Geotechnical Characterization, Field Measurement, and Laboratory Testing of Municipal Solid Waste 0784411468, 9780784411469

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Geotechnical Testing, Observation, and Documentation THIRD EDITION

TIM DAVIS

Geotechnical Testing, Observation, and Documentation Third Edition

Other Titles of Interest Geotechnical Baseline Reports for Construction: Suggested Guidelines, 2nd Edition, edited by Randall J. Essex (ASCE/CI 2007). This book examines the role of the geotechnical baseline report (GBR) as a means of allocating and managing subsurface risks associated with subsurface construction. (ISBN 978-0-7844-0930-5) Geotechnical Characterization, Field Measurement, and Laboratory Testing of Municipal Solid Waste, edited by Dimitrios Zekkos, Ph.D. (ASCE/G-I 2010). GSP 209 integrates current knowledge of the properties of municipal solid waste with adequate guidance for researchers and practitioners who work directly with issues related to waste behavior. (ISBN 978-0-7844-1146-9) Sound Geotechnical Research to Practice: Honoring Robert D. Holtz II, edited by Armin W. Stuedlein and Barry R. Christopher. (ASCE/G-I 2013). GSP 230 contains 39 papers on applied geotechnical engineering in soft ground construction, reinforced soils, and fundamental soil behavior presented in honor of Robert D. Holtz. (ISBN 978-0-7844-1277-0) Edenville and Sanford Dam Failures: Field Reconnaissance Report, edited by Daniel Pradel and Adam Lobbestael. (ASCE/G-I 2021). GSP 327 presents the results of on-ground and aerial assessments of the Edenville and Sanford Dam failures of 2020. (ISBN 978-0-7844-1576-4) Remote Sensing for Monitoring Embankments, Dams, and Slopes: Recent Advances, edited by Timothy D. Stark, Thomas Oommen, and Zhangwei Ning. (ASCE/G-I 2021). GSP 322 provides information on selecting and deploying a remote sensing monitoring network to assess the behavior, geometry, and potential risks of EDS movement on people and infrastructure. (ISBN 978-0-7844-1572-6)

Geotechnical Testing, Observation, and Documentation Third Edition

Tim Davis

Published by the American Society of Civil Engineers

Library of Congress Cataloging-in-Publication Data Names: Davis, Tim, author. Title: Geotechnical testing, observation, and documentation / Tim Davis. Description: Third edition. | Reston, Virginia : American Society of Civil Engineers, [2022] | Includes bibliographical references and index. | Summary: “Author Tim Davis senior public works inspector for the Towa of Windsor Engineering Department in Sonoma Country, California, assembled this in-depth field manual for soil technicians, inspectors, and geotechnical engineers for use during the investigation, grading, and construction phases of geotechnical projects”– Provided by publisher. Identifiers: LCCN 2021060255 | ISBN 9780784416044 (paperback) | ISBN 9780784480474 (pdf) Subjects: LCSH: Soils–Testing. | Geotechnical engineering. Classification: LCC TA710.5 .D285 2022 | DDC 624.1/5136–dc23/eng/20220118 LC record available at https://lccn.loc.gov/2021060255 Published by American Society of Civil Engineers 1801 Alexander Bell Drive Reston, Virginia 20191-4382 www.asce.org/bookstore | ascelibrary.org Any statements expressed in these materials are those of the individual authors and do not necessarily represent the views of ASCE, which takes no responsibility for any statement made herein. No reference made in this publication to any specific method, product, process, or service constitutes or implies an endorsement, recommendation, or warranty thereof by ASCE. The materials are for general information only and do not represent a standard of ASCE, nor are they intended as a reference in purchase specifications, contracts, regulations, statutes, or any other legal document. ASCE makes no representation or warranty of any kind, whether express or implied, concerning the accuracy, completeness, suitability, or utility of any information, apparatus, product, or process discussed in this publication, and assumes no liability therefor. The information contained in these materials should not be used without first securing competent advice with respect to its suitability for any general or specific application. Anyone utilizing such information assumes all liability arising from such use, including but not limited to infringement of any patent or patents. ASCE and American Society of Civil Engineers—Registered in US Patent and Trademark Office. Photocopies and permissions. Permission to photocopy or reproduce material from ASCE publications can be requested by sending an email to [email protected] or by locating a title in the ASCE Library (https://ascelibrary.org) and using the “Permissions” link. Errata: Errata, if any, can be found at https://doi.org/10.1061/9780784416044. Copyright © 2022 by the American Society of Civil Engineers. All Rights Reserved. ISBN 978-0-7844-1604-4 (print) ISBN 978-0-7844-8047-4 (PDF) ISBN: 978-0-7844-8421-0 (ePub) Manufactured in the United States of America. 27 26 25 24 23 22

1 2 3 4 5

Contents Foreword, by Mary C. Nodine, P.E., M.ASCE ix Author’s Note

x

Acknowledgments

Chapter 1

xi

Field Soil Classification

2

The Unified Soil Classification System Care in Classification

2

2

Writing Soil Descriptions

3

Using the Field Classification Chart Distinguishing Soil Types

3

5

Discerning Fine Sand from Silt or Clay Determining Silt from Clay Dry Strength

5

5

6

Stickiness Test

6

Dilatancy (Shaking Test) 6 Field Dispersion Test (Settling Time) Recognizing Fill or Natural Soil Composition Porosity Color

7

7

7

7

Quick Reference Tables Chapter 1 Questions

Chapter 2

6

8

12

Exploration and Sampling Methods 16 Boreholes

18

The Standard Penetration Test (SPT) Procedure

18

Sampling with Rings Procedure

21

21

v

18

vi

Contents

Thin-Walled Tube Sampling 23 Procedure

24

Backhoe Trenches

25

Rock Hardness Study Chapter 2 Questions

Chapter 3

26 28

Basic Laboratory Tests

32

Modified Proctor/Maximum Density Test Synopsis of Test Methods Apparatus

34

Procedure

35

Calculations and Plot Sieve Analysis

34

38

38

Apparatus

39

Procedure

39

Calculations 41 Hydrometer Analysis Apparatus

41

Procedure

41

41

Calculations 44 Plastic and Liquid Limits Test 45 Definitions

45

Apparatus

45

Preparation (Dry Method) Procedure

46

46

Plastic Limit

47

Liquid Limit

47

Calculations and Graph Plotting Chapter 3 Questions

Chapter 4

48

50

Field Density Tests

52

Importance of Field Density Tests Planning

52

Curve Sampling

53

Commonly Used Field Density Tests Sand Cone Test Overview Apparatus

54

54 55

Plate and Cone Calibration Procedure

52

57

Calculations 60

55

54

33

vii

Contents

Nuclear Gauge Test 60 Nuclear Gauge Safety Taking a Test

60

62

Nuclear Gauge Test Biases Chapter 4 Questions

Chapter 5

63

64

Jobsite Soil Construction 68 Project Preparation Flatland Projects

68

69

Road Construction

69

Preparation and Compaction Hillside Grading

69

72

Areas of Concern during Hillside Grading 72 Rock Fill (Oversize Material) Placement

74

Observation During Rock Fill Placement

75

Cut, Fill, and Transition Pads Deep Foundations

77

77

Important Areas of Observation Shallow Foundations

Usual Areas of Concern

80

Retaining and Specialty Walls Chapter 5 Questions

Chapter 6

78

79 81

82

Geologic Considerations

86

Geologic Concerns on a Grading Project Recognition and Communication Chapter 6 Questions

Chapter 7

86

89

89

Geotechnical Bits and Pieces 92 Compaction Equipment for General Grading Operations

92

Green Grading for Low Impact Development (LID) 95 Geotechnical Construction Integrated with Green Power Wind Turbines

96

Geothermal Energy

96

Anchored Floating Solar Array Lime Treating

Chapter 8

97

98

Project Management and Preparation 104 Project Preparation Observation

105

Communication Testing

107

107

104

96

viii

Contents

Documentation

110

A Technician’s Steps to Success Chapter 8 Questions

Chapter 9

110

113

Putting It All Together: An Example Project Scenario

116

Site Investigation Initial Site Visit

116 117

Borehole and Trench Logging Laboratory Testing

118

Office Pre-Job Meeting Project Organization

118

119

Example Geotechnical Report Chapter 9 Questions

117

119

143

Chapter 10 Project Site Safety 148 Trench Safety

148

Trench Safety Guidelines

148

OSHA’s Trenching and Excavation Safety Who is a Competent Person? Grading Project Safety Chapter 10 Questions

150

152 153

Appendix A

Example Municipal Standards

Appendix B

Answer Key

Appendix C

Glossary of Geotechnical Related Terms

Index 213 About the Author

219

149

155

169 179

116

Foreword Soil Distance As a young engineer, I spent my days In rain, or sun, or snow, or haze, With micropiles and drilling rigs. Some job sites were small, and some were big, But on each dam, each city block, Every strip mall, I’d take stock With cuttings, sand cones, hammer sounds, Of what was underneath the ground. Color, cohesion, plasticity, Gravel content, auger speed, The silt and sand and I were friends. We had our strifes; I won’t pretend That things were always hunky dory. For example, mandatory Plastic wrap on claystone cores, And one-point proctors were a chore : : : But most days, I’d choose grubby hands Over email’s incessant demands. Years went by, and boring logs Transitioned to a monthly slog Through conference calls, drawings, billing too; Soil and I became one step removed As I delegated all of the sampling and sun — The hard work, yes, but a lot of the fun. The next generation is getting their chance To develop their judgment — that delicate dance

Of making decisions in a world full of gray Required for building in sand, silt, and clay. So, I settle for spending the bulk of my hours Making good use of computing power To visit my project sites virtually, Use lab tests and logs in an effort to “see” What’s under the ground, so I understand The geotechnical challenge I can’t view firsthand. While these tools are useful, I can’t help but compare My connection with soil to a friend who’s not there In my real life, but encased in a box on a screen. We can talk, but we can’t share a hug, or caffeine (Well, you can bring your own but : : : you know what I mean.) Project management first revealed it to me. The pandemic enforced with intensity: Despite our technology’s big bag of tricks, There’s no substitute for a real soil fix. Mary C. Nodine, P.E., M.ASCE

ix

Author’s Note During my many years as a technician and inspector, it has become clear how important, and yet how underestimated these two groups are. It will always be engineers, geologists, and the like, who will lead the way with creative new designs, recommendations, and requirements. However, to test, oversee, and document the implementation of the construction—it continues to be the technicians and inspectors at the forefront. It has been my pleasure and good fortune to have worked with, and learned from, a variety of professionals; from technicians to geotechnical engineers, each unselfishly sharing their knowledge and expertise with me. This book is meant to avail much of that wisdom, along with a taste of my own experience. May it be used as a guide and steppingstone for each of you as you head out into this exciting field, be it daily or nightly, using your skills and resources to navigate through each unique project. Whenever you are asked, share your knowledge; in science, the fear of not knowing―is offset by the freedom to ask. Tim Davis

x

Acknowledgments This book would not have been possible without so many unselfish people sharing their experience in the field of their expertise. It is both humbling and reassuring to have been guided so well. With this book I attempt to pay it forward. The contributors listed herein are only the tip of the iceberg of the multitude of acquaintances who have given me the foundation for a better understanding of geotechnical construction. David McKee, P.E., G.E.; Paul Davis , PG, E.G; Elizabeth Cargay, P.G.; Keith Colorado, P.E., G.E.; Glenn Garland; Dylan Farver, lead project engineer; David R. Dupont, P.E.; Robert D. King, Sr. supervisory tech; Matt Pontoni, lab manager; Gery Anderson, P.E., G.E., E.G., P.G.; Donna Dickert, senior manager, Acquisitions, ASCE; Eric Knapp, NICET 1V tech; Matt Davis, senior systems analyst; Jeff Taluban, EIT, lead inspector; David J. Morrell, P.E., G.E.; Dan E. Davis, author, editor; David H. Lee, P.E., G.E.; Lauren Margaux, writer, editor; Steve Lee, lab manager; Betsy Kulamer, former books director, ASCE; Jonathan Bahr, P.E.; Bethany O’Connor, geotechnical/materials tech: Bruce Gossett, former managing director/publisher, ASCE; Robert Delk, supervisory tech; Ken Godwin, engineer/designer; Steve Hicks, project manager/designer; David Lozano, transportation engineering specialist; Benjamin Ciampa, R.G., geophysics manager; Avram Ninyo, P.E., G.E.; Teresa Sedano, M.A.Ed., copyeditor; Michael Rivera, field and lab supervisor; Michie Gluck, books project manager, ASCE; Dick Walsh, material and soil tech —and to the legion of other friends and professionals who have been so kindhearted to share their hard-earned knowledge, and yet tolerant of my continued badgering and questioning. With special recognition to Mary C. Nodine, P.E., who has shared her poem “Social Distance,” which so aptly articulates the purpose of this book, and profoundly expresses the sentiments of this author.

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1 Field Soil Classification The ability to classify soil accurately in the field is the most basic, yet most important procedure performed during field sampling and observation. Although a lab technician can make a definite classification by use of gradation, plasticity, and other tests, the first soil identification is usually made in the field—often by a field technician, engineer, or geologist. Classification is the primary step during all soil projects. When care is not taken to describe soil properly, all the resulting recommendations may be invalid!

The Unified Soil Classification System The Unified Soil Classification System (USCS) is the most widely adopted and recognized classification system used for engineering purposes. It was developed by Dr. Arthur Casagrande in the early 1940s; and then subsequently adopted by the US Army Corps of Engineers in 1952. ASTM International and other testing standard organizations have incorporated the USCS as well. A modified version of the USCS for easy use during field classification is shown on Chart 1-1.

Care in Classification When classifying soil in the field, it is important to closely observe the material and then give as accurate a written description as possible. When logging boreholes or trenches, or obtaining samples for lab testing, a change in material type can provide valuable information for the project engineer, geologist, or another technician involved later in the project. For example, too often during the rush of picking up a Proctor sample, care is not taken to properly classify the material in the field, making it virtually impossible for another technician to identify and match the same sample for field density test calculations. Along with careful classification, making note of sample location—including whether the sample is native or imported—can also aid in avoiding unnecessary confusion. Even seemingly minor details may be of value. For instance, along with a soil classification, descriptive information such as “well graded” or “gap graded” may assist an engineer in a liquefaction study; describing gravel shape helps a geologist determine how a formation was deposited. Adding detailed information such as micaceous, diatomaceous, gypsiferous, porous, or organic, is also helpful.

2

Chapter 1: Field Soil Classification

Even noting the odor of the soil is beneficial during the grading of a site. For example, a strong sewage odor may indicate a nearby cesspool or septic tank. The odor of decaying material may indicate buried trash, organic debris, or even organic soil (peat, for instance). Any chemical smell should be brought to the attention of the project manager immediately. It is likely that the on-site material will then be sampled for a chemical analysis test to determine the presence of any hazardous materials.

Writing Soil Descriptions A.

Silty f-m SAND (SM), Brn., moist, low to non-plastic, micaceous, native

B.

Organic CLAY (OH), Blue, very moist, highly plastic (fat clay) with an organic odor, native

C.

Sandy Silty f-c GRAVEL (GM), Gray, imported Class 2 aggregate base

To help describe grain size of either sand or gravel, the letters f, m, or c may be used (as indicated in Table 1-4). Borderline or combination symbols should be given to soils that exhibit approximately equal characteristics of two Groups, such as GP/GW, CL/ML, or AF-SM/ML. Notice that in each example the predominant soil type is always in capital letters. When modifying a soil type (examples A and C), only the first letter of the modifier is capitalized. In addition, following the written description, the USCS symbol is included in parentheses. Using the USCS symbol in this manner makes it easier to pick out a soil type when reviewing a field report or lab data by simply scanning for the group symbol. The referenced Chart 1-1 defines the Soil Groups by using the USCS Symbol and a correlating Soil Description. The USCS symbols may be modified in a number of ways by using descriptive terminology, including color, size, odor, plasticity, moisture, and consistency, to name a few. A borderline symbol (SP/SM, CL/CH, SC/SM, etc.) may be used to indicate a soil with approximately equal characteristics of two soil groups.

