating that the tunnel is lifted as a whole along with the excavation of the foundation pit, and the closer the excavation is to the foundation pit, the more displacement is lifted. According to the empirical calculation, the radius of curvature of vertical deformation in this case is 530,296 m, greater than 15,000 m, which meets the requirements of relevant tunnel specifications. Can be seen from Fig. 9.12, at the end of the foundation pit engineering construction, tunnel produced to the side of the horizontal displacement of foundation pit, near the side of foundation pit monitoring of horizontal displacement value is slightly larger than far away from the side of foundation pit monitoring of horizontal displacement value, in the process of foundation pit excavation, the tunnel to the horizontal displacement of foundation pit side average of 0.47 mm. 2. Stress field analysis of tunnel lining after foundation pit construction The lining of the tunnel is selected as the research object to analyze the influence of the excavation process of the foundation pit of the new building on the adjacent existing tunnel. After completion of foundation pit construction, the stress nephogram of surrounding strata is shown in Fig. 9.13. The shear stress force nephogram of tunnel lining is shown in Fig. 9.14. As can be seen from the cloud picture, with the release of the foundation pit of the new building, the largest release area is the vault of the tunnel, as shown in Interpretation 9–14 at the arch foot. As can be seen from the cloud image, along with the excavation process of the foundation pit of the new building,

Fig. 9.12 Horizontal displacement curve at y = 100 m: a observation points around the tunnel; b the bottom of the arch

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Fig. 9.13 Stress nephogram of surrounding strata after completion of foundation pit construction

Fig. 9.14 Cloud diagram of shear stress and principal stress of tunnel after completion of foundation pit construction: a shear stress nephogram; b primary stress nephogram

the surrounding rock stress is released. The biggest release area is the vault of the tunnel, and the release stress is relatively small at the arch foot. The maximum stress of the arch foot near the foundation pit of the building is 0.6 MPa. As can be seen from Fig. 9.14, after the completion of foundation pit construction, the maximum shear stress on the tunnel is 0.7 MPa. The maximum internal force of the tunnel is 0.23 MPa, which is less than the design allowable value of 2.2 MPa for C35 concrete. In this case, the tunnel lining will not produce cracks larger than 0.2 mm in width, so the tunnel is less affected by the construction of the newly built foundation pit, and the tunnel is in a relatively stable state. From the above analysis, it can be concluded that in the process of excavation of foundation pit of new building, the stress release of surrounding rock and soil mass is caused by excavation unloading, but the stress release is uneven, the closer to the foundation pit, the greater the stress release is. Meanwhile, the stress release of vault is greater than that of arch foot. According to the numerical simulation results of the newly built foundation pit of this project, after the completion of the foundation pit excavation, the stress indexes of the foundation pit and tunnel do not exceed the

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design allowable, so it can be concluded that the tunnel is still in a safe state under the influence of foundation pit excavation of the new building.

9.4 Impact Analysis of New Building Loading on Adjacent Existing Tunnels 9.4.1 Deformation Analysis of Surrounding Strata in the Loading Process of New High-Rise Buildings The surrounding stratum deformation nephogram of the new building in the process of construction and loading is shown in Fig. 9.15. As can be seen from the cloud image, the maximum settlement of the surrounding strata is 10.9 mm, and the maximum displacement of the horizontal displacement is 0.89 mm. The horizontal displacement of the stratum is far less than the settlement of the stratum. In the process of new building loading, the deformation of surrounding strata is mainly the subsidence of strata. In order to further determine the settlement range, three different horizontal sections are taken to analyze the settlement of the surrounding strata. Horizontal Sect. 9.1 is the surface of the surrounding strata, horizontal Sect. 9.2 is the section at z = −3 m, and horizontal Sect. 9.3 is the foundation bottom of the new building. The settlement displacement cloud diagrams of the three sections are shown in Figs. 9.16, 9.17and 9.18. From the perspective of the overall displacement nephogram of three horizontal section, in the new buildings in the process of loading, surrounding strata subsidence areas, mainly in new building construction, and the biggest place located at the base of the building foundation settlement and settlement appear from the middle to the law of diminishing, and distribution is symmetrical about the center of the subsidence area. The area where the existing adjacent tunnels are located is basically within the influence range of the subsidence area.

Fig. 9.15 Cloud map of subsidence and horizontal displacement of surrounding strata: a subsidence cloud map; b horizontal displacement nephogram

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Fig. 9.16 Surface subsidence displacement cloud map

Fig. 9.17 Settlement displacement cloud map at z = −3 m section

Comparing the displacement cloud images of subsidence, it is found that the horizontal displacement is smaller than the settlement, and the maximum displacement of the horizontal displacement on the side near the tunnel is 0.76 mm. Meanwhile, the maximum horizontal displacement on the other side is 0.89 mm, and the maximum displacement is located in the basement area outside the main building. This is mainly due to the loading of new buildings, resulting in the surrounding strata to the main settlement of the displacement of the area. Figure 9.19 shows the maximum settlement curve of the stratum in the process of building loading. Each point on the curve is taken from the point at which the stratum has the maximum settlement in the process of building loading. The range taken extends 50 m from the settlement center to both sides respectively.

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Fig. 9.18 Cloud map of settlement displacement of foundation bottom

Fig. 9.19 Settlement of surface of ground

As can be seen from Fig. 9.19, in the process of extending from the settlement center to the left and right sides, the settlement amount on the left and right sides is obviously different. The settlement amount on the right side, which is close to the tunnel, is significantly smaller than that on the side far away from the tunnel. There are two main reasons for this phenomenon. First, the building foundation of the new building is far away from the tunnel, and the main settlement area occurs within the foundation range of the new building, so the impact on this area is small. Second, there is the influence of tunnel stiffness. Since the tunnel already exists before the construction of new buildings, in the process of building loading, the stiffness of the

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tunnel itself and the supporting structure will strengthen the overall stiffness of the surrounding soil, thus leading to a relatively small settlement. According to the above analysis, in order to protect the operation safety of the tunnel, the foundation of the new building should be kept away from the direction of the tunnel as far as possible when the new building is built around the existing nearby tunnel. In addition, as can be seen from the formation of the subsidence curve, from the expansion of the settlement center to the left and right sides of the distance up to 50 m, the formation of the vertical displacement is within 1 mm, can think of, this example engineering in the new building in the process of loading, caused by building loading the influence of building foundation settlement roughly within the scope of construction about 50 m on both sides.

9.4.2 Deformation Analysis of Adjacent Tunnels in the Loading Process of New High-Rise Buildings According to the analysis in Sect. 9.4.1, in the process of construction loading of a new building, the strata around the building may produce vertical displacement and horizontal displacement under the action of load. Drived by the surrounding strata, the existing adjacent tunnels will also have corresponding additional displacement. According to the conclusion in the previous section, since the stiffness of the tunnel itself is greater than that of the surrounding soil, the additional displacement and deformation value under the influence of the surrounding soil should be less than the corresponding deformation value of the rock and soil mass. In addition, due to the influence of ground deformation law, the main deformation of tunnel during the loading process of new building should be vertical settlement, and the horizontal displacement is smaller than the settlement. Considering the complex interaction between rock and soil mass and underground structure, from the perspective of research practicality, the tunnel lining structure is selected as the research object, and the deformation law of tunnel lining in the loading process of new building is mainly analyzed. The deformation is mainly the settlement deformation and horizontal displacement deformation of tunnel lining. 1. Analysis of the influence of loading process on tunnel settlement Figures 9.20 and 9.21 show the settlement displacement nephogram of the tunnel in the loading process of construction and the effect nephogram after magnifying the final deformation. As can be seen from Fig. 9.20, with the construction loading process of the new building, the settlement of the tunnel gradually increases. The maximum settlement occurs after the eighth construction loading, and the value of the maximum settlement is 1.92 mm, located at the tunnel arch near the side of the foundation pit of the new building. From the final deformation of the tunnel, the settlement of the side near the foundation pit of the new building is greater than that of the other side. In the direction

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Fig. 9.20 Cloud image of tunnel settlement displacement in the process of building loading: a first building loading; b second building loading; c third building loading; d fourth building loading; e fifth building loading; f the sixth building loading; g the seventh building loading; h eighth building load

of the longitudinal section of the tunnel, the tunnel settlement shows a deformation law of gradual decrease from the middle to both ends. The middle settlement area is the main area where the tunnel vertical settlement occurs, and the corresponding location is the construction area of the new building (Fig. 9.21). The following mainly analyzes the settlement and deformation law of the tunnel in the loading process of the new building from the cross-section direction and the longitudinal section direction.