Using the Field Classification Chart Identify a soil as well-graded if it appears to have substantial amounts of all grain sizes, or as poorly graded if it has an unequal distribution, or as gap graded if one size is missing completely. In the lab a well graded soil may be confirmed by performing a full sieve analysis, and then calculating the “Coefficient of Uniformity” (Cu) and “Coefficient of Curvature” (Cc). The symbol AF, for artificial fill, can be placed before a USCS symbol to identify that the soil is fill, such as: AF-SM, AF-CL, AF-SP, and others. Soil types having between 5% and 12% fines (either estimated in the field or confirmed in the laboratory) should be given a dual classification symbol, such

3

4

Chapter 1: Field Soil Classification

as SP-SM, SP-SC, GP-GM, or GP-GC. CL-ML should be used when the soil has characteristics both of low plastic silt and clay. With the Atterberg Limits Test, the PI and LL of a CL-ML soil will plot in the hatched zone on the Plasticity Chart.

Chart 1-1

Field Unified Soil Classification System

Chapter 1: Field Soil Classification

Dual symbols are helpful: Soils exhibiting approximately equal characteristics of two Groups should be given a borderline symbol, such as GP/GW, SC/SM, AF-CL/ML, CL/CH, or any other borderline combination. A careful field classification may not always “match” the final laboratory classification; however, with care and practice it can be very similar. Chart 1-1 can be used for quick field reference―during sampling, while logging, or when classifying existing site or imported materials.

Distinguishing Soil Types When classifying soil in the field, observing grain size is a good place to begin. Although it is impractical to carry a full set of sieves, the field technician must be able to distinguish the different grain sizes as well as estimate their approximate percentages within the sample. For instance, if the sample is an aggregate base used for road placement, and the material appears to be gray in color and seems to have equal percentages of gravel and sand with no appreciable amounts of fines (silt or clay)—using the USCS—you could simply classify the soil as a Gray Poorly Graded SAND and GRAVEL, SP/GP. However, if it visually appears that there is a smooth range (equal amounts) of either sand or gravel; then a GW or SW symbol should be used. (Chart 1-1). Although it is usually not difficult to distinguish sand from gravel, and gravel from cobbles and boulders, it takes a little more practice and closer observation to recognize fine sand from silt, and silt from clay. The following are some simple field tests to help in the visual classification of fine-grained material.

Discerning Fine Sand from Silt or Clay Take the sample in question and rub it between the palms of your hands—then try to shake off the material by rubbing and patting your hands together. Notice that most of the grains of sand fall off, whereas the finer silt and clay particles will tend to adhere within the fine lines in your palm, leaving a “dirty” appearance (hence giving rise to the terms clean or dirty soils—depending on the amount of fines present). Another way to distinguish fine sand from silt and clay is to simply take a very close look at some of the material. The unaided eye cannot easily see the microscopic silt and clay particles, but the individual sand grains can readily be discerned.

Determining Silt from Clay Since clay particles are finer and tend to bond together tighter than silt particles, there are several easy field procedures to distinguish one from the other. Wetting the sample to varying degrees helps, as described in the following field tests.

5

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Chapter 1: Field Soil Classification

Dry Strength Roll moistened pieces of a sample into a 1/8-in. diameter thread and then let it air dry; next, try to crumble the sample between your fingers. A predominantly silty soil will crumble relatively easily, whereas a more clayey material will be harder to break, thus having a higher dry strength. Some silts, if they are non-plastic, cannot be rolled into a thread, thus exhibiting no dry or plastic strength. Dry strength also gives a rough estimate of plasticity— the more plastic, the higher the dry strength. See the procedure in Chapter 3 for the “plastic limit.”

Stickiness Test Place a pinch of soil on your palm, squirt some water over it, and then mix the water into the soil with your finger (take care not to saturate the soil, just moisten it well). More clayey soils feel stickier, and siltier soils generally have a smooth, soft feel to them.

Dilatancy (Shaking Test) Place a portion of the sample in one hand (palm up) and mix in some water until the soil is putty-like. Then—with your empty hand—firmly pat the edge of your sample hand for 3 to 5 seconds. If the soil is predominantly silty, the water will rise to the surface of the soil (the surface will shine). Then upon squeezing the specimen, the water will disappear back into the sample. This phenomenon is called dilatancy. If the water does not rise through the sample, then the clay dominates. Dilatancy occurs because the saturated silt particles become denser with shaking, whereas the more tightly bonded clay particles do not increase in density when jarred. Clay has little to no permeability; silt is more permeable.

Field Dispersion Test (Settling Time) Take a small representative portion of soil (about half a palmful) and add it to a burette, beaker, or clear drinking glass. Add enough water to cover about three times the height of the loose soil. Stir (or if possible, cover the top and shake it) until the soil is broken up and fully dispersed in the solution. Set the sample down and allow the particles to settle. Generally speaking, the larger diameter particles (sand, then silt) will settle more quickly than the smaller (clay) sized particles. Typically, you will be able to observe the difference in the layered thickness of the sand, silt, and clay in approximately one hour. In very clayey samples, the water may remain clouded with floating clay particles for quite some time. By viewing the stratified layers, one can estimate the percentage of each particle group. The concept of the field dispersion test is very similar to the laboratory hydrometer test. Note: Sometimes you may notice golden flecks of mica still floating in the dispersion glass, along with the clay particles. This is because mica is a light-weight mineral and has flat grains (perfect cleavage) : : : mica

Chapter 1: Field Soil Classification

was one of the minerals considered “fool’s gold”. However, with one easy test—panning for gold—mica would float out of the pan.

Recognizing Fill or Natural Soil During a soil investigation or site grading, the depth and approximate limits of untested fill must be determined so that it can be completely removed before placing additional fill. The distinction between artificial fill and natural soil is best made in the field where it is possible to observe the soils in situ, rather than by looking at a smaller sample in the lab. The unnatural location or shape of the fill mass, or the lack of natural vegetation, may be a clear giveaway that the fill was placed recently (within a few years). However, where artificial fill is believed to be old, it may have characteristics similar to the nearby natural soils and terrain. In this case, certain internal factors should be considered, including soil composition (e.g., the presence of human-placed material), color, and porosity.

Composition This is the most obvious indicator of artificial fill. When any human-placed material is found in the soil layer—such as glass, metal, brick, or other debris—it is fill. When foreign materials are not observed, color and porosity may be determining factors.

Porosity One of the more significant, yet often overlooked, ways of distinguishing fill from natural soil—is soil porosity. A natural, near-surface soil develops a fine network of root holes, cracks, and minute openings (porosity) over time. This porosity may be caused by decaying roots (Figure 1-1), burrowing insects, animals, and certain weathering processes. In contrast, during the placement of engineered fill, heavy grading equipment destroys the natural root holes and openings, then redeposits (compacts) the soil in a denser condition. However, even an old, compacted fill can develop porosity of its own—this happens if it has developed a root system or has become inhabited by insects or rodents over a few decades. Table 1-2 indicates some of the usual observable differences between artificial fill (AF) and natural soil.

Color Making note of a soil color is a good first step. Soil color variations may result from pigmentation and oxidation of minerals, organic content, and the amount of moisture present. Using a color chart (such as Munsell) is beneficial. The color of natural, near-surface soil (“topsoil”) varies greatly from dark brown in vegetated moist climates to light brown or near white in an arid desert

7

8

Chapter 1: Field Soil Classification

Figure 1-1

Porous Soil When porous upper soil is found during a site investigation, it is recommended that they be removed and/or recompacted (see Figure 8-2 Project Data Sheet, “Removal Types”). Porous soil is compressible when loaded, even more compressible when water is added under load. Therefore, if porous soil is left in place during grading, footings or slabs may settle over time.

(carbonate-rich) terrain. The darker soil is mainly the result of high organic content from decayed vegetation. Most natural dark organic-rich soil becomes lighter in color gradually, with increased depth. Color changes throughout natural soils are generally gradational, rather than sudden. When describing a soil in the field, include as much information as possible. The descriptive terminology in the Quick Reference Tables 1-2 through 1-12 provide more complete soil description options.

TABLE 1-2 Quick Reference for Identifying Fill or Natural Soil Indicators

Artificial Fill (AF)

Natural Soil

Soil composition

May include glass, brick, concrete, wire, plastic, or other human debris

Completely free of all cultural or foreign material

Color

Can be mottled or multicolored

Usually consistent coloration, yet may vary with depth

Porosity

May be porous near the natural Non-porous, due to ground surface, have root compaction during systems, and decreasing placement, except for very porosity with depth old fill

9

Chapter 1: Field Soil Classification

TABLE 1-3 Descriptive Terminology for Grain Shape Term

Causation

Shape

Angular

Fractured by some weathering action, all edges sharp

Sub-angular

Fractured, some smoothed edges from transportation

Sub-round

Generally round, all edges smooth from transportation

Round

Well-rounded from years of being transported

TABLE 1-4 Descriptive Terminology for Grain Size Term

Size limit

Example

Boulder

12 in. (305 mm) or larger

Basketball size or larger

Cobble

3 - 12 in. (76 – 305 mm)

Grapefruit size

Coarse Gravel

¾ - 3 in. (19 – 76 mm)

Lemon size

Fine Gravel

#4 sieve - ¾ in. (4.75 – 19 mm)

Grape or pea size

Coarse Sand

#10 - #4 sieve (2 – 4.75 mm)

Uncrushed peppercorn

Medium Sand

#40 - #10 sieve (425 μm – 2 mm)

Sugar or table salt crystal

Fine Sand

#200 - #40 sieve (75 μm – 425 μm)

Powdered sugar

Silt/Clay

25mm/1")

4.5

* A pocket penetrometer should be used when available. Especially when testing Trench Walls per OSHA 29, Subpart P. Compressive strength readings are in TSF (Tons per Square Foot)

TABLE 1-7 Descriptive Terminology for Relative Consistency of Fines Using the SPT, 140-lb Hammer/30-in. Drop N value (blows/ft)

Term

Symbol

30

Hard

H

Note: moisture content and variations in material types can cause variable blow counts.

11

Chapter 1: Field Soil Classification

TABLE 1-8 Descriptive Terminology for Relative Density for Coarse-Grained Soil Using the SPT, 140-lb Hammer/30-in. Drop N value(blows/ft)

Term

Symbol

0–4

Very Loose

VL

5–10

Loose

L

11–30

Medium Dense

MD

31–50

Dense

D

>50

Very Dense

VD

Note: moisture content and grain size can cause variable blow counts.

TABLE 1-9 Descriptive Terminology for Carbonate Cementation Term

Reaction to dilute HCl

None

No reaction

Weak

Weak to moderate fizzing

Strong

Violent fizzing

Materials formed or cemented by carbonates (such as limestone and caliche) will react with HCl, whereas most materials cemented by—or composed primarily of— silica will not. Placing a drop of dilute Hc1 on the mineral or soil in question is an easy way to distinguish whether it is carbonate-based. This is also a quick method to help differentiate calcite (which will fizz in dilute HCl) from gypsum (which will not react to dilute Hc1)—and will help to distinguish crushed limestone from diatomaceous soil, which will have no reaction to dilute Hc1. A 20% hydrochloric acid and 80% water solution may be used for this test.

TABLE 1-10 Descriptive Terminology for Odor Term

Example

None

No odor noticeable

Earthy

Moldy or musty odor

Chemical

Includes oily odor

Organic

Odor from manure or decay

12

Chapter 1: Field Soil Classification

TABLE 1-11 Descriptive Terminology for Dry Strength Term

Field test

None

The dry sample crumbles by the mere pressure of handling— indicating no plasticity and low to no cohesion

Low

The dry sample crumbles under light finger pressure— indicating low plasticity and low cohesion

Med

Considerable finger pressure is necessary to break the dry sample— indicating low to medium plasticity and high cohesion

High

The dry sample can only be broken between your thumb and a hard surface—indicating that the sample has medium to high plasticity

V High

The dry sample cannot be broken between your thumb and a hard surface—indicating that the sample is highly plastic

TABLE 1-12 Descriptive Terminology for Plasticity (when moist) Term

Plasticity Index (PI)

Field test

Non-plastic

0–3

Cannot be rolled to ⅛ in.

Slightly plastic

4–15

Rolled to ⅛ in. with care

Medium plastic

16–30

Easily rolled to ⅛ in.

Highly plastic

31 or above

Will roll into a thin thread

Note: Some geotechnical engineers use the PI as a quick estimate of expansion—with a PI >15 often used to indicate a soil with expansive potential. However, the Expansion Index (EI) test is the best indicator.

Chapter 1 Questions 1. Porosity of a soil may indicate that the soil is: (a) Well graded (b) Engineered fill (c) A natural formation 2. Sand particles will not pass what sieve size? (a) No.200 (0.075 mm) (b) No.4 (4.75 mm) (c) No.100 (1.50 mm)

Chapter 1: Field Soil Classification

3.

A soil composed of 65% sand, 30% silt, and 5% clay could best be described as a: (a) SC (b) SM (c) ML (d) None of the above

4.

A soil composed of 50% sand, 25% clay, and 25% silt could best be described as a: (a) CL/ML (b) SC/SM (c) SM/CL

5.

Which of the following are good indicators that a soil is more clayey than silty? (a) Light in color and porous (b) Low dry strength and feels soft when wet (c) High dry strength and no dilatancy reaction (d) None of the above

6.

Which two examples best describe an artificial fill type of soil? (a) Naturally deposited material, such as alluvial or slide debris (b) Soil with construction debris (glass, brick, etc.) (c) Documented engineered fill (d) Porous topsoil

7.

A soil classified by the USCS symbol of CH would have which two characteristics? (a) Finer than ssthe No.200 sieve (b) High porosity (c) High dilatancy (d) High plasticity

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2 Exploration and Sampling Methods Before a grading project can begin, a geotechnical investigation report, agency reviews, and other approvals are required. The geotechnical report describes the existing surface and subsurface conditions of the grading site and provides recommendations, including removal depths of unsuitable soil, compaction and moisture conditioning requirements. Exploration methods used to obtain material for lab testing and subsurface profiling information may include borehole drilling and sampling, backhoe trenching, cone penetration test (CPT), seismic refraction, or other more involved geophysical methods. Upon review of the existing surface conditions—and considering the proposed cuts, fills, and structures to be built—the project manager decides what type of sampling method(s) may best suit the site. In hilly terrain, a geologist is directly involved in the exploration activities. Whereas, in areas where geologic conditions are generally well known (such as flatlands with thick soil cover) the soil engineer designs the sampling program, with coordination from the geologist. The soil technician, engineer in training (EIT), or geologist in training (GIT), often logs boreholes or trenches for site investigations. A training process should be completed with an experienced logger prior to the technician (EIT or GIT) working independently. When on site to perform the investigation, if no current site plan is available, existing surface features such as: stockpiled fill, old building materials, protected trees, wetlands—along with planned sampling locations—may be overlain on a satellite view photo and used as a site plan. While backhoe trenches are often suitable for shallow site investigations, most explorations require a drill rig (such as the one shown in Figure 2-1) to obtain soil samples. However, logs must be filled out for both borings and trenches, similar to Figures 2-3 and 2-7. Before any subsurface investigation takes place (boring, digging or otherwise) all existing underground utilities must be located within

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Chapter 2: Exploration and Sampling Methods

Figure 2-1

Drill Rig This drill rig can perform hydraulic down hole sampling or shallow well drilling. On this levee project, this rig was used to drill relief wells around the interior ring of a newly constructed levee. The levee was built around the existing South River Pump Station (SRPS) to help protect it during high water events. The SRPS is located along the west side of the Sacramento River, just north of Clarksburg, California. Because much of the new levee is underlain by variably dense pervious silty sands, relief wells were drilled to depths of approximately 75 ft and designed to drain ground water seepage (to reduce hydraulic pressure to the levee embankment) into the newly designed concrete V-ditch; and then subsequently pumped back into the Sacramento River.

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Chapter 2: Exploration and Sampling Methods

the work zone! Utilities must be contacted via a common utility hotline (typically 811) at least 48 hours prior to any underground work. A locating service should then be dispatched.

BOREHOLES Boreholes are used for sampling and logging soil as drilling progresses from near-surface elevation to hundreds of feet or more. Determining the sampling method or equipment to use is dependant on the material to be sampled, the geotechnical information desired, and even the terrain accesability. For instance, a 4wd drill rig may be necessary to traverse sand dunes, or muddy surfaces. Figure 2-1 shows a drill rig equipped with auger that can perform downhole soil sampling, or relatively shallow well drilling.

The Standard Penetration Test (SPT) One type of borehole sampler is the SPT, which is a hollow split barrel type (sometimes referred to as the 'split spoon', because the barrel is made to be split open lengthwise to allow for easier sample removal). SPT split barrel samples are considered disturbed and are used for visual identification in the field and limited lab testing for classification purposes only. When using an SPT sampler (Figure 2-2), the relative density or consistency of a soil may be determined concurrent with sampling. This method involves counting the number of blows (a 30 in. drop of a 140 lb hammer) taken to drive the split barrel sampler one and one-half feet (18 in.). While driving the SPT into the soil formation, a blow count (referred to as the “N value”) can be obtained. From the last 12 in. cumulative blow count the approximate relative density or consistency of the soil is calculated (Table 2-1).

Procedure Using either a solid or hollow-stem auger, the hole is bored to the initial sampling depth. If a solid auger is used, the auger must be withdrawn from the hole before the sampler can be lowered back down into the hole. However,

Figure 2-2

Split Barrel (SPT) Sampler The split barrel sampler, consists of four main parts: the drive shoe, the split barrel, the waste barrel, and the adapter head.

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Chapter 2: Exploration and Sampling Methods

Table 2-1 N value for the Standard Penetration Test (SPT) Relative Density for Coarse-Grained Soil

Relative Consistency for Fine-Grained Soil

Relative Density

Penetration Resistance in blows/ft (N)

Relative Consistency

0–4

Very Loose

50

Very Dense

16–30

Very Stiff

>30

Hard

Penetration Resistance in blows/ft (N)

Note: Coarse-grained soils are predominantly sands, and fine-grained soils are predominantly silts and clays.

when a hollow-stem auger is used, the sampler is attached to a drill rod and lowered down the hole, inside the hollow-stem auger. The hollow-stem auger then acts as casing to help minimize any caving or sloughing—while also eliminating the step of auger removal. With the split barrel sampler attached to the tip of the drill rod, a 140 lb hammer is seated over the top of the drill rod; then raised 30 in. and dropped, driving the sampler into the soil formation below. The number of 30 in. drops (blow counts) are counted for each half-foot (6 in.) increment driven, until the sampler has been driven 1.5 ft (18 in.). The blow counts for the first 6 in. are recorded, but these are not used to calculate the N value, since a portion of the first 6 in. is often disturbed during the drilling process. All blow counts should be recorded on the boring log, as shown in Figure 2-3. The total drops taken to drive the sampler the last 12in. is considered the N value (Table 2-1). If the blow count for any half-foot increment reaches 50, the distance the sampler was driven should be measured and recorded—the split barrel sampler should then be removed from the hole. Further effort to drive the sampler into consistently hard materials may damage the drive shoe or get the sampler stuck. Note: If the material being sampled is predominantly non-cohesive (such as clean sand), the soil may tend to slip out of the sampler as the barrel is raised from the hole. Under these conditions it may be necessary to install a “sample grabber” between the drive shoe and the sample barrel to help keep any material from slipping out during

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Chapter 2: Exploration and Sampling Methods

Figure 2-3

Boring Log

Chapter 2: Exploration and Sampling Methods

sample recovery. The sample grabber allows the sandy soil to pass up into the sample barrel but closes up as the barrel is being removed. After the sampler is disconnected from the drill rod, and placed horizontally on the work table or tailgate, the drive shoe and waste barrel are unscrewed from the sample barrel. The sample barrel is then opened along the split (lengthwise). The length of the sample should be measured and then recorded on the log—as the amount of recovery. Finally, the sample should be visually classified, sealed (airtight) in a plastic bag or jar, and then labeled prior to transporting it to the lab. Tip: Experience has shown that it is wise to use an indelible black marker to label directly onto the sample bag; this will help to eliminate losing information when samples arrive back at the lab; often times with wired tags or stick-on tags missing from breaking or blowing off!

Sampling with Rings The method for taking ring samples is similar to split barrel sampling, since both are types of drive sampling, and most ring samplers are also split barrel type. The sample barrel diameter for the SPT is 2 in. diameter, while the California Modified Ring Sampler has a larger diameter of 3 in., as depicted in Figure 2-4. This is to allow twelve 1 in. tall by 2½ in. diameter rings to fit inside the sample barrel. Since ring samples are considered relatively undisturbed, they can be used to run many lab tests, including: consolidation, direct shear, moisture, and density. California Modified Samplers may also be fitted with three 6 in. long by 2½ in. brass tubes.

Procedure When the ring sampler is driven into the subsurface by 30 in. drops of the 140-lb hammer, the soil sample is forced into the rings within the sample barrel. If an N value is to be calculated from the blow counts when ring sampling, a conversion factor must be used for the larger 3 in. diameter barrel of the California Modified Ring Sampler, as shown by Table 2-2.

Figure 2-4

California Modified Ring Sampler

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Chapter 2: Exploration and Sampling Methods

Table 2-2 N value for the Modified California Ring Sampler (3 in. O.D. by 2½ in. I.D.) Relative Density for Coarse-Grained Soil Penetration Resistance(N) (blows/ft)

Relative Density

Relative Consistency for Fine-Grained Soil Penetration Resistance (N) (blows/ft)

Relative Consistency

0–2

Very Loose

28

Very Dense

9–17

Very Stiff

>17

Hard

N values derived from article in Environmental and Engineering Geoscience, May 2006; Rogers, J. David, PhD. (Side-by-Side Correlations—Sampling performed 1991-1996 in Northern & Southern California), suggesting a Modifed CA correlation value of 0.55 of SPT N. Other investigators have recorded varied correlation values under differing conditions and sampler variations.

After the sampler is brought to the surface, the drive shoe and waste barrel are disconnected from the sampling barrel. The rings are then extruded from the sample barrel by use of an extraction device, or the ring sampler may be opened lengthwise if it is of a split barrel type—allowing for easier ring removal. As the rings from the sampler are carefully removed, they can be slid into a plastic sample container, and sealed air-tight. Should the sample be short, crumpled plastic may be pushed between the soil and lid to keep the soil from moving. The container should be labled on top with appropriate information, such as borehole, soil type, sample number, depth, project number, date, and initials. The container should be sealed with tape (for moisture retention) and then placed in foam-padded boxes prior to transportation (Figure 2-5). During removal of the rings from the barrel, do not bang on the barrel; this will disturb the sample, thus destroying the chance for accurate density, consolidation, direct shear, or other testing. For opening split barrels, the use of a large knife or flat-head screwdriver works well. To help separate the rings (especially with clayey soils or slightly cemented soils) a piano wire stretched across a hacksaw may be helpful.

Chapter 2: Exploration and Sampling Methods

Figure 2-5

California Modified Ring Sampler: Barrel, Rings, and Padded Storage Box. (A) The drive shoe and the waste barrel are shown unscrewed from the sampling barrel, which splits lengthwise for easy ring insertion or removal. (B) Different drive shoes (or heads) may be used depending on varying soil conditions. Upon recovery, the full rings can be stored in a lidded plastic can. The full sample cans may then be stored in foam-padded boxes. (C) The ring sampler shown here looks similar to the SPT sampler, although the SPT sampler has a smaller diameter body. Both samplers are driven into the formation by 30 in. drops of a 140 lb hammer, for a total drive depth of 18 in. The N Value is calculated from the final 12 in. (Table 2-2).

Thin-Walled Tube Sampling Tube sampling disturbs the sample less than drive sampling methods. Tube samples may be used for all types of testing, from basic classification tests to more complex testing, such as triaxial tests. Tube sampling is known as “thinwalled sampling” or by brand names such as Pitcher and Shelby. Tube sampling is commonly performed from a rotary drill rig by using air or drill mud to keep the boring clear of cuttings and to stabilize the borehole walls. A Pitcher type sample tube is typically 3 ft. in length, with a 3 in. outside diameter (OD) and an approximately 2 7/8 in. inner diameter (ID). The tube is slid up inside a sample barrel. The Pitcher sample barrel is equipped with a sawtooth bit at the leading end (Figure 2-6) and is spring-loaded to help keep even down pressure at the tip of the tube while sampling.

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Chapter 2: Exploration and Sampling Methods

Figure 2-6

Pitcher Tube Sampler

Procedure The sample barrel is connected to a drill rod and lowered to the bottom of the bore hole. While the teeth of the sample barrel slowly cut a hole around the tube, the tube is pushed into the soil formation by a steady downward pressure. The sample tube should always lead the sample barrel, helping to ensure an undisturbed sample. Since the sample tube is made of relatively thin steel, it can easily be damaged by rocks and hard or cemented layers of soil, or by the application of too much down pressure. For this reason, it is important to have an experienced drilling crew to properly maintain or release pressure to collect a good sample.

Chapter 2: Exploration and Sampling Methods

Note: An experienced driller will back off if a lot of “rod chatter” or bouncing of the drill rods occurs, or when too much down pressure is necessary to push the sampler ahead. When tube sampling, it is more important to recover a shorter less-disturbed sample, in lieu of a longer disturbed sample that may be unusable for undisturbed testing purposes. After the sample is retrieved, the tube is disconnected and removed from inside the sample barrel. The soil at the tube bottom (tip) should be cut flush and then sealed with a plastic cap. The amount of recovery should then be measured by inserting a ruler into the top end of the tube until resistance is felt by undisturbed material. The amount of recovery is entered on the boring log (Figure 2-3). It is a good idea to draw arrows on the outside of the sample tube (with indelible pen), pointing in the upward (surface) direction. Crumpled plastic may be pushed between the soil and top lid to keep the soil from moving. Both caps should be sealed air-tight with tape (and waxed if desired). When moving these samples to the lab, they must be placed in well-padded containers and transported carefully in the upward position. This will help to minimize any disturbance during transport. Once at the lab, the tubes can be cut to the desired length with a tube cutter. Care should be taken while cutting the metal tube not to apply too much pressure, which could cause the barrel to become ‘egg shaped’ and disturb the sample. The sample may then be carefully pushed out of the tube with an extruding device. Care should be taken to record all logging information onto the log sheet. A complete log should include the data (listed as follows) and on Figure 2-3. v A visual soil description at each observable material change, including using the USCS v Estimation of relative density or consistency of soil v Ease of drilling; including down pressure, rod chatter and refusal at depths encountered v Initial depth water is encountered, its static level, and if possible, flow rate v Caving or sloughing v Depth or thickness of fill; noting fill indicators and any encountered debris v Soil porosity, rootlets, organics, odor v Grain shape, size, HCl reaction, bedding, stratification, and other characteristics v Color and variegation, often based on Munsell color chart Note: It is wise to document as much information as possible during the exploratory process; inconsequential information can always be omitted from the boring or trench logs at a later time.

Backhoe Trenches Excavating a number of trenches or pits with a backhoe (or a larger excavator) is one method of securing soil samples, as well as an excellent way to observe insitu subsurface site conditions. Trench excavations may be especially helpful to

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Chapter 2: Exploration and Sampling Methods

the geologist in viewing bedding, slide planes, seeps, faulting, the condition of inplace bedrock, and other features of geologic concern. Better views of old fill and/or debris can be seen along the larger exposed trench walls, as opposed to a smaller downhole sample. The relative ease with which a trench can be dug is also significant information. If the soils are tightly cemented or bedrock is encountered, the hardness of excavation or depth to refusal is valuable information for the grading contractor when determining excavatability. Such information may aid in electing whether to use a large dozer to rip through hard material, or if blasting is necessary to sufficiently loosen or break up a cemented soil or hard rock formation, allowing for easier site grading. As the exploration trench is dug, level steps may be excavated at desired elevations to allow for in-place density tests, pocket penetrometer, shear vane tests, and more. Remember to always follow trench safety guidelines (per OSHA). Bag samples can be collected as needed, usually at each significant soil change. The job name, project number, date, trench number, sample depth/elevation, and visual soil classification should be included on the label of each bag. An accurate trench log must be kept, Figure 2-7 presents a graphic representation of a trench log. Quite often, the graphic profile of subsurface conditions is the most valuable information retained on a project, allowing for a quick view of subsurface conditions at a future date. Along with soil descriptions, it is important to indicate on the log whether any caving or sloughing occurred during excavation, and at what depths. Note the depth of any water encountered, and its source when possible (groundwater, seep, etc.). Also, attempt to determine the approximate flow rate of the water. Draw your own plot plan if one does not exist. Be sure to ‘tie in’ the site location with a relatively permanent marker, such as a curb, telephone pole, building, wash, or even protected trees. Remember to note trench direction and length. Include a north arrow for trench orientation, and add the scale of your drawing.

Rock Hardness Study Often an investigation is performed to help determine the hardness (excavatability) of volcanic flow, bedrock, or cemented formations. This information is then used by the grading contractor to determine the best methods for removing the hard material, and the extent to which it exits. Methods of removal may include hydrohammers, rock saws, heavy dozers using a single shank (ripper), or blasting. One of the simplest rippability investigation methods is to use a large dozer with a single shank and attempt to rip the rock to determine the feasibility of ripping or other mechanical removal to the required grade. Refer to Table 2-3 for a general guide to Rippability vs Blasting. Another common method is to utilize a large excavator and attempt to dig through the rock surface to help ascertain the feasibility to excavate for utility trenches.

Chapter 2: Exploration and Sampling Methods

Figure 2-7

Trench Log

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Chapter 2: Exploration and Sampling Methods

Table 2-3 Excavatability Classification Table Velocity (ft/s)

Rippability

0 to 2000

Easy Ripping

2000 to 4000

Moderate Ripping

4000 to 5500

Difficult Ripping (possible blasting)

5500 to 7000

Very Difficult Ripping (blasting likely)

>7000

Blasting usually necessary

This table should be used as a general guide only, as many local factors such as cementation and the spacing or orientation of rock fractures may affect excavatability. For this chart ‘ripping’ is based on the ability of a D-9 dozer with a single shank to break up the rock for removal.

Another easy study to help determine rippability is the Geophysical Seismic Refraction Survey. This procedure includes placing a number of seismic traverses (seismic lines)— laid out, with the length of each line (cable) placed dependent on the depth necessary to perform the required evaluation. Typically, the effective depth of evaluation is approximately one-third to one-fifth the length of the seismic line. Geophones are placed at specific intervals and are connected by electrical wire to establish the line. Commonly, a metal plate is placed on the ground at one end of the seismic line; the plate is struck by a sledgehammer to generate seismic waves at the surface. These waves are refracted beneath the surface by soil or rock materials of varying densities (hardness), thus creating contrasting velocities. The refracted seismic waves are then detected by the geophones, which send the velocity times to the seismograph for recording. Since seismic waves generally travel faster through harder formations, a higher velocity usually indicates harder rock. Compare velocities versus ripping by a dozer using the quick reference Table 2-3.