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Fig. 9.21 Enlarged rendering of tunnel final deformation

(1) Analysis of settlement deformation along the longitudinal direction of the tunnel According to the results of simulation analysis, the tunnel settlement deformation along the longitudinal direction of the tunnel mainly occurs in the construction area of new buildings, and the maximum settlement location is basically located in the tunnel arch waist. However, the study of the settlement deformation along the longitudinal direction of the tunnel can not only take the tunnel arch waist as the reference basis, so in this section, four key positions of the tunnel vault, the arch bottom and the left and right arch waist are selected as the basic monitoring points of the tunnel settlement deformation. On this basis, the subsidence deformation along the longitudinal direction of the tunnel is analyzed. X axis is taken along the longitudinal section of the tunnel, and Y axis is taken vertically. The coordinate origin is selected at the midpoint of the longitudinal length of the tunnel. In the above coordinate system, the model calculation results of four basic monitoring points of tunnel vault, arch bottom and right and left arch waist are extracted. The settlement curves of each monitoring point are shown in Figs. 9.22, 9.23, 9.24 and 9.25. From Figs. 9.22, 9.23, 9.24 and 9.25, it can be seen that the settlement of each part of the tunnel is symmetrically distributed about the middle point of the tunnel. The center of the tunnel is the place where the maximum settlement is, and the settlement gradually decreases to both sides. This indicates that in the loading process of the new building, the influence range on the longitudinal direction of the tunnel is about 70 m from the tunnel center to both sides. When the distance from the center of the tunnel is more than 70 m, the arch bottom, vault and left and right waist of the tunnel all have different amplitude of lifting, but the displacement of lifting is small and can be basically ignored. By comparing the settlement between the vault and the bottom of the tunnel, it is found that there is little difference between the settlement between the vault and the bottom of the tunnel, which indicates that the overall settlement in the longitudinal direction of the tunnel is more uniform. However, compared with the settlement of the left and right arches, it is found that the settlement of the left arches is obviously greater than that of the right arches, and there is an obvious difference between the two. The reason is that the left arched waist is closer to the new building and is

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Fig. 9.22 Settlement curve of tunnel arch bottom

Fig. 9.23 Settlement curve of tunnel vault

greatly affected by the loading process of the new building. The obvious differential settlement between the right and left waist indicates that there is a certain degree of uneven settlement in the horizontal direction of the tunnel. The existence of this kind of uneven settlement is disadvantageous to the operation of subway tunnel. (2) Analysis of settlement deformation along the cross-section direction of the tunnel For the settlement and deformation analysis in the cross-section direction of the tunnel, we still choose the four key positions of the tunnel arch bottom, vault, left

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Fig. 9.24 Settlement curve of right arch waist of tunnel

Fig. 9.25 Settlement curve of tunnel left arch waist

arch waist and right arch waist as the basic monitoring points for the settlement and deformation of the tunnel. The section studied is the central section of the tunnel, that is, the maximum section of longitudinal axis settlement. This section mainly studies the settlement variation of four basic monitoring points in the central section of the tunnel during the loading process of the new building. As can be seen from Sect. 9.4.2, the load of the new building is loaded in 8 times, so the loading process of the new building can be divided into 8 stages for study respectively. Each stage is loaded once, and the loading unit of the main building is loaded in every four floors. The calculation results of each basic monitoring point in the central section of the

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tunnel in each construction section are extracted, and the settlement curves of each basic monitoring point are shown in Figs. 9.26, 9.27, 9.28 and 9.29. As can be seen from Figs. 9.26 9.27, 9.28 and 9.29, with the construction loading of new buildings, the settlement of the tunnel’s arch bottom, vault, left arch waist and

Fig. 9.26 Vault settlement at various construction stages

Fig. 9.27 Settlement of arch bottom at various construction stages

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Fig. 9.28 Settlement of left arch waist at each construction stage

Fig. 9.29 Settlement of right arch waist at each construction stage

right arch all increased in a linear pattern. By comparing the settlement curves of the four basic monitoring points above, it can be found that the settlement rates of the four basic monitoring points tend to be the same in the loading process of the new building, which indicates that the settlement of the tunnel is uniform in the loading process of the new building. By comparing the left and right arches, it can be seen

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that the settlement of the left arches is obviously larger than that of the right arches, which is consistent with the settlement law along the longitudinal axis of the tunnel analyzed above. 2. Influence analysis of loading process on horizontal displacement of tunnel The horizontal displacement nephogram of tunnel lining in the loading process of new building is shown in Fig. 9.30. As can be seen from Fig. 9.30, in the loading process of new building, the horizontal displacement of tunnel will increase with the continuous increase of building load. However, compared with the settlement displacement of the tunnel in the process of building loading, the horizontal displacement is relatively small, and the maximum horizontal displacement is 0.87 mm, which appears after the completion of building loading. The above analysis method of tunnel settlement in the process of building loading is adopted, and the following deformation mechanism of tunnel horizontal displacement under building loading is analyzed according to the calculation results of MIDAS/GTSNX numerical model. The following is to analyze the deformation law of the horizontal displacement of the tunnel during the loading process of the new building from the cross-section direction and longitudinal section direction of the tunnel. Analysis of horizontal displacement and deformation along the longitudinal direction of the tunnel. The change analysis of tunnel horizontal displacement in the process of building loading refers to the above analysis method of tunnel settlement. The arch of the tunnel, the arch bottom of the tunnel and the arch waist on the left and right sides of the tunnel are still selected as the basic monitoring points of the horizontal displacement. The selection of coordinate axes is consistent with the selection rules of coordinate axes in settlement analysis above. In this coordinate system, the model calculation results of four monitoring points of tunnel vault, arch bottom and right and left arch waist are extracted. The positive direction of horizontal displacement is taken to be positive on the side near the new building, and negative on the contrary. Horizontal displacement curves of each control point are shown in Figs. 9.31, 9.32, 9.33 and 9.34. As can be seen from the horizontal displacement curves of monitoring points above, in the loading process of new buildings, the horizontal displacement deformation law of the tunnel is consistent with the deformation law of settlement, which gradually decreases from the center of the longitudinal axis of the tunnel to both sides, and its influence range is roughly consistent with the influence range of tunnel settlement. The tunnel as a whole is offset towards the new building. Comparing the horizontal displacement of the tunnel vault and the tunnel bottom, it is found that there is little difference between them, and the horizontal displacement of the tunnel left arch waist is obviously greater than that of the right arch waist. The reasons for this phenomenon are analyzed. Firstly, the left arched waist is close to the newly built building, which is greatly affected by the loading process of the new building. 2 it is because of the tunnel lining concrete materials, its elastic modulus is greater than the elastic modulus of surrounding soils, the settlement of building

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Fig. 9.30 Horizontal displacement of tunnel in the process of building loading: a first building loading; b second building loading; c third building loading; d fourth building loading; e fifth building loading; f the sixth building loading; g the seventh building loading; h eighth building load

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Fig. 9.31 Horizontal displacement curve of tunnel vault

Fig. 9.32 Horizontal displacement curve of tunnel arch bottom

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Fig. 9.33 Horizontal displacement curve of tunnel left arch waist

Fig. 9.34 Horizontal displacement curve of right arch waist of tunnel

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foundation pit in the process of building load is greater than the tunnel subsidence, then will there is a rising displacement of the tunnel, the horizontal displacement and the lift displacement under the influence of common cause on the left side of the horizontal displacement of hance is greater than the right side of the arch. In this case, the tunnel tends to twist to the side of the new building. Analysis of horizontal displacement and deformation along the direction of cross section of tunnel. The results of the model are extracted and analyzed. The maximum horizontal displacement of the tunnel is located in the central section of the tunnel. Four points on the central section of the tunnel, namely, the vault, the bottom of the tunnel and the waist of the tunnel, were taken as the monitoring points of the horizontal displacement. The horizontal displacement of four monitoring points on this section is studied. As can be seen from Sect. 9.4.2, the load of the new building is loaded in 8 times, so the loading process of the new building can be divided into 8 stages for study respectively. Each stage is loaded once, and the loading unit of the main building is loaded in every four floors. The calculation results of each basic monitoring point at the tunnel center section in each construction section are extracted. The horizontal displacement curves of each basic monitoring point are shown in Figs. 9.35, 9.36, 9.37 and 9.38. It can be found from the figure that the four basic monitoring points of horizontal displacement are basically consistent in linear law towards the side of the new building with their change rates.

Fig. 9.35 Horizontal displacement of tunnel vault at each construction stage

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Fig. 9.36 Horizontal displacement of tunnel arch bottom at each construction stage

Fig. 9.37 Horizontal displacement of tunnel left arch waist at each construction stage

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Fig. 9.38 Horizontal displacement of tunnel right arch waist at each construction stage

The phenomenon that the horizontal displacement of the arch waist on the left side of the tunnel is greater than the horizontal displacement of the arch waist on the right side of the tunnel, which causes the tunnel to twist, needs to be explained from the interaction mechanism of the building foundation, the surrounding soil and the tunnel. When new buildings on the upper load in the process of building foundation together with the lower soil subsidence, but with the increase of depth, bottom soil experience on the surrounding soil squeezing effect, under the influence of the surrounding soils will be far away from the foundation displacement deformation, while the upper soil is produced by the soil near the side of the displacement deformation. Therefore, in the process of building loading, the rock and soil mass around the tunnel has a torsion trend, which leads to the torsion trend of the tunnel.

9.5 Influence Analysis of Wind Load on Tunnel After Roof Sealing of New Building The building is located in an area that is windy all the year round and is affected by typhoons or outside typhoons 13 times a year. In spring and summer, the wind is mainly east and south, and in autumn and winter, the wind is mainly west and north. The average annual wind speed is 5.30 m/s, and the maximum instantaneous wind speed can reach 44.20 m/s. Considering the relative position of the new building and

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the existing adjacent tunnel, the north wind, south wind and west wind were selected as the research objects to study the influence of building wind load on the tunnel. Section 9.4 analyzes the deformation law of adjacent tunnels under the load of new buildings. The main content of this section is to compare and analyze the changes of each basic monitoring point of tunnels under wind load and without wind load after the roof sealing of new buildings. The deformation of each basic monitoring point of the tunnel under no wind load adopts the tunnel deformation data after the completion of building loading in the above section.

9.5.1 Analysis of the Impact of Northerly Wind Load on Buildings on Tunnels Through the simulation analysis of the wind load applied to the building and the extraction of calculation results, the tunnel settlement displacement nephogram and horizontal displacement nephogram under the action of north wind load are shown in Figs. 9.39 and 9.40. It can be seen from the displacement cloud map that the displacements of the basic monitoring points of the tunnel have obvious changes under the action of north wind compared with that under the absence of wind. The whole tunnel moves towards the side of the new building. Under the north wind load, the maximum settlement displacement of the tunnel is 0.43 mm, and the maximum horizontal displacement of the new building is 0.24 mm.

Fig. 9.39 Horizontal displacement nephogram of tunnel under northerly wind

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Fig. 9.40 Cloud map of vertical displacement of tunnel under northerly wind

Combined with the displacement cloud map and the data extracted from each basic control point, the changes of tunnel horizontal displacement and settlement displacement under northerly wind load are analyzed in detail below. Variation analysis of tunnel vertical settlement under northerly wind load. Figure 9.41 shows the curve of the settlement data comparison between the monitoring points of tunnel arch bottom and vault under wind and no wind load. Figure 9.42 shows the settlement data comparison curve of the monitoring points of the tunnel’s left and right arch waist under wind and no wind load. As can be seen from the settlement comparison curves of each monitoring point in the tunnel above, under the action of north wind load, the settlement of each monitoring point is greater than that without wind load, which indicates that when the building is subjected to north wind load, the displacement and deformation towards one side of the tunnel are generated. Under this movement trend, the soil between the tunnel and the building will have two kinds of movement trends, one is to the side of the building and the other is to the side of the building. This trend will intensify the torsion of the tunnel during the loading process of the building. Therefore, when the building is subjected to the north wind load, the tunnel torsion tends to be increased, which is not conducive to tunnel deformation and thus affects the safe operation of the tunnel. The monitoring point at the tunnel arch bottom is selected as the research object to study the variation of the settlement difference with or without wind load in the longitudinal axis direction of the tunnel. Figure 9.43 shows the variation of the settlement difference of the tunnel arch bottom along the longitudinal axis of the tunnel. As can be seen from Fig. 9.43, in the direction of the longitudinal axis of the tunnel, the maximum settlement difference at the bottom of the arch of the tunnel is

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Fig. 9.41 Contrast diagram of settlement of arch bottom and vault under north wind/no wind load: a tunnel arches; b tunnel vaults

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Fig. 9.42 Comparison curve of settlement of left and right arch waist under north wind/no wind load: a right arch of the tunnel; b the left arch of the tunnel

0.13 mm, indicating that the settlement difference of the tunnel track also changes significantly, which is detrimental to the safe operation of the subway tunnel. 2. Variation analysis of tunnel horizontal displacement under northerly wind load (Figs. 9.44 and 9.45)

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Fig. 9.43 Settlement difference variation curve of arch bottom along the longitudinal axis of tunnel

As can be seen from the figure, the horizontal displacement of each monitoring point in the tunnel under the action of northerly wind load is greater than that without wind load. This indicates that the tunnel moves laterally to the side of the new building after the northerly wind load is applied to the new building. The maximum variation of its horizontal displacement is 0.24 mm, located at the left arch waist of the tunnel. Compared with the displacement of each monitoring point of the tunnel under no wind load, the horizontal displacement of the tunnel changes greatly when the building is subjected to the north wind load. The cause of tunnel horizontal displacement change is bigger, when the north wind loads on the new buildings, building to leaning on one side of the tunnel, the tilt causes construction upside bias tunnel mobile, building bottom will be produced from the displacement of the tunnel, on the basis of the construction part leads, the tunnel produce the large horizontal displacement.

9.5.2 Analysis of the Influence of South Wind Load on the Building on the Tunnel The results of numerical simulation are extracted, and the tunnel settlement displacement cloud map and horizontal displacement cloud under the southerly wind load are shown in Fig. 9.46.