Chapter 2 Questions 1. One main advantage of a ring sampler over an SPT sampler is: (a) Gradation tests can be performed only on a ring sample. (b) Ring samples are considered relatively undisturbed, allowing for more varied lab testing. (c) Moisture tests are more accurate when performed on ring samples. 2. Which exploration technique is the best to observe shallow geologic strata? (a) Backhoe trenching (b) Split barrel sampling (c) Tube sampling

Chapter 2: Exploration and Sampling Methods

3.

Choose the two best methods for determining excavatability of rock: (a) Ripping with single shank dozer (b) Split barrel sampling (c) Tube sampling (d) Seismic Refraction Survey

4.

A blow count of 23 for an SPT sampler driven into a sandy soil would indicate: (a) A relative density of “medium” (b) Refusal (c) A relative consistency of “stiff”

5.

A seismic velocity of 2100 ft/s would indicate to the contractor that blasting is necessary. (a) True (b) False

6.

During removal of rings from the ring sampler barrel it is best to hit the barrel with a hammer to loosen the rings. (a) True (b) False

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3 Basic Laboratory Tests Laboratory testing determines soil attributes by approved test methods, such as standardized tests. These methods are a consistent way to characterize in-situ and imported soil properties, including: particle size, plasticity, expansion, moisture content, strength, and to obtain a myriad of other important data. Although there are many different and more involved lab tests, some of the more commonly used are presented in this chapter. Each test described herein include general outlines, while sometimes giving more detailed test suggestions and procedures. The outlined test procedures in this book are not meant to supplant referenced ASTM or any other standard test methods. Always refer to the current standards required for the project being evaluated. Engineers evaluate the cumulative resulting information of laboratory tests to help define how a soil will act under specific construction or natural conditions. Some common tests used during geotechnical investigations include: Particle size (sieve and/or hydrometer analysis): is always used for soil classification purposes, and often for specific studies—such as liquefaction, drainage, or slope stability. Permeability: is commonly used to help determine core and embankment soil for use during levee construction or design criteria (infiltration) for bioretention basins, infiltration trenches, and other LID features. Resistance (R) value and Expansion Pressure: are utilized in measuring the strength of subgrade, subbase, or aggregate base to help calculate the thickness of asphalt or other cover material necessary for roads, or even airport runways. Plasticity Index: helps in classification of clay and silt—including amount of plasticity, estimation of permeability or shear strength, and as an indicator of expansion potential (shrink-swell) beneath foundations; with the Expansion Index (EI) test being the better indicator of the latter. Laboratory test procedures are governed by many different agencies, each requires specific standards, these agencies may include: international (such as ASTM and ASCE), national (such as AASHTO and FHWA), state, regional, or local municipalities.

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Chapter 3: Basic Laboratory Tests

Within this book, reference to a similar test method may be noted. However, the most current approved or applicable test method to meet project specific requirements should always be employed.

Modified Proctor/Maximum Density Test The modified Proctor test (ASTM D1557) determines the moisture content at which a given soil type will compact best (i.e., achieve maximum density). This moisture–density relationship resulting from the modified Proctor test is often called the maximum density test or compaction curve. The compaction curve is determined by compacting a given volume of soil at a known moisture content into a specific-sized cylindrical mold. The original “Proctor test” was established by Ralph. R. Proctor in 1933. ASTM test method D698 (referred to as the “standard Proctor”) is very similar to the method proposed by Ralph Proctor. Both ASTM test methods (D1557 and D698) use a ‘free-fall drop’ of the hammer. The modified Proctor test was introduced as an ASTM standard in 1958. As compaction equipment became larger and heavier over the years (larger vibratory compactors, bigger sheepsfoot rollers, and other equipment) and due to far heavier loads being transported across roads and highways—it became necessary to have a higher, more relevant compaction standard. Thus, the modified Proctor became more widely used as a modern replacement for the standard Proctor. The primary differences between the modified Proctor and the standard Proctor are the hammer weights, the height of the drop, and the number of soil layers placed into the mold. The older standard Proctor utilizes a 5.5 lb hammer with a 12 in. drop, and three layers, whereas the modified Proctor uses a 10 lb hammer with an 18 in. drop, and five layers. There is a considerable difference in the resulting maximum density between the standard Proctor and the modified Proctor. The standard Proctor creates an effort of approximately 12,400 ft-lbf/ft3, while the modified Proctor produces a force of about 56,000 ft-lbf/ ft3. Misconceptions have been made during the transition from the use of the standard Proctor to the modified Proctor regarding correlations between each Proctor type. A common misunderstanding is that a 100% compaction obtained by the ASTM D698 standard Proctor is equivalent to a 95% compaction achieved by the ASTM D1557 modified method. Since the difference in load applied during each test is so great, and the resulting comparisons will often vary depending on soil type; a correlation chart between the two compaction methods is not practical. The modified Proctor is prepared in the lab in the same way as the standard Proctor test (methods A, B, and C; per ASTM) for various soil types. However, geotechnical engineers routinely adjust the moisture and density required in the

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Chapter 3: Basic Laboratory Tests

field (percent moisture and degree of compaction) when utilizing the modified Proctor—dependent on the soil type or fill loading requirements. For instance, an aggregate base may typically be compacted to 95% (±2% of optimum moisture) for most roadways. Conversely, where heavier live loads are expected (such as airport runways) it is not unusual for the geotechnical engineer to recommend 100% compaction. And, when compacting more clayey soils—or using material for levee or dam core material—the geotechnical engineer may recommend a lower density and higher moisture content (i.e., 87% to 92% placed at 2% to 4% over optimum). Yet, for general fill, 90% of the modified Proctor at ±2% of optimum moisture is often used. Note: Projects vary; familiarize yourself with the compaction and moisture standards.

Synopsis of test methods The test method described in this section is for a sample with no more than 20% of material retained on the No. 4 sieve, similar to ASTM D1557 test method A. The laboratory compaction of the sample is performed by dropping a 10 lb hammer 25 times per layer, compacting a total of five equal layers into a 4in. diameter mold. The amount of soil compressed into the mold is then weighed. For methods A and B—25 drops are used, with a 4 in. diameter mold, whereas test method C (containing up to 30% of 3/4 in. size material) is compacted in a 6in. diameter mold—using 56 blows per layer. This compaction procedure is repeated at various moisture contents (usually four)—from dry to wet. Each moisture content can be plotted against the corresponding dry density of the soil on graph paper (Figure 3-3), creating a “compaction curve.” The point at the top of the curve is where the “optimum moisture” and “maximum density” converge. This point is referred to as the laboratory “maximum dry density”. The moisture content at the maximum dry density is the water content at which the soil will generally compact best during the field grading process. When a field density test is taken (either by nuclear gauge or sand cone), the field dry density value is divided into the laboratory maximum density, the result of which is the percent (degree) of compaction at the location tested. That degree of compaction must fall within the specified compaction for the project.

Apparatus The equipment needed to perform the modified Proctor method A test consists of the following: v Mold: 4 in. diameter by 4.58 in. height, for a volume of 1/30 of a cubic foot. (Figure 3-2) v Hammer: 10 lb with an 18 in. drop and with a 2 in. circular face; may be manually or mechanically operated.

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Chapter 3: Basic Laboratory Tests

v Scales: A larger scale with a 20 kg minimum capacity (approximately 1 g accuracy) and a smaller 1 kg scale (approximately 0.1 g accuracy) v Sample extruder: A hydraulic car jack or other adapted equipment to help remove the soil from the sample mold v Steel straight edge: Approximately 1in. long by 2 in. wide and having one beveled edge. v Sieve: No. 4 (4.75 mm) v Oven: Thermostatically controlled to maintain a temperature of 230 °F (110 °C) v Additional equipment includes a graduated cylinder (in milliliters), mixing tools, mixing pans, and moisture sample containers. The moisture containers should be numbered, pre-weighed, and labeled.

Procedure Obtain a large (50 lb minimum) bulk sample from the field. While obtaining the material, the sample must be visually classified (using the USCS), and the sample description (including where the sample was obtained) should be written on the field sample tag (Figure 3-1). To begin the test, pass the material through the No. 4 sieve, setting aside any plus No. 4 material. For this test it will be assumed that less than 5% of the material is retained on the No. 4 screen, so no ‘oversize correction’ will need to be calculated. After the sample is passed through the sieve, the initial moisture content should be brought to a few percent under optimum by either adding moisture or by drying the soil. For an SM type soil, a good starting moisture will be when you can squeeze the soil in your palm, and it will just barely cling together. Tip: Excess moisture can be reduced by spreading the sample on a concrete floor, using a fan, or drying the material in a low-temperature oven ( No. 10 material and 0.01 g for weighing < No. 10 material v Sieve shaker: preferably with a timer v Oven: set at 230 °F (110 °C) v No. 200 wash sieve: a sieve with high sides (75 μm) v Sink: with a small hose to rinse soil through the wash sieve v Soaking solution: sodium hexametaphosphate solution (40 g per liter of distilled water) v Soaking container: metal pan, porcelain bowl, or a similar container that has been numbered, pre-weighed, and labeled with indelible ink

Procedure Place a representative portion of the soil sample in the oven until it is thoroughly dried. For material ⅜in. and smaller, a minimum sample of 500 g will suffice. Weigh the initial sample. Enter this weight as the total sample weight. Pour the sample into the soaking pan. Fill the pan with enough soaking solution to completely cover the sample. Low cohesive soils should be allowed to soak a minimum of 2 hours. Moderate to highly plastic soils should soak overnight to soften and break down the adhesion of clay and silt particles.

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Chapter 3: Basic Laboratory Tests

After the soaking is complete, wash the sample over a No. 200 wash sieve. Continue to wash the sample until no more fines (silt or clay) appear to be passing through the sieve. Then, carefully position the sieve over the soaking pan and rinse the remaining soil back in. Pour off the excess water, taking care not to pour out any of the remaining soil. Place the sample into the oven to dry. Arrange a set of sieves in order of opening size—from large to small, top to bottom (Figure 3-4). Remove the dry soil from the oven and pour the soil into the top sieve, using a brush as necessary to dislodge all adhering soil from the sample pan. Cover the stacked sieves and tighten them onto the shaker. Let the sieves shake for at least 15 minutes, or until all the grains of soil have passed through all the sieves possible. After shaking, weigh the soil from each sieve, starting with the largest screen, then adding each weight together (weighing in a cumulative manner). Record each weight on the test sheet, as shown in Figure. 3-5. Tip: To help remove material from the larger screens, use a small stiff wire brush. A softer brush should be used on the smaller size (nylon) sieves.

Figure 3-5

Sieve Analysis Test Sheet

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Chapter 3: Basic Laboratory Tests

Calculations (refer to Figure 3-5) 1. 2. 3.

Cumulative weight of soil retained = weight of soil retained on each individual sieve + cumulative weight retained on all larger sieves Weight of soil passing = total weight of soil - cumulative weight Percent finer = [weight of soil passing / total weight of soil] × 100

Hydrometer Analysis The hydrometer analysis uses a sedimentation process to determine the particle size distribution of material finer than the No. 200 sieve. A grain-size distribution curve may be drawn from the resulting figures and may be combined with the grain-size curve obtained from the plus No. 200 material.

Apparatus v 1,000-ml sedimentation cylinders: approximately 18 in. tall by 2.5 in. diameter v Hydrometer: 52H v Sieves: No. 10 (2 mm) and No. 200 wash sieve (75 μm) v Bowl with pestle: hard rubber-tipped pestle preferred. v Scales: accurate to 0.1 g (for material retained on the No. 10 sieve) and 0.01 g (for material passing the No. 10 sieve) v Squirt bottle: used to rinse material from the inside of cups and cylinders v Thermometer: accurate to 1 °C v Dispersing solution, to deflocculate fine particles: sodium hexametaphosphate solution (40 g per liter of distilled water) v Dispersing containers: small porcelain bowls or similar containers v Weighing containers: tared and numbered with indelible ink v Mixing apparatus: for example, a milkshake mixer with a mixing cup v Timing device: watch, clock, and timer Note: All water used should be distilled and the room in which the analysis is done should have a fairly constant temperature.

Procedure Air dry a representative sample. Break it up with a pestle in a bowl. Next, pass the specimen through the No. 10 sieve, allowing for enough material to be weighed out as follows: if the selected material is predominantly clayey or silty, use ≥50 g of soil; if the sample is primarily sandy, use ≥100 g of material. Place the portion in a dispersing bowl, add 125 ml of dispersing solution, and stir well. Let the mixture soak for at least 16 hours. After the soaking period, using a squirt bottle of distilled water and transfer the mixture into the mixing cup. Fill the mixing cup about half full with more distilled water. Mix for one minute. Next transfer the composite into a 1,000 ml sedimentation cylinder; again, a

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Chapter 3: Basic Laboratory Tests

squirt bottle may be used to aid the transfer. Fill the cylinder to the 1,000 ml level with distilled water. Using a rubber stopper (or the palm of your hand) to cover the top of the cylinder, turn the cylinder upside down and back for a period of one minute, inverting the cylinder approximately one turn per second. When finished, place the cylinder on a level surface and remove the stopper from the top. Immediately observe the time and record it on the test sheet (see Figure 3-7). Upon completion of shaking, the hydrometer readings should be noted and recorded as the actual reading at the following intervals: 2, 5, 15, 30, 60, 250, and 1,440 minutes. At each time interval, a control reading should be recorded from the control sedimentation cylinder. Temperature readings are also recorded from the control sedimentation cylinder at each interval. Hydrometer readings must be read at the top of the meniscus (the top of the water surface formed around the hydrometer stem). Between readings, the hydrometer should be placed in the control cylinder, not left in a test cylinder. See Figure 3-6 for a typical test arrangement.

Figure 3-6

Hydrometer Test Arrangement

Figure 3-7

Hydrometer Analysis Test Sheet

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Chapter 3: Basic Laboratory Tests

TABLE 3-1 Values for L Actual hydrometer reading

Effective depth, L (cm)

Effective depth, L (cm)

Actual hydrometer reading

0

16.3

26

12.0

1

16.1

27

11.9

2

16.0

28

11.7

3

15.8

29

11.5

4

15.6

30

11.4

5

15.5

31

11.2

6

15.3

32

11.1

7

15.2

33

10.9

8

15.0

34

10.7

9

14.8

35

10.6

10

14.7

36

10.4

11

14.5

37

10.2

12

14.3

38

10.1

13

14.2

39

9.9

14

14.0

40

9.7

15

13.8

41

9.6

16

13.7

42

9.4

17

13.5

43

9.2

18

13.3

44

9.1

19

13.2

45

8.9

20

13.0

46

8.8

21

12.9

47

8.6

22

12.7

48

8.4

23

12.5

49

8.3

24

12.4

50

8.1

25

12.2

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Chapter 3: Basic Laboratory Tests

TABLE 3-2 Values for K Temperature (°C)

Values for K by Specific Gravity 2.55

2.60

2.65

2.70

2.75

2.80

16

0.01481

0.01457

0.01435

0.01414

0.01394

0.01374

17

0.01462

0.01439

0.01417

0.01396

0.01376

0.01356

18

0.01443

0.01421

0.01399

0.01378

0.01359

0.01339

19

0.01425

0.01403

0.01382

0.01361

0.01342

0.01323

20

0.01408

0.01386

0.01365

0.01344

0.01325

0.01307

21

0.01391

0.01369

0.01348

0.01328

0.01309

0.01291

22

0.01374

0.01353

0.01332

0.01312

0.01294

0.01276

23

0.01358

0.01337

0.01317

0.01297

0.01279

0.01261

24

0.01342

0.01321

0.01301

0.01282

0.01264

0.01246

25

0.01327

0.01306

0.01286

0.01267

0.01249

0.01232

26

0.01312

0.01291

0.01272

0.01253

0.01235

0.01218

27

0.01297

0.01277

0.01258

0.01239

0.01221

0.01204

28

0.01283

0.01264

0.01244

0.01225

0.01208

0.01191

29

0.01269

0.01249

0.01230

0.01212

0.01195

0.01178

30

0.01256

0.01236

0.01217

0.01199

0.01182

0.01165

After the final reading has been taken, transfer the mixture out of the cylinder onto a No. 200 sieve and continue to wash it until no more particles are observed to pass through the sieve. Transfer the retained grains on the sieve (using a squirt bottle as needed) into a previously tared container. Dry the material in the oven. Enter the weight of the dry material on the test sheet as Dry Weight of Soil Retained on the No. 200 sieve.