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Fig. 9.44 Horizontal displacement comparison curve of tunnel arch bottom and vault under the action of north wind/no wind load: a tunnel arch bottom; b tunnel vaults

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Fig. 9.45 Horizontal displacement comparison curve of left and right arch waist in tunnel under north wind/no wind load: a right arch of the tunnel; b the left arch of the tunnel

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Fig. 9.46 Displacement cloud map of the tunnel under southerly wind: a horizontal displacement; b vertical displacement

It can be seen from the displacement cloud map that the displacements of each monitoring point in the tunnel under the action of south wind are more obvious than those under the condition of no wind. The tunnel moves to the side away from the newly built building as a whole. According to the model calculation data extraction, the maximum settlement displacement variation of the tunnel is 0.41 mm and the maximum horizontal displacement variation of the tunnel away from the newly built building is 0.22 mm under the action of south wind load. Combined with the displacement cloud map and the data extracted from each monitoring point, the horizontal displacement and settlement displacement of the tunnel under the southerly wind load are further analyzed in detail. 1. Analysis of the change of tunnel vertical settlement under south wind load Figures 9.47 and 9.48 show the settlement comparison curves of each monitoring point in the tunnel under the action of south wind load and without wind load. Tunnel subsidence contrast curve by above knowable, under the action of wind load, new buildings deviated from the original position, to the side away from the tunnel displacement deformation, the deformation by building foundation to lower soil, on the soil mass on one side of the tunnel due to the lower soil squeezing service function, thus caused the tunnel ceiling displacement change. Under the influence of this change, the settlement of each monitoring point in the tunnel has an obvious trend of decreasing, and the maximum variation of settlement displacement is 0.41 mm, which occurs at the waist of the left arch of the tunnel. This change is very beneficial to the safe operation of the tunnel. The monitoring point at the bottom of the tunnel arch is selected as the research object to study the variation of the settlement difference along the longitudinal axis of the tunnel. Figure 9.49 shows the variation of the settlement difference of the tunnel arch bottom along the longitudinal axis of the tunnel. As can be seen from the figure, in the longitudinal axis direction of the tunnel, the maximum settlement difference at the bottom of the arch of the tunnel is 0.13 mm, indicating that the settlement difference of the tunnel track also changes significantly, which is adverse to the safe operation of the tunnel.

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Fig. 9.47 Contrast curve of tunnel arch bottom and vault settlement under south wind/no wind load: a tunnel arch bottom; b tunnel vaults

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Fig. 9.48 Contrast curve of tunnel left and right arch waist settlement under south wind/no wind load: a right arch of the tunnel; b the left arch of the tunnel

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Fig. 9.49 Settlement difference variation curve of arch bottom along the longitudinal axis of tunnel (Southern wind)

2. Analysis on the change of horizontal displacement of tunnel under southwind load The calculated data of the tunnel horizontal displacement are extracted. Figures 9.50 and 9.51 show the comparison curves of the horizontal displacement of the tunnel under the action of south wind load and without wind load.

Fig. 9.50 Horizontal displacement comparison curve of tunnel arch bottom and vault under south wind/no wind load: a tunnel arches; b tunnel vaults

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Fig. 9.51 Horizontal displacement comparison curve of left and right arch waist in tunnel under south wind/no wind load: a right arch of the tunnel; b the left arch of the tunnel

As can be seen from the figure, the horizontal displacement of each monitoring point in the tunnel under the action of southerly wind load is smaller than that without wind load. This indicates that after the southwind load is applied to the new building, the tunnel moves towards the side away from the new building. The maximum variation of its horizontal displacement is 0.22 mm, located at the left arch waist of the tunnel. This influence can be explained from the perspective of the interaction mechanism between the tunnel and the new building. When the new building is subjected to the southwind load, the building is offset to the side far away from the tunnel, which will generate a thrust on the tunnel and increase the relative distance between them, thus changing the horizontal displacement of the tunnel. Combined with the change law of tunnel settlement under north wind load, it can be seen that under the combined action of horizontal displacement and settlement displacement, the tunnel will produce a reverse torsion trend, which can reduce the torsion effect of the original torsion trend on the tunnel, and is beneficial to the safe operation of the tunnel.

9.5.3 Analysis of the Influence of Westerly Load on the Building on the Tunnel Figure 9.52 shows the settlement displacement nephogram and horizontal displacement nephogram of the tunnel under westerly wind load. Through the data extraction of the numerical simulation results, it is found that under the action of westerly wind load, the tunnel settlement and horizontal displacement are less affected by the action of westerly wind load, and the influence is within the range of −70 to 70 m. Therefore, only the data within the influence range is taken as the research object for analysis and research. Through calculation and data extraction results, it is known that under the action of westerly wind load, the maximum

9.5 Influence Analysis of Wind Load on Tunnel After Roof …

229

Fig. 9.52 Cloud map of overall settlement and horizontal displacement of tunnel under westerly load: a horizontal displacement; b vertical displacement

variation of tunnel settlement is 0.11 mm, and the maximum variation of horizontal displacement is 0.05 mm compared with that under no wind load. It can be seen that the horizontal displacement of the tunnel is almost unaffected under the westerly load, so the next step is only to analyze the settlement of the tunnel. In order to more conveniently and directly analyze the deformation law of the tunnel under the action of westerly wind load, the model results of settlement value are extracted, as shown in Table 9.5. Through the analysis of the extracted settlement data, it can be seen that under the influence of westerly wind load, the tunnel settlement value has changed compared with that without wind load, but the change is not large, and the maximum change of settlement is 0.11 mm. The change rule is that the displacement of the four monitoring points in the positive direction of the longitudinal axis of the tunnel is slightly lifted, while the displacement of the monitoring points in the negative direction of the longitudinal axis of the tunnel is slightly lifted, and the displacement of the monitoring points in the negative direction of the longitudinal axis of the tunnel is almost the same as that of the subsidence. The change of this displacement is distributed symmetrically about the center of the tunnel. There is no displacement redistribution on the longitudinal axis of the tunnel, which is beneficial for deformation monitoring.

9.5.4 Deformation Under Wind Load According to the above calculation of the deformation under different wind loads, when the building is subjected to wind loads from different directions, the impact on the tunnel displacement and deformation is different. In addition, through the analysis of the formation displacement cloud image, it is found that the formation

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Table 9.5 Calculation results of settlement value model Tunnel longitudinal axis (m)

Westerly winds vault

No wind vault

Westerly winds arch bottom

No wind arch bottom

The west wind arches to the left

Arch left without wind

The west wind arches right

No wind right arch

−72

0

0.01

0

0

0

0

0

0

−64

−0.02

−0.01

−0.01

−0.02

−0.07

−0.06

0

0

−56

−0.08

−0.06

−0.04

−0.05

−0.13

−0.11

−0.04

−0.03

−48

−0.17

−0.15

−0.09

−0.11

−0.29

−0.25

−0.08

−0.07

−40

−0.32

−0.28

−0.16

−0.19

−0.55

−0.47

−0.14

−0.12

−32

−0.51

−0.46

−0.27

−0.3

−0.88

−0.79

−0.21

−0.19

−24

−0.73

−0.67

−0.39

−0.42

−1.3

−1.19

−0.28

−0.26

−16

−0.92

−0.87

−0.51

−0.53

−1.67

−1.57

−0.34

−0.33

−8

−1.04

−1

−0.6

−0.62

−1.89

−1.83

−0.38

−0.37

0

−1.1

−1.1

−0.65

−0.65

−1.92

−1.92

−0.39

−0.39

8

−0.98

−1

−0.6

−0.62

−1.77

−1.83

−0.36

−0.37

16

−0.82

−0.87

−0.51

−0.53

−1.46

−1.57

−0.31

−0.33

24

−0.61

−0.67

−0.39

−0.42

−1.08

−1.19

−0.24

−0.26

32

−0.41

−0.46

−0.27

−0.3

−0.7

−0.79

−0.17

−0.19

40

−0.24

−0.28

−0.16

−0.19

−0.4

−0.47

−0.11

−0.12

48

−0.12

−0.15

−0.09

−0.11

−0.21

−0.25

−0.06

−0.07

56

−0.05

−0.06

−0.04

−0.05

−0.09

−0.11

−0.02

−0.03

64

0

−0.02

−0.01

−0.02

−0.05

−0.06

0

0

72

0.01

0.01

0

0

0

0

0

displacement deformation is also affected by wind load to a certain extent. Figure 9.53 shows the displacement cloud map of subsidence deformation under different wind directions.

Fig. 9.53 Cloud map of subsidence displacement under wind load: a subsidence displacement (northerly wind); b formation subsidence displacement (south wind); c ground subsidence displacement (westerly wind)

9.5 Influence Analysis of Wind Load on Tunnel After Roof …

231

As can be seen from the displacement cloud map, when the building is subjected to wind loads from different directions, the settlement field of the ground will change accordingly with the different directions of wind loads. The maximum settlement distribution of the ground settlement field will change obviously with the wind direction change of the displacement position of the wind load. For the stratum soil near the direction of tunnel, its settlement field also has obvious changes in wind direction. Compared with the situation without wind load, the subsidence field of the strata in this area under the action of north wind load increases significantly, while the subsidence field of the strata under the action of south wind load decreases significantly, while the change of west wind is not obvious. By calculation, compared with the settlement under the action of no wind load, the settlement under the action of north wind load increases by 1.3 mm, and the settlement under the action of south wind load The amount of subsidence decreased by 1.3 mm, and the amount of subsidence only increased by 0.3 mm under westerly wind load. When the wind load is not applied, the effect of new high-rise building on the displacement of the existing adjacent tunnel is mainly the vertical settlement, and the change of the horizontal displacement is relatively small. When the wind load is applied to the building, the vertical settlement and horizontal displacement of the adjacent existing tunnel are changed. Figures 9.54 and 9.55 show the settlement difference curves of the horizontal displacement and vertical settlement along the longitudinal axis of the tunnel under different wind loads compared with those under no wind loads. Settlement difference = displacement value under wind load—displacement value without wind load. When the building is subjected to the north wind load, the overall settlement of the tunnel compared with the wind load shows that the maximum value of the overall settlement is 0.43 mm, and the maximum position of settlement occurs at the left arch waist of the tunnel. The maximum settlement occurs at the left arch waist of the tunnel. The horizontal displacement is shown as moving to the side of the building, and the numerical value is shown as increasing. The maximum horizontal displacement variation is 0.24 mm, and the maximum horizontal displacement is located at the left arch of the tunnel. By analyzing the movement trend of settlement

Fig. 9.54 Settlement difference curve of tunnel vault and waist under wind load: a tunnel vaults; b tunnel arches

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9 Impact of High-Rise Construction on Adjacent Existing Tunnels

Fig. 9.55 Curve of horizontal displacement difference of tunnel under wind load

displacement and horizontal displacement, it can be found that when the building is subjected to the north wind load, the tunnel will turn to the side of the building. This trend is disadvantageous to the safe operation of the tunnel. When new south wind loads on buildings, compared with no wind load when the displacement of the tunnel, known under wind load of the tunnel subsidence displacement occurred in horizontal displacement from moving away from the construction side, the biggest change settlement value of 0.41 mm, settling the location of the maximum is located at the left of the tunnel arch waist, the biggest change horizontal displacement value of 0.22 mm, the position is the same as the sedimentation position. Through movement trend analysis of subsidence displacement and horizontal displacement can be found that when building suffered from south wind load, the tunnel will produce contrary to the north wind loads reverse the trend, this trend can reduce the trend of the adverse effect of the tunnel, the trend can reduce the trend of the adverse effect of the tunnel, is good for the safe operation of the tunnel. When the building is subjected to westerly wind load, the settlement displacement and horizontal displacement of the tunnel when there is no wind load are compared. It is found that the influence of westerly wind load on the tunnel is smaller than that of north wind load and south wind load. The influence of westerly wind load on the tunnel is mainly manifested in the settlement displacement of the tunnel, and the maximum variation of the settlement displacement is 0.11 mm. Compared with the horizontal displacement without wind load, the maximum variation of the horizontal displacement is only 0.05 mm. By extracting the calculation data of settlement displacement at each control point of the tunnel under the westerly wind load, the settlement deformation law of the tunnel under the westerly wind load is summarized. Under the action of westerly wind, the control points in the positive direction of the longitudinal axis of the tunnel are slightly lifted up, while the control points in the negative direction are slightly subsided, and the amount of lift and subsidence is

9.6 Influence Analysis of Tunnel Displacement Under Different …

233

almost the same, and the displacement variation presents a symmetrical distribution about the center of the tunnel. In addition, there is no displacement redistribution along the longitudinal axis of the tunnel. To sum up, different wind directions have different effects on the tunnel when acting on the building. The northerly wind load is the most unfavorable to the safe operation of the tunnel. Although the northerly wind load reduces the horizontal displacement of the tunnel, it increases the settlement of the tunnel, and at the same time makes the tunnel turn to the building side. Under the southerly wind load, although the horizontal displacement of the tunnel increases, the torsion trend will be reduced under the combined action of the horizontal displacement and the subsidence movement trend. The westerly load has little effect on the displacement and deformation of the tunnel. The main effect of the westerly load is to change the displacement distribution of the tunnel along the longitudinal axis. Therefore, when a new building is built near the existing tunnel, it is beneficial for the safe operation of the tunnel to choose the structural system less affected by wind load as far as possible.

9.6 Influence Analysis of Tunnel Displacement Under Different Building Parameters and Protection Measures According to the existing three-dimensional model in Sect. 9.2, on the basis of retaining the original basic assumptions, material parameters and boundary conditions, the horizontal distance between the building and the tunnel and the building height and other parameters are modified to conduct numerical simulation. The deformation of tunnel displacement under the influence of different external parameters is analyzed emphatically. The four monitoring points selected in the following sections of this section, namely the tunnel center section, are all the sections with the largest settlement and horizontal displacement values mentioned above.

9.6.1 Impact Analysis of Different Building Heights on Tunnels The height of the building model is 96 m. Considering that the variation law of tunnel settlement and horizontal displacement in each step in the process of building loading is studied in Sects. 9.4 and 9.5, the situation when the building height is lower than 96 m is not studied here. In view of the fact that the project is a high-rise building, this section takes the construction height of 120 m and 150 m respectively for loading research.

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9 Impact of High-Rise Construction on Adjacent Existing Tunnels

Fig. 9.56 Settlement and horizontal displacement of each monitoring point in the tunnel under different building heights: a settlement; b horizontal displacement

Figure 9.56 shows the changes of horizontal displacement and settlement at each basic control point of the tunnel under different building heights. As can be seen from the above graph of the settlement and horizontal displacement of each monitoring point in the tunnel changing with the building height, when the building height changes, the settlement and horizontal displacement of the tunnel change greatly. When the height of the building reaches the maximum simulated height of 150 m, the maximum settlement of the tunnel changes from −1.87 mm at 96 m to −2.92 mm at 150 m, and the maximum horizontal displacement changes from 0.84 to 1.31 mm. Although the settlement and horizontal displacement of the tunnel are still controllable when the building height reaches 150 m, the settlement and horizontal displacement of the tunnel are also increasing with the increase of the building height, which is very unfavorable to the safety of the tunnel structure, and will affect the safe operation of the tunnel in serious cases. Therefore, the influence of building load on the tunnel should be considered when the new high-rise building, especially the super high-rise building, is built near the existing tunnel.