Calculations The following calculations are performed at each time interval: (R) corrected reading = actual reading – control reading (P) percent finer = [R (a/s)] × 100 Where: s = original weight p of ffiffiffiffiffiffiffiffiffi soilffi sample, a = 1.00 (for most purposes) (D) particle diameter = K L=T (T) = time elapsed (L) effective depth = values from Table 3-1 (K) value for specific gravity versus temperature = values from Table 3-2

Chapter 3: Basic Laboratory Tests

Plastic and Liquid Limits Test This test (sometimes referred to as the Atterberg Limits) is used to determine the Plasticity Index (PI) of silty and clayey soils. Commonly a PI of 15 or greater is employed as a guide to indicate potentially expansive soil. Different types of clay have varying expansion potential. Montmorillonite, bentonite, and vermiculite are known to have high expansive capabilities, while kaolinite and micaceous clays generally have lower expansion. Although the PI of a clay may be a good general indicator of shrink swell (expansion) potential, a test for a more accurate determination of expansion capability is the Expansion Index test (EI). There are also observable indicators of expansive soil, including when an expansive soil dries out— shrinkage or desiccation cracks can be seen. Definitions Plastic Limit: (1) The water content at which a soil will just begin to crumble when rolled into a thread approximately 1/8 in. in diameter. (2) The water content corresponding to an arbitrary limit between the plastic and semisolid consistency states of a soil. Liquid Limit: (1) The water content at which a pat of soil, cut by a groove of standard dimensions, will flow together for a distance of 1/2 in. under the impact of 25 drops by a standard liquid limits device. (2) The water content corresponding to an arbitrary limit between the liquid and plastic consistency states of a soil. The Plasticity Index (PI) is determined by the numerical difference between the Liquid and Plastic Limits.

Apparatus v Mixing bowl: porcelain bowl 4 to 5 in. diameter v Rubber-tipped pestle and mortar (bowl) v Spatula: having a flexible blade approximately 3 in. long by 1/2 in. to 3/4 in. wide v Liquid limits device: a mechanical device consisting of a brass bowl with a hard rubber base, as shown in Figure 3-8 v Grooving tool: a combination grooving tool and height calibration gauge, as depicted in Figure 3-8, or refer to ASTM for an alternative flat style; many laboratory technicians feel that the rounded grooving tool—as shown in this text—is easier to use and may ‘tear’ the soil less than the flat grooving tool. v Drying containers: small containers about 1½ in. diameter, tared and numbered with indelible ink v Scale: accurate to 0.01 g v Ground glass plate: at least 12 in. square by 3/8 in. thick. v Sieve: No. 40 (425 μm)

45

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Chapter 3: Basic Laboratory Tests

Figure 3-8

Liquid Limits Testing Device

Preparation (Dry Method) Place a representative portion of the soil sample in a pan; allow it to air dry [or oven dry at 140 °F (60 °C) or less]. Next, break up the sample with a pestle in the mortar, and then pass the material through a No. 40 sieve. Weigh out =200 g of the specimen.

Procedure Place the weighed-out material into the porcelain mixing bowl and add 10 to 15ml of water. Mix in the water by using the spatula. Continue to mix, knead, and chop the sample while adding water as needed to bring the soil consistency to somewhere between the liquid and plastic limits; the soil should have a consistency similar to stiff modeling clay at this point. Break off a portion of the sample for the plastic limit test (approximately 20 g) and place it in an airtight bag or sealed plastic container to cure. Seal the remaining portion of the sample (approximately 175 g) in another airtight container. This portion will be used for the liquid limit test. Let both of

47

Chapter 3: Basic Laboratory Tests

these samples cure for a minimum of 16 hours. This will ensure that the water and soil particles are thoroughly blended together. Plastic Limit Remove half of the soil to be used for the plastic limit test from the container. Squeeze and mold the sample into an oblong mass, then place the soil mass on the glass plate. Use your fingers to roll the soil mass into a thread with a diameter of ⅛in. Pick up the thread and remold it into an oblong shape. Again, roll it into a thread ⅛in. diameter. Repeat this operation until the soil can no longer be rolled into any ⅛in. diameter threads but crumbles and cracks apart. Tip: If the sample is overly wet, rolling it on paper (with non-removable fibers) will help to absorb excess moisture. Immediately place the crumbled soil into a container and record the weight on the test sheet (Figure 3-10). Place the sample in the oven to dry at 230 °F (110 °C). Repeat this procedure for the remaining half of the sample. Again, place the crumbled soil into a container, weigh it, and place it in the oven to dry. The point at which the soil breaks apart and can no longer be rolled into a 1/8 in. thread is the plastic limit. Any sample that cannot be rolled into a 1/8 in. thread (no matter how the moisture is adjusted) should be considered non-plastic. Liquid Limit Step 1 Remove from the container the soil to be used for the liquid limit test. Add 3 to 5 ml of water and thoroughly mix by chopping, mixing, and kneading. Step 2 Place a portion of the soil in the liquid limits device brass bowl (Figure 3-8). Using a spatula, level the soil pat (without trapping any air bubbles in the mass) to a thickness of one centimeter. Using the grooving tool, cut a groove through the center of the soil pat as shown in Figure 3-9.

Figure 3-9

(Liquid Limit Test in Progress) (A) Soil pat in the brass bowl, ready for test. (B) Soil pat divided by the grooving tool. (C) Soil pat has flowed closed after the test from the impact of the brass bowl dropping against the hard rubber base.

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Chapter 3: Basic Laboratory Tests

Tip: When using the grooving tool, try to avoid tearing the sample; it is helpful to use a rolling motion while cutting the groove. Step 3 Turn the crank on the liquid limits device at a steady speed (about two drops per second) until the soil mass has flowed together to create a 1/2 in. closure. If a closure zone of ½in. is achieved at between 25 and 35 drops, proceed to Step 4. If more than 35 drops are necessary to obtain the ½in. area of closure, add more moisture and remix, as described in step 1. If the sample requires fewer than 25 blows for proper closure, then the sample is too wet. In that case continue to mix the sample until it has sufficiently dried back. Do not add more soil to help dry the sample back (or oven dry); adding dry soil or oven drying will create an inconsistently mixed sample (from lack of curing), thus putting the accuracy of the test in question. Repeat Steps 1 through 3 until the proper closure is achieved at between 25 and 35 blows, then proceed to Step 4. Step 4 Using the spatula, immediately remove a portion of the soil pat (approximately 10 to 15 g) from the 1/2 in. closure zone. Place the sample in a numbered container. Record the weight and the number of drops on the test sheet, and then place the sample in the oven to dry at 230 °F (110 °C). Repeat Steps 1 through 4 as needed to obtain two more samples: one sample closing between 20 and 30 drops and one sample obtained from between 15 and 25 drops. Each successive point must take less drops to close; this will allow three liquid limit samples to be plotted accurately as points on a graph. Step 5 Weigh all of the plastic and liquid limit samples that have been dried in the oven. Record all weights on the test sheet.

Calculations and Graph Plotting 1. Percent Moisture = (W/D) × 100 Where: (W) weight of water = wet weight of soil and container – dry weight of soil and container (D) weight of dry soil = dry weight of soil and container – weight of container 2. Plastic Limit (PL) = The average of the two Plastic Limit moisture percent results from the test sheet 3. Liquid Limit (LL): Plot the percent moisture versus the number of drops for each of the three liquid limit moisture results on the Liquid Limit Graph (lower graph on Figure 3-11). Next draw an average straight line through the three points.

49

Chapter 3: Basic Laboratory Tests

Figure 3-10

Figure 3-11

Plastic and Liquid Limit, Test Sheet, and Graph

Figure 3-12

Soil Classification Graphic Chart (PI versus LL)

The graph location at which the sloped line intersects the 25-drop line and the corresponding moisture percent at the left side of the graph = the Liquid Limit.

50

Chapter 3: Basic Laboratory Tests

4. Plasticity Index (PI): PI = LL – PL 5. Classification: Using the graph on Figure 3-12, plot the Liquid Limit against the Plasticity Index to determine the USCS (soil type) of the material tested.

Chapter 3 Questions 1. Which type of Proctor uses a 10 lb hammer and an 18 in. drop?

(a) (b) (c)

The original Proctor proposed by R. R. Proctor The modified Proctor (ASTM D1557) The standard Proctor (ASTM D698)

2. ASTM D1557 method A uses which screen to pass material through?

(a) (b) (c)

NO. 200 NO. 40 NO. 4

3. Optimum moisture is the point that:

(a) (b) (c) (d)

A sandy soil should be screened across the NO. 4 sieve A fine-grained soil becomes liquid Soil will compact best in both the field and laboratory No more water can be retained in a soil

4. Sodium hexametaphosphate is used to:

(a) (b) (c) (d)

Remove dry soil from dirty sieves Deflocculate fine soil during a hydrometer test During a Proctor test, to help reach optimum moisture None of the above

5. The hydrometer analysis is used to determine the particle-size distribution of:

(a) (b) (c) (c)

Sand, clay, and silt Sand and colloids Material finer than the NO. 200 sieve None of the above

6. Hydrometer readings should always be taken at the top of the meniscus.

(a) (b)

True False

4 Field Density Tests Field density tests (compaction tests) are used to measure the amount of moisture and the percent compaction of the material placed during backfill or grading operations. Both the sand cone and nuclear gauge tests measure the moisture content and degree of compaction—which are expressed as a percentage of the optimum moisture and maximum density, respectively. The percent moisture indicates the average amount of water at a specific location. The percent compaction is typically defined by the in-place dry density of a soil at a certain location as compared with the laboratory maximum dry density of that same soil type (determined by the modified Proctor test described in Chapter 3).

Importance of Field Density Tests Density tests are taken wherever fill is placed for structural support or road base to help confirm that the soil is being adequately moisture conditioned and densified per the project specifications. Poorly compacted material placed beneath footing or slab areas can lead to settlement. Soft or loose soil can cause wall and ceiling cracks, differential settlement of floors, and windows or doors not opening or sliding properly. Improper moisture conditioning of expansive clayey soil can result in cracked, uplifted, separated, or tilted floor slabs and footings. Density testing of trench backfill is also required. Too often the technician is not on site full-time during the placement of trench backfill. Therefore, density tests must be taken at a number of different locations and depths within the trench to help confirm that the trench soils have been sufficiently compacted. Improper compaction of trench backfill can cause settlement in streets (potholes), lead to cracked sidewalks, and even break utility lines.

Planning One vital step prior to taking a field density test is to obtain a bulk sample to transport to the lab in order to perform a maximum density test (Proctor or curve). Without having a curve (maximum density value) to compare with your field density test data, it is not possible to give an immediate percent compaction. Many projects have been held up waiting for the curve to be pounded in the

52

Chapter 4: Field Density Tests

lab, because no maximum density test had been completed prior to the technician arriving on-site. Good teamwork and planning by the project manager (usually an engineer or geologist), the technician, and the contractor will keep a project from being delayed due to not having proper Proctor results available. A project should have curve samples that were obtained during the site investigation and are presented in the project geotechnical report. Often, the technician may be called to a site where curve samples have not yet been taken, or during project grading when a new soil type has been exposed. Either situation can cause unexpected delays. Yet, each can be avoided by careful scheduling and picking up curve samples in advance.

Curve Sampling There must be a curve sample for each soil type that is being compacted by the contractor. The sample(s) that you choose must be representative of the material being compacted in each location by the contractor. On small projects, there may be only one or two curves, such as a curve for the subgrade (SG) and another for the aggregate base (AB). On larger projects the curve list may include dozens of Proctors. Therefore, complete material/sample information is critical. Each sample should be placed in a large sealed plastic bag or in a lidded bucket. The bag or container should be labeled with the following information: Basic Information: Project Name, Project Number, Date, and Sample Number Classification: A thorough Soil Description, including Color and USCS (as discussed in Chapter 1) Sample Location: Label as “Native” if from the on-site and indicate where the sample was obtained; label as “Import” if the material was trucked in and clearly note where the material originated from. It is important that the field technician and the lab technician include the same information—always. Should it be necessary to change any information, clear communication must occur between the field and lab techs. If this standard procedure is not followed, the field technician is not able to choose the correct Proctor to compare to when performing a field density test; thus, invalidating the field test result! When choosing a curve, always choose the correct Proctor by matching the soil description in the field with the soil description of the Proctor from the project list. Never choose a Proctor because the maximum density ‘looks right’ or will ‘make the test pass’.

53

54

Chapter 4: Field Density Tests

Commonly Used Field Density Tests This chapter describes two of the most commonly used field density test methods; the sand cone test and the nuclear gauge test. The procedures described in this chapter to perform the sand cone and nuclear gauge density tests are generally consistent with ASTM test methods D1556 and D6938, respectively. However, it is recommended that current ASTM or other project specifications be understood and observed. The sand cone—like the nuclear gauge—is a tool used to help technicians confirm their observations and form opinions about the moisture and density of the material being tested. Relying on their experience and judgment, technicians should watch for soil conditions that may influence test results.

Sand Cone Test The sand cone has been widely used for many years to determine in-place field density. Although the sand cone has proven quite reliable in most soil conditions, the nuclear gauge density test is becoming the test of choice. Due in part to the slower test results of the sand cone as well as the bulkiness of the equipment (sand, scales, buckets, etc.), most testing agencies are now using the nuclear gauge in lieu of the sand cone. Nevertheless, the sand cone test is still used by many geotechnical firms, sometimes as the preferred method for forensic studies (legal investigations to determine why a structure may have failed), as a referee method, or simply because the equipment is less expensive.

Overview The dry density of the soil can be calculated by digging a hole, weighing the removed soil, and then pouring a measured amount of sand from the sand cone jar into the hole. This dry density is then divided into the maximum density of

Figure 4-1

Nuclear Gauge and Sand Cone

55

Chapter 4: Field Density Tests

Figure 4-2

Nuclear Gauge and Sand Cone Test Holes

the soil (from the laboratory Proctor) to determine the percent compaction of the fill placed.