9.6.2 Analysis of the Influence of Different Horizontal Distances Between New Buildings and Adjacent Tunnels on Tunnels In view of the horizontal distanced between the tunnel and the building, four models are divided into four situations when d = 4 m, d = 7 m, d = 10 m and d = 16 m, respectively. The calculation results of the models are extracted, and the variation curves of horizontal displacement and settlement of the tunnel under different horizontal distances are shown in Fig. 9.57. It can be seen from the above displacement curves that the horizontal distance D between the tunnel and the building has a great influence on the displacement of each

9.6 Influence Analysis of Tunnel Displacement Under Different …

235

Fig. 9.57 Settlement and horizontal displacement of each monitoring point in the tunnel at different horizontal distances: a settlement; b horizontal displacement

monitoring point in the tunnel. When the distance d increases from 4 m, the settlement and horizontal displacement of each monitoring point in the tunnel decrease to different degrees. The maximum settlement decreases from −3.63 mm when d = 4 m to −1.57 mm when d = 16 m, and the maximum horizontal displacement decreases from 1.23 mm when d = 4 m to d = 0.76 mm at 16 m. Therefore, when the horizontal distance between the new building and the tunnel value gradually increases, the displacement field of the tunnel presents an overall trend of attenuation.

9.6.3 Protective Measures for Adjacent Tunnels 1. Impact evaluation of foundation pit support on tunnel displacement In order to study whether the foundation pit support will have an impact on the displacement field of adjacent tunnels, other parameters and building structures are retained on the basis of the original model, and the retaining wall and anchor rod of the foundation pit support in the original model are deleted to generate the model P1. Figure 9.58 shows the computed displacement nephogram of Model P1. By comparing the displacement cloud map of the tunnel with the foundation pit support, it is found that the displacement deformation of the tunnel without the foundation pit support is very severe compared with that under the foundation pit support. The maximum settlement of the tunnel increases rapidly from −1.87 to −6.67 mm, and the displacement increases by 257%; The maximum horizontal displacement rapidly increases from 0.84 to 2.91 mm, with an increase of 246%. The rapid increase of this displacement is very disadvantageous to the safe operation of adjacent tunnels.

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9 Impact of High-Rise Construction on Adjacent Existing Tunnels

Fig. 9.58 Cloud map of tunnel settlement and horizontal displacement without foundation pit support: a settlement; b horizontal displacement

It can be seen that when a new building is built around the existing tunnel, the necessary foundation pit support can not only ensure the displacement and deformation of the foundation pit within the allowable range, but also prevent the development and evolution of the tunnel displacement field to some extent. Not considering the influence of underground water level, this study through the known literature review [5], foundation pit support can effectively block of groundwater seepage, under the influence of the block, the soil around the foundation pit of underground water level will rise, known from soil mechanics knowledge, the underground water level below the soil effective stress will change, thus affect the tunnel displacement field changes. If the displacement variation is large, it will affect the safety of the tunnel structural system, and even lead to the failure of the tunnel structural system in serious cases. 2. Protection of tunnel structure by blocking piles Because the elastic modulus of the pile and the stiffness of the pile are larger than that of the soil, the settlement of the soil around the pile top tends to be the same as that of the pile bottom. In the process of construction and loading of new buildings, the settlement of building foundation will cause the change of the displacement field of surrounding soil, which will lead to different displacement changes at different depths under the same projection point in the plane. Generally, the displacement of shallow soil under the foundation is larger, while the displacement of deep soil is smaller. When the influence displacement of building foundation is transferred to the block pile, the displacement of shallow soil and deep soil tends to be the same by taking advantage of the high stiffness of block pile. This method can effectively reduce the subsidence displacement and deformation of the tunnel, thus achieving the purpose of controlling the tunnel deformation. Lin [6] studied the protective effect of blocking piles on tunnel displacement and deformation based on Shanghai Metro Line 1 and Line 2 project. The research shows that the displacement of the tunnel decreases obviously when the block piles are set between the tunnel and the building. Compared with the condition without block piles, the displacement decreases by 10–40%, and the settlement blocking effect is

9.6 Influence Analysis of Tunnel Displacement Under Different …

237

obvious. The maximum curvature of the tunnel also has the similar law with the displacement change. The calculation results show that the maximum curvature of the tunnel and the mean curvature both have different decreasing ranges, and the decreasing range of the maximum curvature is up to 12–35%. Zhai studied and analyzed the block piles from the perspective of numerical simulation, and combined with the value of the block piles in Shanghai area, the protection effect of the block piles in practical engineering was analyzed. The concrete conclusions are as follows: in the process of setting the block pile, only when the length of the block pile reaches a certain depth can it play a role in blocking the deformation of the soil outside the pit and effectively reduce the deformation of the tunnel displacement field; When choosing the block pile, the block pile should have a certain stiffness, and it is suggested to adopt the reinforced concrete structure with greater stiffness. However, when the stiffness of the block pile increases to a certain extent, the blocking effect will become smaller and smaller. When choosing the location of the blocking pile, the better soil layer should be selected so that the blocking effect can achieve the best. In addition, due to the great influence on the surrounding soil in the construction process of the foundation pit, the blocking pile should be constructed first in the construction process to reduce the surrounding soil settlement caused by the construction disturbance of the foundation pit. To sum up, the setting of blocking piles obstructs the displacement propagation from the path of displacement propagation and effectively controls the occurrence of displacement and deformation of the tunnel. Especially for the short side of the building foundation near the tunnel, the operation of setting blocking piles can effectively reduce the displacement variation of the adjacent tunnel and ensure the safe operation of the tunnel. 3. Tracking grouting method Tracking grouting method is a construction method that some solidified slurry is injected into the cracks inside the rock and soil mass, so as to change the physical and mechanical parameters of the rock and soil, so as to meet the engineering requirements. Tracking grouting is a commonly used method to prevent and control strata movement. By grouting, the physical and mechanical parameters of the strata are changed to reduce the displacement of the strata. Tracking grouting method shows excellent flexibility and directness in the application process, and it has good adaptability to the accident. In addition, the tracking grouting method has a lower requirement on the site, and has a price advantage compared with the block pile in the cost. Although it has many advantages, the tracking grouting method is still used as a late compensation method, especially for the formation displacement and deformation caused by building foundation, targeted grouting can only be carried out after the displacement has occurred for a period of time, and the effect of such formation compensation will gradually decrease with the passage of time. 4. Optimize building design According to the study in Sect. 9.4, the horizontal distance between the tunnel and the building has a great influence on the displacement field of the tunnel. The smaller the

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9 Impact of High-Rise Construction on Adjacent Existing Tunnels

horizontal distance between the two, the greater the impact of the tunnel. Specifically, when the horizontal distance between the new building and the tunnel increases gradually from small to large, both the settlement displacement and the horizontal displacement of the tunnel show an overall trend of attenuation. Therefore, when a new high-rise building is built near the existing tunnel, a reasonable design scheme should be selected in advance according to the size of the site. Under the condition of satisfying the main function of the building structure, it should be far away from the tunnel structure as far as possible. In this way, not only can the main function of the building structure not be damaged, but also can ensure the safety of the subway tunnel structure.

9.7 Summary In this chapter, the construction process of a new high-rise building and the influence of wind load on the existing tunnel after roof closure are analyzed by numerical simulation based on a high-rise building project near the connecting end of a tunnel. The conclusions are as follows: 1. The influence of foundation pit excavation on the tunnel Based on the actual project, the three-dimensional finite element model is established, and the calculation of the excavation part is carried out. By comparing the calculation results of the model with the measured results, it can be seen that the numerical calculation results are close to the measured results, indicating that the assignment of geotechnical parameters at this time is reasonable. The influence of foundation pit excavation on the tunnel is analyzed. The results show that with the excavation of foundation pit, the tunnel moves toward the side of foundation pit, and the closer to the side of foundation pit, the greater the horizontal displacement is. The average horizontal distance of the tunnel moving toward the side of foundation pit is 0.47 mm. By comparing the vertical displacements before and after foundation pit excavation, it can be seen that the vertical displacement around the tunnel after foundation pit excavation is less than that before excavation, and the vertical displacement at the bottom of the arch is greater than that before excavation, indicating that the tunnel is lifted as a whole along with the excavation of the foundation pit, and the closer the foundation pit is, the greater the displacement is when it is lifted. According to the empirical calculation, the curvature radius of the vertical deformation in this case is 530296 m > 15,000 m, which meets the requirements of relevant tunnel specifications. 2. Influence of loading of new high-rise buildings on existing tunnels nearby The three-dimensional finite element model is used to calculate the loading stage of building construction. Through the analysis of the loading process of building construction, it is found that the influence of tunnel displacement field is mainly the tunnel settlement, and the horizontal displacement of the tunnel is relatively small.

9.7 Summary

239

The maximum displacement and settlement of the tunnel is 1.92 mm; The maximum settlement is 0.87 mm. The maximum settlement of the stratum around the foundation pit is 10.9 mm, which mainly occurs on the side near the tunnel. By referring to similar projects in relevant literature, it can be seen that the calculation results of finite element can reflect the actual situation of construction more accurately. The analysis results in this chapter show that the influence of construction on the tunnel is within the range required by the code. 3. Influence of wind load on tunnel after roof sealing of new building The displacement and deformation of the tunnel under the action of different wind directions are calculated in the use stage after the building is roofed. The results show that the influence of different wind direction on the tunnel displacement field is different. In addition, the surrounding stratum of the tunnel is also clear. The results show that the tunnel is obviously affected by the building wind load by different wind directions. The analysis results show that the north wind load has a great influence on the settlement displacement of the tunnel, and the horizontal displacement is relatively small, but the horizontal displacement also increases and moves to the side of the building. Through the analysis of the settlement difference on the vertical axis of the tunnel, it can be seen that there is an obvious settlement difference on the vertical axis of the tunnel; Under the action of south wind, both the settlement and the horizontal displacement of the tunnel have corresponding changes. The horizontal displacement shows a trend of moving away from the building. Although the horizontal displacement increases, it is beneficial to the safe operation of the tunnel; Under the action of westerly load, the displacement field of the tunnel changes little, indicating that the influence of building westerly load on the tunnel is small, but under the action of westerly load, The horizontal displacement of the tunnel structure on both sides of the tunnel center moves in the opposite direction. By extracting the numerical simulation results, the maximum settlement displacement of the tunnel under north wind load is increased by 0.41 mm, and the maximum horizontal displacement is increased by 0.24 mm compared with that without wind load; Under the southerly wind load, the maximum settlement displacement of the tunnel changes by 0.41 mm and the maximum horizontal displacement by 0.22 mm compared with that under no wind load; Under the westerly wind load, the maximum settlement displacement of the tunnel changes by 0.11 mm and the maximum horizontal displacement changes by 0.05 mm compared with that under no wind load. 4. Protection measures for tunnels According to the analysis of the displacement field variation of the tunnel with different parameters, in the construction process of the new high-rise building near the tunnel, the horizontal distance between the building and the tunnel, the height of the building, the wind direction of the building will have a greater impact on the displacement field of the tunnel, so the above factors should be taken into account in the design stage.

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Based on the analysis of the results of the numerical model, it is suggested that the distance between the building and the tunnel should be kept above 10 m when new buildings are built around the tunnel, so as to ensure the safe operation of the tunnel. When the site is small or the short side of the building is close to the tunnel, the influence of building height and the setting of blocking piles should be considered in the design. In addition, when the tunnel is in the windward side, the horizontal displacement of the tunnel should be paid more attention in the construction monitoring process. When the tunnel is in the leeward side, the settlement displacement of the tunnel should be paid more attention.

References 1. Lingrong K, Yonggao C, Haibo S (2010) Analysis of influence of foundation pit excavation on adjacent subway deformation. Eng Inv Surveying 6:15–20 2. Xue C (2017) Research on influence of urban high-rise building near subway tunnel construction. J Highw Transp Technol 33(2):70–75 3. Hongwei D, Renpeng C, Yunmin C (2006) Chin J Geotech Eng 28(3):312–316 4. Mr. Qu (2013) Analysis of technical influence of proposed adjacent buildings on existing tunnels. Qingdao Technological University, Qingdao 5. Yongguo L, Zhengmao Z, Guobin L (2001) Constr Technol 32(4):233–234 6. Jiequn Z, Jian J, Xiaolin X (2010) J Undergr Space Eng 6(1):162–166

Appendix A

Anti-analysis program INANA.m clc clear all close all % Measured data of ground subsidence H=13.25 A=6.5 X= [ -12.787 , -7.1 , -3.4 ,0 ,3.17 ,10.63 ] Wi0= [ 0.0053 , 0.039 , 0.0438 , 0.053 , 0.05 , 0.036] %-------------------------------------------------------Range= [ tan ( 10 / 180*pi ), tan ( 80 / 180*pi )0 0.2 ]; %------------------------------------------------------------popsize=50 ; subpopnum=10 ; maxgen=20 ; %------------------------------------------------------------Parameters.H=H ; Parameters.A=A ; Parameters.X=X ; Parameters.Wi0=Wi0 ; [Population0 , F0] =Initialize ( Range , popsize , Parameters ); For i=1 : maxgen [ F1 , I ] =sort ( F0 , ’descend’ ); Population1=Population0 ( I ,:); for j=1 : subpopnum Population2 =Population1 ( j : subpopnum : end ,:); F2=F1 ( j : subpopnum : end ,:); [Population3 , F3] =Cross ( Population2 , F2 , Parameters ); [Population4 , F4] =Mutate ( Population3 , F3 , Range , Parameters ); [Population5 , F5] =Disturb ( Population4 , F4 , Range , Parameters , 5 ); Population0 ( j : subpopnum : end ,:) =Population5 ; F0 ( j : subpopnum : end ,:) =F5 ; end [ fs , i _ max ] =max ( F0 ); tan _ beta=Population0 ( i _ max , 1 ); delta _ A=Population0 ( i _ max , 2 ); © China Architecture Publishing & Media Co., Ltd. 2022 D. Meng et al., Prediction and Control of Interaction Between Ground Building and Tunnel Construction Process, https://doi.org/10.1007/978-981-19-3474-2

241

242

Appendix A

fs=-fs ; disp ([ ’gen=’,num2str ( i ), ’ ,F=’ , num2str ( fs , ’%0.8f’ ), ’ ,tan _ beta=’ ,num2str ( tan _ beta , ’%0.8f’ ), ’ , delta _ A=’ , num2str ( delta _ A , ’%0.8f’ )]); end %------------------------------------------------------------disp ; Population1= [ tan _ beta delta _ A ] [F1 , Wi1 ] =Fitness ( Population1 , Parameters ) %------------------------------------------------------------function[Population1 , F1 ] =Initialize ( Range , popsize , Parameters ) digit=size ( Range , 1 ); Population1=zeros ( popsize , digit ); fori=1 : digit range=Range ( i ,:); Population1 (:, i ) =range ( 1 ) + ( range ( 2 ) range ( 1 )) *rand ( popsize , 1 ); end F1=-Fitness ( Population1 , Parameters ); function[Population2 , F2 ] =Cross ( Population1 , F1 , Parameters ) %------------------------------------------------------------Pc= [ 0.6 , 0.99 ]; [PCross , FCross , I ] =SelfAdaptionCross ( Population1 , F1 , Pc ); Population2=Population1 ; F2=F1 ; c=length ( I )/ 2 ; ifc>0 Par1=PCross ( 1 : 2 : end ,:); Par2=PCross ( 2 : 2 : end ,:); F _ Par1=FCross ( 1 : 2 : end ); F _ Par2=FCross ( 2 : 2 : end ); [ Off1 , F _ Off1 , Off2 , F _ Off2 ] = SubCross1 ( Par1 , F _ Par1 , Par2 , F _ Par2 , Parameters ); F4= [ F _ Par1 , F _ Par2 , F _ Off1 , F _ Off2 ]; [ tmp , I4 ] =sort ( F4 , 2 , ’descend’ ); F _ Off1=tmp (:, 1 ); F _ Off2=tmp (:, 2 ); fori=1 : c tmp4= [ Par1 ( i ,:); Par2 ( i ,:); Off1 ( i ,:); Off2 ( i ,:)]; Off1 ( i ,:) =tmp4 ( I4 ( i , 1 ),:); Off2 ( i ,:) =tmp4 ( I4 ( i , 2 ),:); end Population2 ( I ,:) = [ Off1 ; Off2 ]; F2 ( I ) = [ F _ Off1 ; F _ Off2 ]; end [F2 , I ] =sort ( F2 , ’descend’ ); Population2=Population2 ( I ,:); %---------------------------------------------------------------------------function[PCross , FCross , I ] =SelfAdaptionCross ( Population1 , F1 , Pc0 ) pc1=max ( Pc0 );