Apparatus v Sand Cone: Aluminum funnel and glass or plastic jar (with plastic being preferred) v Aluminum Base Plate v Bucket or container: To hold the soil removed from the hole (and help carry tools) v Scales: 1-kg scale accurate to 0.1 g and 20 kg scale accurate to approximately 1 g v Camp Stove or Oven: For moisture burn-out v Pan or Container: For moisture sample v Digging Tools: Scoop or large spoon, screwdriver or chisel, paint brush (and any other tools helpful in digging a test hole) v No. 20 or No. 30 Silica Sand: For which the unit weight is pre-calibrated (or refer to ASTM 1556.A2)

Plate and Cone Calibration Prior to performing the actual sand cone test, the metal cone and plate must be calibrated as a set. This is because slight variations in either the cone (such as a minor dent) or the plate (how the cone seats into the plate, and inner cone lip thickness) will effect how much sand weight must be deducted to allow for only the volume of sand remaining in the hole. Each cone and plate must be used as a set for consistency in calibration. Remember to number your cone and plate set. A cone and plate set should be

56

Chapter 4: Field Density Tests

DIAGRAM 4-3

Sand Cone Apparatus

calibrated with each new batch of sand, and always if the cone or plate appear to be dented or damaged. To calibrate your set, fill the sand cone jar with silica sand, and then weigh the jar filled with the sand, (leaving about ½in. space from the jar top is a reasonable sand fill level). With the aluminum base plate on a horizontal and flat surface, seat the cone into the plate. Next, turn the valve on, allowing the sand to flow until it has completely stopped. Now re-weigh the sand cone with remaining sand and record the weight. Repeat this procedure two more times. For each of the three times, calculate the weight of sand that was used. Finally, total the three weights of sand used, then divide them by 3 to obtain the average weight of sand to fill your cone and plate set. Write this average weight on your cone, so it is easy to refer to during each test. This average weight of sand to fill your cone and plate will be recorded each time when calculating sand cone density test results. (Refer to No. 4 on the “sand cone test data sheet,” Figure 4-6)

57

Chapter 4: Field Density Tests

Procedure (follow ‘Steps of the Sand Cone Test’, Figure 4-5) Step 1 Fill the sand cone jar with silica sand, weigh it, and then record the weight (Line No. 1 on the sand cone test data sheet). Screw the cone onto the jar; check that the valve is in the closed position. Step 2 Carry the sand cone, base plate, bucket, and digging tools to the area to be tested. Level the area using a flathead shovel, or have the contractor cut a level test location with a dozer, blade, or other equipment. Place the base plate on the flat surface. Tip: If the contractor digs a test hole for you using a backhoe, do not allow the operator to fill in or pat down the teeth marks left by the digging action of the bucket teeth, or your density test will not accurately reflect the trench backfill material below. With a flathead shovel, remove the ridges left by the bucket teeth (or compactor feet imprints), then set your plate (or nuclear gauge) on the remaining undisturbed flat surface. Step 3 Using a scoop, spoon, or other suitable digging tool, dig a hole 4 to 6 in. deep using the base plate as a guide. Make sure that all the material removed from the hole is placed into the bucket. Any soil that has fallen onto the base plate during the digging process—and cannot easily be put into the bucket—should be swept back into the test hole with a brush, and then patted into place with your hand.

Figure 4-4

Author Taking a Sand Cone Test

58

Chapter 4: Field Density Tests

Figure 4-5

Sand Cone Test Procedures Step 4 Place the sand cone onto the base plate over the hole. Make sure the funnel is properly seated into the groove of the base plate. Open the valve and wait for the sand to fill the hole and cone completely. Do not tap the cone or funnel during the test. Ensure that there is no vibratory equipment working close enough to vibrate the sand, which could lower the test result. The reason for these aforementioned concerns is because more sand would vibrate into the hole than from gravity flow only. After the sand has completely stopped flowing, turn the valve off and remove the sand cone from the hole. Steps 5 and 6 Weigh both the sand cone and the bucket of soil. Insert the weight of the bucket and soil (line No. 7) and the weight of remaining sand and cone (No. 2) on the data sheet.

59

Chapter 4: Field Density Tests

Figure 4-6

Sand Cone Test Data Sheet

60

Chapter 4: Field Density Tests

Remove about 250 to 300 g of material from the bucket and place it in a pan or container for the moisture burn-out. Weigh the sample and record the value as the wet weight and pan (No. 11). When the sample has completely dried, obtain a weight and insert the value as the weight of dry soil and tare (No. 12) on the data sheet.

Calculations For both the in-place moisture content and dry density of the soil, calculations can now be made (see steps listed in Figure 4-6 for calculations). Sand Cone Test Biases: Some soils—when placed in an overoptimum moisture condition, or when considerable “pumping” is present—may be hard to test accurately with a sand cone. This is because after a test hole is dug in these wetter soils, and before the silica sand can fill the hole, the hole may close in enough to give a false density (higher than actual) result. A nuclear gauge can give a more dependable reading for these soil conditions.

Nuclear Gauge Test The nuclear gauge is now widely accepted as an accurate and rapid method for taking moisture and density tests in the field. Unlike the sand cone test, in which results take about 20 minutes or more to complete (when done in the field); a nuclear gauge can calculate results within a minute or less. In addition, test data can be stored in the gauge’s memory, then recalled or downloaded later. Nuclear gauges typically use two sources of radioactive material: cesium-137 and americium-241:beryllium. The cesium is steel encapsulated at the tip of the “source rod,” and the americium is permanently located inside near the base of the gauge. The cesium is the source of gamma rays (used for density readings) and americium is a neutron emitter (for moisture readings).

Nuclear Gauge Safety

61

Chapter 4: Field Density Tests

When used with care, the nuclear gauge can be safe. However, it is important not to become desensitized to the dangers of radioactive material just because the radiation cannot be seen or immediately felt. Radiation exposure is cumulative, but it can be minimized by limiting the time and increasing the distance from the gauge during usage. Do not place the nuclear gauge near the driver or passenger compartments (during transport or while parked), and never sit or do paperwork on the truck tailgate near the nuclear gauge. Prior to using the nuclear gauge, an approved training course must be completed by the user. All current federal, state, and local regulations must be followed while using radioactive test equipment. The following are a few minimum safety guidelines to be adhered to when using nuclear gauges: Always wear your dosimeter badge when near a nuclear gauge. Do not allow unqualified personnel to use a gauge. When not taking a test, lock the source rod and put the gauge away in its’ locked storage container (Figure 4-7). When transporting a nuclear gauge—even short distances around a job site— the gauge should be locked in its storage box and the box locked securely to the vehicle. Use common sense; for instance, do not lean on the tailgate of a truck next to where a nuclear gauge is stored, thus allowing yourself to be exposed unnecessarily. Never touch, look at, or stand near an unshielded source rod. Should your gauge not be working properly (such as the probe not sliding smoothly), or if you have noticed any damage to the gauge, or have any other concerns, contact your Radiation Safety Officer (RSO) immediately.

Figure 4-7

Nuclear Gauge Stored in Box when not in use This type of storage box can lay down to lock in the level position during transportation and will easily tilt into the upright position (as shown in photo) for removing the gauge.

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Chapter 4: Field Density Tests

Taking a Test To perform a density test with a nuclear gauge, a flat surface must be prepared (Figure 4-8). One advantage of the nuclear gauge is that it allows you to take a test on a slope face; the surface must be flat, but not necessarily horizontal. In contrast, a sand cone test must always be taken on a flat and horizontal surface. Another advantage is that a nuclear gauge can give wet density, dry density, and moisture results concurrently; no moisture “burn-out” is needed as with the sand cone test—this allows for immediate density and compaction calculations. The appropriate laboratory maximum densities may be stored in the gauge memory, reducing the calculation to a simple push of keypad buttons. Density may be taken with the gauge in either the “backscatter” position (in which the source rod does not penetrate the ground surface) or in the ‘direct transmission’ mode in which the source is inserted to a desired test depth (up to 12 in. with some model gauges). The backscatter method generally tests the material within approximately 4 in. of the surface. Taking a test in the backscatter mode may be advantageous on relatively thin (5 in. or less) thickness of aggregate baserock or other granular noncohesive soils. Often times the aforementioned soils may cave in when the drive pin is removed in preparation for direct transmission testing. The backscatter mode is also commonly used when testing asphalt, for which typically only wet density readings are desired.

Figure 4-8

Test Location Scraped Smooth The steel plate attached in front of the compactor wheel was used by the excavator operator to dig a flat surface for the nuclear gauge test. Not all excavator or backhoes have a plate attachment; the technician must then use a flat-head shovel to level a test area.

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Chapter 4: Field Density Tests

Figure 4-9

Steps of Taking a Nuclear Gauge Test

The direct transmission method (Figure 4-9, Step 4) can be used in many different soil conditions, including trench backfill and testing fill 4 to 12 in. thick. With experience, a technician will learn how best to best utilize the nuclear gauge, depending on materials and locations being tested.

Nuclear Gauge Test Biases: Certain minerals, such as gypsum or diatomaceous and other soils, may cause the neutrons (emitted by the americium-241:beryllium source) to be absorbed in a manner that may cause the gauge to read a different moisture content than the

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material actually contains. To adjust for this anomaly, a sample of the material in question should be dried in the laboratory for moisture content. The difference between the field and lab moisture can be used as a reference to “offset” the gauge to read accurate moisture for the specific material being tested. This offset value must be made for each specific gauge. Another case in which the moisture may read improperly is while testing trench backfill. Because of the “sidewall scatter” effect of the neutrons, the moisture reading may be higher than the actual moisture content. To adjust for this inaccuracy, the gauge being used may be standardized in the trench (per manufacturer’s instructions) to account for sidewall scatter. Typically, if the trench walls are about three feet from the gauge, no significant sidewall effect occurs. Step 1: Place the nuclear gauge on the reference (calibration) block. (Refer to Figure 4-9.) Calibrate according to the instruction manual. Record the readings. Step 2: Place the scraper plate on a flat surface free of surface voids. The scraper may be used to level the surface. Step 3: Using the scraper plate as a guide, drive the drill rod into the ground to at least 2 in. deeper than the depth to test, and then remove the rod. Step 4: Set the gauge over the hole and insert the source rod into the test position, making sure that the handle is clicked into position. Take the test according to the instruction manual and then record the readings.

Chapter 4 Questions 1. The sand cone test uses No. 10 silica sand:

(a) (b)

True False

2. The depth of the hole dug for the sand cone test should be:

(a) (b) (c) (d)

2 to 4 in. 4 to 6 in. 3 to 5 in. None of the above

3. After the sand has stopped flowing from the sand cone jar during a test, you should firmly tap the jar:

(a) (b)

True False

4. The neutron source of the nuclear gauge is depleted Uranium 238 and is relatively harmless:

(a) (b)

True False

Chapter 4: Field Density Tests

5.

A sand cone test may be performed on a sloped surface:

(a) (b) 6.

A nuclear gauge test may be performed on a sloped surface:

(a) (b) 7.

True False

As long as the nuclear gauge is locked in its storage box at the rear of a pick-up truck, it is OK to sit on the tailgate near the gauge.

(a) (b) 8.

True False

True False

Which of the following soils, or test situations, may bias or cause the gauge to give an inaccurate moisture result?

(a) (b) (c) (d) (e)

When testing gypsiferous soil When testing diatomaceous soil When testing backfill in a 30 in. wide trench All of the above None of the above

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5 Jobsite Soil Construction A main responsibility of the soil technician or inspector is to help confirm that the recommendations presented in the geotechnical report are implemented in the field during grading and other construction processes. To properly interpret the recommendations, field staff must be familiar with soil engineering terminology. Both trainees and more experienced field personnel can use the glossary in Appendix C as a quick reference.

Project Preparation Many grading requirements in the geotechnical report are common practice— such as removing debris, stockpiles, and the stripping of vegetation. Minimum recommendations typically include the removal of unacceptable material including: organic, highly expansive soil, undocumented fill, porous, collapsible, loose, or soft soils. They also include preparation for fill placement over the exposed soils, including: scarification, moisture conditioning, and compaction. Each soil report refers to specific site conditions and must be read carefully. Too often, technicians become overconfident and neglect to read the geotechnical report closely, thus overlooking a recommendation that may be unusual during normal grading operations. It is good practice for the technician to prepare for new projects by highlighting specific recommendations in the geotechnical report, including the following: Depth of removals: Cut or over-excavation (OX); Cut and fill limits should also be highlighted on the grading plans (red for cut/blue for fill) Type of materials to be removed: Loose, soft, porous, expansive, or highly cemented soils Degree of compaction: Recommended compaction may vary with soil conditions or proposed structure type Moisture limits: To be targeted during compaction (i.e., near optimum, 2% to 4% over optimum, etc.) Placement of specific soil or material: Oversized material, expansive clays, gypsiferous soils, and other unique materials All other project-specific recommendations

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If there are no records of the fill having been properly compacted, it should be completely removed—or addressed by other engineering means—before placing foundations or new fill. Pay careful attention to the type of soils encountered in the geotechnical report through close review of the boring and/or trench logs. Compare materials exposed during excavation and site grading with those described in the soil report. Any discrepancy should be discussed with the project engineer immediately.

Flatland Projects When grading mostly flat sites—after removal of unacceptable material—the degree of compaction and percent moisture content are usually the most critical factors. However, prior to placing any fill, the existing ground surface must be prepared by scarification (typically 6in. deep), moisture conditioned, and then compacted. When placing expansive soils, the moisture content of the material is as important as the degree of compaction. Many silty and clayey soils are extremely sensitive to moisture changes. In some silty soils (diatomaceous soils, for example), a variation of only a few percent in water content could change the soil’s dry density by as much as 5 or 10 lb/ft3 during compaction. Also, many plastic soils increase in volume (expand) with added moisture (and, conversely, shrink when dried back); therefore it is standard practice to place expansive soils in a slightly over-optimum condition, and often at a lower degree of compaction—compared with non-expansive soils—to help limit expansion potential. Even sandy and silty non-cohesive soils generally compact better when placed at or slightly above optimum, thus lubricating the particles—as well as helping to mitigate any future settlement or consolidation caused by increases in moisture from landscape watering or heavy rains.

Road Construction Performance of the final road surface is based on the “Road Section:—the asphalt, aggregate base, and the subgrade. Together these three materials make up the Road Section.

Preparation and Compaction The first step is the preparation of the existing ground surface to create a compact and stable subgrade (SG). When an area must be cut down to reach the proposed finish subgrade elevation, rocks and/or soft pockets are often exposed, and then removed. To create a homogeneous subgrade, it is important to prepare the cut (or fill) subgrade surface (prior to placing aggregate base) by scarifying, removing cobbles and larger rock, moisture conditioning, and then

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compacting. Improperly prepared subgrade is often the cause of potholes, cracks, and areas of settling or uneven pavement. During the grading of subgrade and aggregate base course for road construction it is important not only to test for compaction, but also to observe the actions of the compaction equipment on the material during the compaction process. For instance, although a density test taken on the subgrade may indicate that the moisture content of the material is only a few percentage points over optimum (which is generally desirable within building areas), you may notice that the subgrade soil is moving—pumping or rolling—beneath the compaction equipment. Soft and pumping (yielding) soils are not acceptable. The surface must be firm and unyielding prior to paving. Soil that deflects or moves is detrimental to pavement. Note: Before accepting a subgrade or aggregate base as finished, the surface should be ‘proof rolled’. A fully loaded water truck works well for proof rolling. Beware that some contractors may try to proof roll with a partially filled truck! As you walk along during proof rolling, paint out locations to be re-worked or otherwise stabilized. It is important to walk next to the compaction equipment during the final compaction of both the finished subgrade and aggregate base surfaces to closely observe the material for any movement or deflection beneath the tires or rollers. Often remixing and/or drying back of the material to bring it closer to optimum, followed by recompaction, will stabilize the subgrade. However, sometimes overly wet or soft soils need to be excavated and replaced with compacted aggregate base or other acceptable material. For more severe cases of unstable subgrade, stabilization may first include the placement of a woven geotextile fabric or geogrid, overlain by compacted aggregate base (Figure 5-1). Tip: Woven stabilization fabrics work quite well when used properly. However, all too often the fabrics are placed improperly and are not overlapped enough, or not loaded down with sufficient aggregate base or other material. A minimum overlap is usually 18 to 24 in. Experience has shown that placement of a layer of 18 in. of aggregate base is the minimum necessary for long-term stabilization results. The technician should also watch the finished baserock surface for any nesting or segregation of the material. Sometimes surface areas or pockets containing mostly gravel with few or no fines may occur. This segregation (nesting) may be due in part to excessive rubber-tire traffic allowed on the base rock prior to paving. Surface areas that are not homogeneous, or fail to meet gradation standards, should be remixed and re-compacted or even replaced. Density testing of aggregate base can sometimes be tricky. If a baserock section is relatively thin (5 in. or less) better test results may be obtained by using the ‘backscatter’ mode of a nuclear gauge. Many times, when the drill rod is being driven in (to prepare for a “direct transmission” test), the baserock may move

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and become too disturbed to accurately test. Using the backscatter mode will not disturb the aggregate base. Silica sand (or aggregate base fines) may be used to fill in any minor surface voids, thus providing a more reliable test. Through experience, a technician will develop a better feel for which test method works best in a specific situation.