Appendix A

243

pc2=min ( Pc0 ); [popsize , digit ] =size ( Population1 ); If mod ( popsize , 2 ) n=popsize-1 ; else n=popsize ; end F0=F1 ( 1 : n ); F0=reshape ( F0 , 2 , n / 2 ); F0=max ( F0 ); f _ max=max ( F1 ); f _ avg=mean ( F1 ); I=find ( F0>f _ avg ); J= [ 1 : n / 2 ] ’ ; J ( I ) = []; Pc=zeros ( 1 , n / 2 ); Pc ( I ) =pc1- ( pc1-pc2 ) * ( F0 ( I ) -f _ avg )/( f _ max-f _ avg ); Pc ( J ) =pc1*ones ( length ( J ), 1 ); %-------------------P=rand ( 1 , n / 2 ); I=find ( PF1 ( i ) Population2 ( i ,:) =Population4 ( i ,:); F2 ( i ) =F4 ( i ); end end [F2 , I ] =sort ( F2 , ’descend’ ); Population2=Population2 ( I ,:); %-------------------------------------If quick>0 P _ max=Population2 ( 1 ,:); F _ max=F2 ( 1 ); n=num ; m=quick ; fori=1 : m P _ max _ array=repmat ( P _ max , n , 1 ); T=1 : num ; For k=1 : n j=T ( k ); range=Range ( j ,:); d=D ( j ); P _ max _ array ( k , j ) =P _ max _ array ( k , j ) +2*d*rand () -d ; P _ max _ array ( k , j ) =max ( range ( 1 ), P _ max _ array ( k , j )); P _ max _ array ( k , j ) =min ( range ( 2 ), P _ max _ array ( k , j )); end F _ max _ Array=-Fitness ( P _ max _ array , Parameters ); [ F1 _ max , i _ max ] =max ( F _ max _ Array ); P1 _ max=P _ max _ array ( i _ max ,:); If (F1 _ max>F _ max ) P _ max=P1 _ max ; F _ max=F1 _ max ; end end Population2 ( 1 ,:) =P _ max ; F2 ( 1 ) =F _ max ; end function[F1 , Wi ] =Fitness ( Population1 , Parameters ) [popsize , digit ] =size ( Population1 ); H=Parameters.H ; A=Parameters.A ; X=Parameters.X ; Wi0=Parameters.Wi0 ; F1=zeros ( popsize , 1 ); Wi=zeros ( popsize , length ( Wi0 )); For i=1 : popsize tan _ beta=Population1 ( i , 1 ); delta _ A=Population1 ( i , 2 ); [ F1 ( i ), Wi ( i ,:)] =FunOptimal ( tan _ beta , delta _ A , H , A , X , Wi0 ); end %-------------------------------------------------------------

Appendix A

245

Function [ f , Wi ] =FunOptimal ( tan _ beta , delta _ A , H , A , X , Wi0 ) Warning off all p=20 ; coordinate=1 ; switch coordinate case1 %------------------------------------------------------------a=H-A / 2 ; b=H+A / 2 ; ETA1=linspace ( a , b , p ); d _ eta1= ( b-a )/( p-1 ); ( =-real ( sqrt (( A / 2+53/ A ).^2- ( H-ETA1A / 2+ ( A / 2+53/ A )).^2 )); d=-c ; Wa=zeros ( 1 , length ( X )); for j=1 : length ( X ) x=X ( j ); Q=zeros ( 1 , p ); for i=1 : p eta1=ETA1 ( i ); F=@ ( xi )tan _ beta/ eta1*exp ( -pi*tan _ beta.^2. / eta1.^2* ( xxi ) .^2 ); Q ( i ) =quad ( F , c ( i ), d ( i )); end Wa ( j ) =sum ( Q ) *d _ eta1 ; end Wa ; %-----------------------------------------------------------e=H- ( A / 2-delta _ A ); f=H+ ( A / 2-delta _ A ); ETA2=linspace ( e , f , p ); d _ eta2= ( f-e )/( p-1 ); g=-real ( sqrt ((( A / 2+53 / A ) -delta _ A ) .^2- ( H-ETA2A / 2+ ( A / 2+53 / A )) .^2 )); h=-g ; Wb=zeros ( 1 , length ( X )); For j=1 : length ( X ) x=X ( j ); Q=zeros ( 1 , p ); For i=1 : p eta2=ETA2 ( i ); F=@ ( xi )tan _ beta/ eta2*exp ( pi*tan _ beta.^2. / eta2.^2* ( x-xi ) .^2 ); Q ( i ) =quad ( F , g ( i ), h ( i )); end Wb ( j ) =sum ( Q ) *d _ eta2 ; end Wb ; %-----------------------------------------------------------Wi=Wa-Wb ; case2

246

Appendix A %--------------------------------------------------------

----Wi=zeros ( 1 , length ( X )); For j=1 : length ( X ) x=X ( j ); F=@ ( r , theta ) tan _ beta. /( r.*cos ( theta ) +H ) .*exp ( pi*tan _ beta.^2. /( r.*cos ( the-ta ) +H ) .^2.* ( xr.*sin ( theta )) .^2 ) .*r ; Wi ( j ) =dblquad ( F , A-delta _ A , A , 0 , 2*pi ); end Wi ; end %------------------------------------------------------------f=sum (( Wi-Wi0 ) .^2 ); function[Population2 , F2 ] =Mutate ( Population1 , F1 , Range , Parameters ); Pm= [ 0.01 , 0.1 ]; [PMutate , FMutate , I ] =SelfAdaptionMutate ( Population1 , F1 , Pm ); m=length ( I ); digit=size ( Population1 , 2 ); Population2=Population1 ; F2=F1 ; [tmp , i max ] =max (F1 ); If m>0 Par=PMutate ; F _ Par=FMutate ; [ Off , F _ Off ] =SubMutate1 ( Par , F _ Par , Range , Parameters ); For i=1 : m If I ( i ) ==i _ max&F _ Par ( i ) >F _ Off ( i ) Off ( i ,:) =Par ( i ,:); F _ Off ( i ) =F _ Par ( i ); end end F2 ( I ) =F _ Off ; Population2 ( I ,:) =Off ; end [F2 , I ] =sort ( F2 , ’descend’ ); Population2=Population2 ( I ,:); %------------------------------------------------------------------------function[PMutate , FMutate , I ] =SelfAdaptionMutate ( Population1 , F1 , Pm0 ) pm1=max ( Pm0 ); pm2=min ( Pm0 ); [popsize , digit ] =size ( Population1 ); f _ max=max ( F1 ); f _ avg=mean ( F1 ); I=find ( F1>f _ avg ); J= [ 1 : popsize ] ’ ; J ( I ) = []; Pm=zeros ( popsize , 1 ); Pm ( I ) =pm1- ( pm1-pm2 ) * ( F1 ( I ) -f _ avg )/( f _ max-f _ avg ); Pm ( J ) =pm1*ones ( length ( J ), 1 );

Appendix A

247

%-------------------------P=rand ( popsize , 1 ); I=find ( P