Figure 5-1

(a) Excavatethe unstable soil, then smooth the bottom. Cut the woven geotextile fabric so it overlaps the edges and any fabric joints a minimum of 24 in., then nail the fabric to the walls to hold the fabric during AB placement, this is critical: the fabric must stretch snugly.

(b) Place a lift of AB (~12 in.) and moderately compact

(c) Each successive lift of aggregate base at may now be given more compactive effort. Using a jumping jackor a large vibratory plate for compacting the perimeterswill help (a small vibra-plate compactor is too light and should not be allowed).

(d) Finally, finishing the upper 6 to 8 in. to least 95%

into place. An excavator wheel with cleats, or for large areas a sheepsfoot roller will work well. Roll the full lift, including edges. This will help to 'lock and stretch' the woven geotextile fabric into place.

of ASTM D1557 will finish the stabilization job. Both the inside and the perimeter must be equally well compacted.

(e) The edges of the existing asphalt were tacked with SS-1 oil (asphalt emulsion) prior to placing the first 2½" lift of Hot Mix Asphalt (HMA). After the HMA was compacted with a vibratory steel drum roller, the first lift was let to cool down to 115 ºF. Then the final 2 ½ in. lift of HMA was placed and compacted. Follow-up inspections to this and similarly stabilized roads have shown that the areas have performed well, typically with no observable settlement.

Stabilizing Road Subgrade with Woven Geotextile Fabric (For this application, a Mirafi 600X Woven Geotextile was used.)

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Hillside Grading On hillside projects, the first step—as always—is to become familiar with the project by reviewing the geotechnical report, and then highlighting projectspecific recommendations. The approved grading plans should be reviewed, taking note of important existing surface features, such as: canyons, landslides, steep slopes, seeps, and rock outcrops. In addition, note planned earthwork features to be created during grading, including: pad construction, slope stabilizations, cuts and fills, stormwater protection, and LID features. It is important that the technician coordinate hillside testing and inspection with the project geologist or geotechnical engineer.

Areas of concern during hillside grading: Cleanout of soft or otherwise unacceptable materials from swales, canyon sides and bottoms (Figure 5-2), previously farmed areas, existing stockpiles and all unapproved fill Slide removals, slope stabilizations or buttress fills, including keyway construction and back drain placement (Figure 5-2 and 5-3) Proper benching into competent material as fill is placed against existing slope or canyon sides (Figure 5-2 and 5-3) Cut slope faces to observe for loose material, seeps, slide planes, or out-ofslope bedding planes Fill slope faces for proper compaction, either by compacting completely over the outer edge during placement, or overbuilding and then trimming back into compacted material Areas in which rocks have been blasted (Figure 5-6, a and b), observe closely to help determine that all significantly fractured material has been removed. Utility trenches often must be placed through cemented areas or bedrock, and hydro-hammer or rock saw attachments may be needed to cut trenches. If trenches are excavated through areas of ground water or seasonal wet zones, pipe bedding should be enveloped in non-woven filter fabric. In these wet zones, often-times check dams are placed every few hundred feet with solid pipe outlets are used to relieve hydrostatic buildup. Other methods, such as backfilling the trenches with 2½ sack cement/sand slurry can work well. Placement of drainage systems in canyons and buttress fills. The key should be excavated into competent material (often bedrock), tilting into the slope 2% to 5%, and made long enough to support the fill slope, while allowing enough width for the compaction equipment to completely overlap during keyway backfill and compaction. Benches should always be placed level and excavated into suitably dense material. Benches are typically placed 2 ft horizontally into the existing material, and at each 2 ft vertical thickness of compacted fill.

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Figure 5-2

Canyon Fill Keep in mind that a Key (or keyway) is always placed at the toe of a fill slope; while a Bench (or benching) is performed as fill is placed against an existing slope.

Figure 5-3

Buttress Fill Figures 5-4 and 5-5 show a drainage system placed along the bottom of a canyon in Lake Elsinore, California. During grading, seepage was observed near the top of the canyon. The canyon was cleaned out, a slot was cut, and a “burrito”-type subdrain was installed (similar as shown in Figure 5-2).

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PHOTO 5-4

Canyon Subdrain being placed This drain was formed by placing 6 in. of 3/4 in. size crushed rock atop a non-woven geotextile filter fabric, over which a 6 in. perforated pipe was laid (perforations facing downward), and then finally covered with 6 in. more 3/4 in. rock—with the fabric wrapped over the top to completely envelop the rock and pipe. A 40 ft length of solid pipe was connected at the outlet end of the drain at the base of the canyon fill. Engineered fill was subsequently placed in the canyon, benching the canyon sides as the fill was placed in level lifts.

Rock Fill (Oversize Material) Placement Increase in population has created the need for more housing and has led to construction into plots of land that was previously deemed unbuildable, oftentimes owing to the hilly and rocky nature of the landscape. It is now common practice to place homes and industrial complexes over “rock fills.” Proper placement and observation of these fills are mandatory to help minimize unacceptable settlement that can be caused by nesting, voids, or lack of adequate densification. A fill can be considered oversized (or rock fill) when more than 30% of the material (by weight) is larger than ¾in. size, and therefore according to ASTM standards, an ASTM D1557 Proctor cannot be performed on the material. Because rocks do not tend to fit together flush when placed by themselves in a fill, it is critical that the matrix material (soil and material finer than 3/4 in.) is able to infill the voids between the rocks. For this reason, predominantly granular material (when available) is best to use as matrix soil. The geotechnical report will often indicate a criteria for the matrix soil, such as an SE (sand equivalency—ASTM D2419) of 32 or greater or a nonplastic PI (ASTM D4318). The report will also describe acceptable placement techniques and often require full-time observation by an engineering firm during oversized material placement (rock fill). Refer to Figure 5-6, photo D for an acceptable rock fill placement method.

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Figure 5-5

Canyon Subdrain in place This particular subdrain continues to run, nearly year-round.

Observation During Rock Fill Placement It is not accurate to take density tests in a rock fill (with the nuclear gauge or 6 in. sand cone). Therefore, it is important that full-time observation be made during placement. While a rock fill is being placed, the following concerns should be addressed: Is the matrix material granular enough? Is the type of compaction equipment used heavy enough? Is adequate water being added to help lubricate the matrix soil into the voids between the rocks during compaction? Often a water content criterion is recommended, such as 2% to 8% over optimum for the matrix soil. Placement of rock fill may be performed by pushing the rock and matrix material out as a blanket-type fill, with a water hose or truck continually wetting the material as it is spread, and then the compaction equipment rolling over the top. Placing the rocks in windrows and pushing soil into the

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Figure 5-6

(a) This hard granitic formation could not be broken or excavated with conventional grading equipment.

(b) Holes were bored, packed with explosives, and then blasted to pre-determined depths.

(c) The rock was excavated with large dozers down to solid non-disturbed material. Remaining large boulders were then broken down into easier to handle sizes by an excavator with a rock hammer (hydro-hammer) attachment.

(d) The oversized material (>3/4 in. rocks and boulders) was then placed in shallow basins. Dozers and loaders spaced the material out, and then relatively clean sand was flooded and compacted over/around the large material.

Blasting of Rock and Placement of Oversize Material

Chapter 5: Jobsite Soil Construction

rock from the sides is generally not an acceptable method; compaction is harder to achieve by pushing from the side (as compared to an applied load from the weight of the equipment on top), and the rock is more likely to nest when placed in windrows. Help confirm your observations by having the contractor excavate an observation pit into each compacted lift of rock fill. Closely observe that the contact between the rocks and the matrix material appears well densified— voids or loose material cannot be present—and moisture content is consistent throughout the matrix soil. Re-work areas of rock fill that do not appear sufficiently dense. These areas must be moisture conditioned, re-mixed, and re-compacted. Upon completion of the re-worked area, another observation pit should be excavated and observed.

Cut, Fill, and Transition Pads Another extremely important step is to “daylight” the grading plans. This involves highlighting the elevation contours across the site to emphasize the cut/fill contacts (e.g., highlighting cut areas in red, and fill areas in blue). Tracing the daylight line (cut/fill contact) across building pads is particularly important to determine whether the lot should be treated in a special manner due to a transition contact. Differential support conditions are a concern where foundations span cut and fill soils transitions, or when foundations cross native rock and engineered fill. Review of the geotechnical report will indicate whether over-excavation or other methods (extra steel placement, use of a floating or post tensioned slab, etc.) are necessary to help mitigate differential settlement.

Deep Foundations Driven piles, drilled piers, and poured caisson shafts all require special inspection. Observation of this work is coordinated with the project engineer. Although shallow foundations may depend wholly on the bearing material, deeper foundations may gain support from friction and/or bearing. Therefore, during the drilling of shafts for deeper foundations it is critical to log the soil and rock strata accurately.

Some important areas of observation: Log the strata of the material as it is drilled into—confirm that it matches the reported conditions. If different soil conditions are observed, inform the project engineer or geologist immediately. The straightness of the excavated shaft should be checked; it should be vertical with no overhanging material. Ensure that the top elevation and tip depth are per plan. Measure the hole diameter; a variation from planned size will affect the volume of concrete necessary, and possibly the steel cage diameter.

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Check the cleanliness of the hole; for caving, water seepage, debris, or other unusual conditions. Note the time and date of completion; holes should only remain open a limited amount of time before placing steel and pouring concrete. (Check with the project specifications or the project engineer for time constraints). Confirm that steel size, spacing, and placement is correct; the steel cage must have proper clearance from the wall and bottom of the drilled shaft. Watch that the concrete is tremied to the bottom of the hole during the pour. Tip: If the lower portion of the open shaft is filled from seeping water, the bottom of the tremie hose can be plugged with a rubber or vinyl ball (like a dog or kid’s toy); the plugged tremie can then be lowered into the flooded hole without the possibility of filling up with water. With the tremie at the bottom, the concrete can be pumped from below the water through a dry hose, thus avoiding the risk of diluting the concrete. The ball will be forced out of the tremie nose by the concrete (often-times even floating to the top : : : to be re-used the next time!). Compare the theoretical volume with the actual volume of concrete placed. (Too much concrete may indicate a hole “blow-out,” whereas too little may indicate hole caving.)

Figure 5-7

Specialty Piles During February 2017, the Oroville Dam in California came close to a catastrophic failure. The State of California Water Resources, within a few months, began repair of both the main chute and emergency spillway. The drill rigs in Figure 5-7(A) photo are lined up working on a secant pile erosion cutoff wall about 1,000 ft downstream of the emergency spillway crest. The secant piles are now in place (as a cut-off wall) to help prevent scouring by swiftly moving water during any future overflow event. The piles are 36 in. diameter, ranging from about 35 to 65 ft deep, founded below the weathered bedrock.

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The rotary drill barrel [Figure 5-7(B)] with seven rotating cutting bits was used by the drilling contractor early in the project to drill through portions of unreinforced secant pile, and into the suitable bedrock formation. Other bits were used during the project based on the experience of the drilling contractor. Steel cages were set into the (alternated) secondary secant piles and poured with 2,500 psi concrete. The alternating un-reinforced and reinforced overlapping secant piles formed the new cut-off wall.

Figure 5-8

Helical Piles being placed At a sewer lift station in Northern California, soft upper soil was settling under the weight of a diesel fuel supply tank located next to the pump control building. The tank was temporarily lifted/moved; then a number of helical piles were drilled through the soft upper soil into lower denser soil. The steel helical piles were cut and left in place to create sound support for the subsequently poured concrete tank foundation and containment.

Shallow Foundations Technicians are often called on to observe concrete foundation excavations, including: footings, building slab, sidewalk, curb and gutter, driveway, and ADA ramp preparation, to name a few.

Usual areas of concern: Width and depth (or elevation) of the foundations. The width and depth of the footings and all concrete structures should also be measured to verify that they conform to the project plans. Density of the foundation bearing material, as well as the SG and AB for slab foundations. The bottom excavations for continuous and spread footings should be probed (with a hand probe) for loose or unsuitable material—prior to steel placement—and observed whether the footings are free of water and debris.

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Figure 5-9

Placement of Steel and Pouring Foundations Photo (A) shows a pad with steel improperly placed: the steel is laying on the slab sand, and the exterior footing has water in the bottom and grass appears to be growing from under the visqueen moisture barrier. Photo (B) shows a clean pad with dobies supporting the steel. The concrete is being vibrated during the pour as well. Pay special attention to footing bottom material; watch for porosity (compressible soil), compacted fill and native soil or bedrock contacts (cut/fill contact—creating potential differential settlement), clayey—possibly expansive soil, or other material changes that may affect structural support. Sometimes during grading the depth of over-excavation (OX) may not have been deep enough to remove pockets or layers of porous soil, or to rework cut/fill contacts. Clayey (potentially expansive) soil may need to be saturated well over optimum or treated in another manner prior to pouring concrete. Prior to placing steel and/or pouring concrete; all foundation bottoms must be free of loose material, water, vegetation, and debris (Figure 5-9). Steel for footings, slabs, and other concrete structures must never be touching the sides or bottoms of the excavations. Dobie blocks, stand-offs, or spacers should be tied to the steel to hold it in position. The space necessary for steel separation should be confirmed on the structural plans, or in the geotechnical report.

Retaining and Specialty Walls There are many types of retaining walls, with design determined not only by structural needs but also due to financial and even aesthetic reasons. Most retaining wall construction requires good bearing material at the wall base or footing. Similar to continuous footings, the wall footings should be founded in dense undisturbed soil, relatively unfractured rock, or compacted fill. Often, block retaining walls may be anchored by geogrid that is pinned between the

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blocks, with the geogrid extending and compacted a number of feet behind the wall. In all cases, the technician must take time to review the wall foundation recommendations from the geotechnical report, as well as studying the plan details. A few commonly used retaining wall types are a shown in Figures 5-10 through 5-12.

Figure 5-10

Gabion Baskets Gabion baskets are often used for both erosion protection and slope support. The baskets may be pre-formed or constructed on site. The baskets are usually made from twisted heavy steel wire mesh to create the desired size; these are then filled with rock. The tops of the baskets are wired closed. These baskets are then wired together end to end and/or stacked on each other.

Figure 5-11

Interlocking Block Walls Block walls are still one of the most common wall types, are easily constructed, and can be built to many configurations and for varied uses. This block wall is retaining the paved roadway behind it, as well as providing encasement for the drainpipe passing under the road and wall.

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Figure 5-12

Drilling for the Placement of a Soil Nail Wall Due to an unstable rocky soil formation in Oak Creek Canyon, Arizona, steel bars (soil nails) were grouted into drilled holes (35 to 45 ft into the slope), then a heavy steel mesh was connected to the exposed heads of the soil nails. The mesh was then sprayed with reddish color shotcrete for a more natural look, while also creating a retaining wall to protect the house pad from loose rock falling, or a possible shallow slope failure.

Chapter 5 Questions 1. Information in a geotechnical report often includes at least two of the following recommendations:

(a) (b) (c) (d)

The over-excavation of all sandy soils Preparation prior to fill placement Removal of unacceptable material Strict equipment type criteria

2. Expansive soils are often compacted at lower densities and higher moistures.

(a) (b)

True False

3. Pumping or deflection of clayey soil is acceptable in roadway subgrade.

(a) (b)

True False

4. The backscatter method of testing with a nuclear gauge should notbe used when testing a thin layer of aggregate base.

(a) (b)

True False

Chapter 5: Jobsite Soil Construction

5.

Which two conditions are desirable across a footing bottom?

(a) (b) (c) (d) 6.

Dense native soil Compacted fill contacting bedrock (cut/fill condition) CL/CH soil at under-optimum Compacted fill soil

A caisson was drilled to a depth of 60 ft, and upon completion water had seeped in and filled up 15 ft of the hole; what is the proper action to take prior to pouring concrete?

(a) (b) (c) (d)

Remeasure the hole, and then use a vac-truck to remove the water Confirm that the contractor will place a tremie to the bottom of the caisson during the pour. Pour low-slump concrete from the top of the caisson, making sure to vibrate from the bottom of the hole during the pour. Calculate the amount of concrete necessary to fill the caisson, with no adjustment made for the 15 ft of water.

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6 Geologic Considerations There are many cases of grading projects that have potentially hazardous geologic field conditions that go unnoticed and must be mitigated later. On the other hand, there are countless situations when a heads-up technician or inspector has recognized a hazardous field condition—notified the project engineer or geologist—and thereby saved the project from potential disaster and costly litigation. This is particularly true in hilly terrain, where bedrock is often close to the ground surface or unstable soil exists and a geologist is involved in the grading process. Certain geologic factors should be considered in hillside areas, in addition to the standard issues of grading in flat lands. The soil technician must be familiar with these geologic concerns. It is always a good idea for the technician to read the geotechnical report before the start of grading and discuss the project with the geologist. Special attention should be paid to the geologic map that indicates the location of surficial materials, such as alluvium, the different rock types that are anticipated, as well as review of the boring and trench logs. Be familiar with the regional geologic characteristics of the area that you are working within. Hillside grading projects—even for large residential developments—rarely have a full-time geologist on-site, often for budgetary reasons. Consequently, in hilly terrain where slopes are being cut, or buttresses are being built, a geologist should be requested to look at the cut-slope faces and keyway base and toe bottoms. Furthermore, the soil tech should always alert the project geologist when any unanticipated subsurface conditions are exposed.

Geologic Concerns on a Grading Project One of the most important responsibilities of the soil technician is to recognize potentially hazardous features that the project geologist is concerned with. A tech should alert the geologist immediately if field conditions require a closer geologic inspection. The ability to recognize possible geologic problems takes experience and careful attention to the soil and bedrock, both pre-exposed and those exposed during grading. The list on page 88 is of many features a geologist is concerned with on hillside grading projects that a soil technician should learn to recognize:

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Figure 6-1

Home Landslide This home in Laguna Beach, California, was totally destroyed by a bedrock landslide where an existing clay seam at the base of the slide was not initially recognized by the geologist.

Figure 6-2

Bitter Springs Landslide, Highway 89, Arizona This large portion of an ancient megaslide failed in a highway cut made in steep Triassic age sediments causing about 500 ft of roadway pavement to slip. Long-term erosion at the toe of the megaslide likely re-activated this landslide in part due to plastic deformation of the underlying Chinle Claystone Formation.

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Potentially unstable bedrock that may be exposed during benching. Exposed clay seams that could be related to faulting or landslides. Seeps or springs that may require drainage control. Heavy organics or uncontrolled fill that could destabilize the foundation material. Geologic units that require removal before placing fill: such as topsoil or heavy organics, slope-wash, alluvium, uncompacted or non-structural fill, landslide debris, or other unconsolidated materials. All such materials should be removed down to sound bedrock or stabilized by another means. It is up to the geotechnical technician to pay particular attention to these items, or any abrupt change in bedrock or soil conditions. For example, even an innocuous bedrock clay seam may—to a geologist—prove to be evidence of a large, past or imminent landslide. In some rare cases, especially in California or other western states, a clay seam or gouge between different rock types may indicate an active fault. Slope-wash and Alluvium are generally not difficult to recognize. They are commonly composed of relatively loose or unconsolidated mixtures of clay, silt, sand, and gravel. They may be deposited on a slope by actions of water and gravity, slow creep (slope wash), or deposited by a stream. These materials should be completely removed by excavating-placing a keyway if necessary, and benching before placing compacted fill, or addressed by other engineering means. Probably two of the most difficult features the soil technician may need to identify are daylighted bedding (also known as ‘out-of-slope bedding’), and uncontrolled fill. 1. Daylighted Bedding is simply sedimentary beds (strata) that are tilted downward, sloping towards the observer—out-of-slope—at an angle less than the slope face. A geologist measures the trend and slope of these beds using a small, hand-held geological compass (Brunton or similar) to help measure the ‘strike’ and ‘dip’ of a geologic feature. Being able to recognize potentially unstable daylighted bedding and to bring it to the geologist’s attention is extremely beneficial. 2. Uncontrolled Fill (artificial fill—AF) is sometimes extremely difficult to identify in the field, even by the experienced eye. It is almost always relatively loose, un-stratified, homogeneous (uniform texture), and may vary in color from the native soil nearby. One giveaway is scattered cultural artifacts, such as pieces of wire, glass, concrete, or other human debris. However, uncontrolled fill if placed with heavy equipment-but not observed or tested-can sometimes be dense, may vary in color and texture, and sometimes be non-homogeneous. The Brunton compass shown in Figure 6-3 is a geologist’s tool of the trade, and it is different from a regular compass—in that the East and West are flipped, so as to see it correctly on the mirror of the compass. It is mainly used for determining dip and strike; to find the inclination of slopes and rock formations.

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Figure 6-3

Brunton Compass At one time the mirror on this Brunton compass saved two lives, it was used to signal a rescue plane for a young geologist and his partner who were stranded in the Australian bush!

Recognition and Communication In summary, on hillside (or flat) grading projects, the technician or inspector should always be familiar with anticipated geologic conditions. The technician should also be able to recognize geologic features that may be significant to the geologist. Close communication with the geologist or geotechnical engineer, and a sharp eye for unexpected conditions will go a long way towards a successful grading project. If unsure, the technician should always have a geologist observe the site conditions.

Chapter 6 Questions 1.

Which of the following areas should a geologist be asked to inspect?

(a) (b) (c) (d) (e)

Keyway excavations Cut slopes Footing excavations in compacted fill A and C A and B

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2. It is not the technicians’ responsibility to be aware of geologic conditions.

(a) (b)

True False

3. Daylighted bedding may be observed as strata in a cut slope that dips into the slope face.

(a) (b)

True False

7 Geotechnical Bits and Pieces Technicians and Inspectors must be fully committed to each project in which they become involved. For a project to succeed, a symbiosis of both office and field personnel are necessary. Open communication and sharing of project information, ideas, and/or concerns is paramount. An inspector or technician in the field becomes the eyes and ears for the project manager, geologist, or engineer. Therefore, take many photos, keep a detailed daily diary, and communicate promptly—always attempt to be proactive— afterwards, it is often too late. Many similar testing and inspection standards are used in all regions. Conversely, due to regional climate, population density, financial, and other factors—not all standards may apply to every construction situation. Much of the material contained in this chapter ranges from typical recommendations and standards, to newer or sometimes unique methods of construction.

Compaction Equipment for General Grading Operations The type of equipment used for compaction greatly influences the ability to achieve adequate results. In fact, when the wrong equipment is used for specific soil conditions—acceptable compaction often cannot be obtained. For instance, using a small plate whacker for compacting a 6in. layer of aggregate base is not appropriate; nevertheless, contractors will often try to use a small plate whacker (vibra-plate) for compacting fill deeper than the machine is capable of managing. A geotechnical report often may not make recommendations about the type of compaction equipment to use. When specific equipment recommendations are not given in the report, do not direct the contractor regarding equipment type; just observe and document the contractor’s work. If recommendations are given in the geotechnical report as to the type of compaction equipment to be used (or not to be used!) for certain soil conditions, then it is the technician’s job to discuss the choice of equipment with the contractor. Should the contractor continue to use equipment not recommended, the technician should immediately inform the project engineer.

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Table 7-1 Compaction Equipment for General Grading Operations Soil or Material Type (Plasticity)

Compaction Equipment

Sandy and Gravelly (non-plastic) (SW, SP, SM, GW, GP, GM)

Most types of compaction equipment: Rubber-tired, Sheepsfoot (vibratory and non-vibe), Steel-drum vibe Roller

Sand-Clay-Silt blends, (low-med) (SC, SM, GC, GM, CL, ML)

Large Rubber-tired equipment, Heavy Sheepsfoot (non-vibe)

Clay and Silt mixes (med-high) (CL, CH, ML, MH, SC/CL)

Large Rubber-tired equipment, Heavy Sheepsfoot (non-vibe)

Aggregate Base for Roadways (NP) (GP, GM)

Large Steel-drum vibratory Roller, tight finishing with Large Vibra-plate *

Aggregate Base for sidewalk (NP) (GP, GM)

Small Steel-drum vibratory roller, Jumping jack, Med-large vibra plate *

Rock Fills: Generally untestable, with low to non-plastic ‘matrix’ material (Full-Time Observation)

Large/Heavy Compaction Equipment: Rubber-tired or Sheepsfoot (vibe or non); Continually mixed/track walked by large Dozer (D-9 equiv. or larger)

* A small vibra-plate should not be used for compacting lifts thicker than 3 in.

Table 7-2 Compaction for Equipment for Trench or Wall Backfill Soil or Material Type (Plasticity)

Compaction Equipment

Sandy and Gravelly (non-plastic) (SW, SP, SM, GW, GP, GM) (including Aggregate Base)

Excavator or Backhoe with Compaction Wheel, Jumping Jack, Remote Controlled vibe Sheepsfoot Roller, Med-large vibra plate *

Sand-Clay-Silt blends, (low-med) (SC, SM, GC, GM, CL, ML)

Excavator or Backhoe with Compaction Wheel, Jumping Jack, R-C vibe Sheepsfoot Roller, Med-large vibra plate.*

Clay and Silt mixes (med-high) (CL, CH, ML, MH, SC/CL)

Excavator or Backhoe with Compaction Wheel, or a Jumping Jack

Pea Gravel or Crushed Rock

Vibrated or Impacted to settle materials

*A small vibra-plate should not be used for compacting lifts thicker than 3 in. All trenches must be made safe per OSHA 29, Subpart P—Excavations

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Remember, if the wrong compaction methods are used, a failing density test emphasizes the need for a change in compaction equipment or method. Tables 7-1 and 7-2 indicate which types of compaction equipment are generally best for each soil or material condition.

Figure 7-1

Creative Backfill Operation Due to the infra-structure at the Sacramento International Airport and how it was sequenced, the on-site and/or imported material had to be creatively moved to the wall fill area—by a combination of trucking, conveyor belt, and large PVC tube. The soil (an SC/SM) was compacted using a vibratory sheepsfoot roller, with two jumping jacks for support along the wall. Lift thickness lines were painted on the wall, so the equipment operators, laborers, foreman, and the soil tech could easily follow, coordinate, and test the compaction operation.

Figure 7-2

Hard to Reach Backfill Area Excavators with compaction wheels are great for compacting hard to reach areas!

Chapter 7: Geotechnical Bits and Pieces

Green Grading for Low Impact Development (LID) Under the United States Environmental Protection Agency (EPA), the Clean Water Act (CWA) requires the control of stormwater runoff. The National Pollution Discharge Elimination System (NPDES) is authorized to enforce aspects of the CWA, and issue permits to help manage stormwater discharge through the use of Best Management Practices (BMPs). These BMPs are required to treat and mitigate stormwater runoff caused by urban development. During urban development, much of previously undisturbed ground becomes built over with parking areas, as well as private and commercial structures. The LID systems help to offset the occluded absorption areas caused during grading and construction. LID systems such as Infiltration Trenches and Vegetated Bioswales shown by photos in Figure 7-3 are one example of the “Treatment BMPs” placed during the grading of new developments. These features help to add controlled infiltration into the ground, thus helping to replenish the natural aquifer and nearby soils. At the same time, LID systems prevent and minimize the runoff of sediments and pollutants into nearby natural resources, such as: into storm drains, creeks, streams, rivers, lakes, and oceans. LID systems often include underground stormwater capture, storage, and infiltration systems. Even pervious concrete and special pervious “structural

Figure 7-3

This bioswale is sized to meet the specific volume calculated to satisfy post construction stormwater controls. During excavation and placement of these bioswales—the length, width, and depth are mandatory inspection considerations. Each must meet the “SWLID” (Stormwater Low Impact Development) project plan specifications.

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soil” is commonly used. Inspection and testing of these BMPs is performed during various phases of site grading. Beneath the freshly vegetated rock swales shown in Figure 7-3 a specified depth of biosoil, encased with 10 ml visqueen on the swale wall sides, but open across the bottom to allow for infiltration. The type of biosoil media, as determined by the engineer, must provide required contact time, non-ponding time, and other criteria. The grated drain is a “high flow bypass” connected to the municipal storm drain system. Only during excessive rain events when water runoff exceeds the swale capture capacity, will water flow into the “high flow” grated inlet.

Geotechnical Construction Integrated with Green Power As the earth’s resources, climate, and environment continue to change—the construction industry must adapt. Geotechnical recommendations, implementation, and materials used will also continue to progress. For instance: wind power, geothermal power, and solar power each have many geotechnical designs interwoven within the specifics of these projects. It is common that technicians and inspectors are involved in such construction. Examples include: v Wind Turbines: simple spread footings are not sufficient enough to support tall wind turbines. The type of foundation necessary is influenced by a variety of factors, such as: subsurface soil (or rock) conditions, tower height, wind loads, seismic loads and more. Much of this engineering occurs below the ground (geotechnical), and may include large precast foundations supported on re-compacted or specially densified soils, deep steel reinforced concrete piers, and other unique soil/structural combinations. v Geothermal Energy, (shallow): geothermal heat pumps and systems are commonly utilized for individual home and commercial structures to obtain heating using clean energy, by transferring heat from “shallow based” geothermal lines and coils. The heating (or cooling) systems function is based on the earth’s capability to store heat in shallow ground formations. Liquid passes from pipes exiting the home or other structures into the ground (often 6 to 10 ft in depth) and circulates in pipes and coils to gain the ambient ground temperature and is then circulated back into the structure to help maintain comfortable environment. The geology of the soil strata in the transfer zone is crucial since heat transfer varies between soil types or rock formations. A geotechnical investigation helps to determine the best depth for placement of the geothermal lines and coils. v Geothermal Power Plant Energy: there are different types of geothermal power plants. However, each uses steam to run turbines, typically by injecting water (or another fluid) deep enough to reach the heated formation being warmed by the magma further below. The Geysers geothermal field located in Northern California is currently the

Chapter 7: Geotechnical Bits and Pieces

largest complex of geothermal power plants in the world. The Geysers complex of plants has a rated capacity of approximately 1.59 GW and produces near 800 megawatts of power. Energy from the Geysers supply electricity throughout most of the region of Northern California—north of the Golden Gate Bridge. To replenish the steam necessary to run power plants, the Calpine Corporation partnered with Santa Rosa City to build 41 miles of 12 in. pipeline, establishing the Santa Rosa Geyser Recharge Project. The SRGRP enables millions of gallons of highly treated waste water (tertiary reclaimed water) to be pumped to the geothermal plants. This tertiary waste water is injected into the ground to create steam which operates the turbine generators. In addition, the Town of Windsor has teamed with Santa Rosa City and pumps reclaimed water from their recently solar powered waste water treatment plant (WWTP) into the SRGRP pipeline. This pipeline is monitored and inspected to mitigate damage from natural elements including landslides, seismic, and flooding. Geotechnical investigation and design are required as part of the mitigation process. v Anchored Floating Solar Array: to reduce power costs of a waste water treatment plant in Windsor, California, floating solar panels were installed. A total of 4,959 panels were hooked together in a floating array on a large reclaimed water pond. Each panel (3'3" × 6'5" × 1½") supplies 360 watts, giving a total power output of 1.785 MW (Figure 7-4). On sunny days, the solar panels supply power to the WWTP—with any excess power fed into the electric grid; while on days that are too cloudy, the power is retrieved back from the local grid (finished view photos, Figure 7-5). The floating array covers approximately 1/3 of the pond. To keep it stable in windy conditions, it had to be anchored from all sides. The array is held firmly by “Platipus” brand anchors (B-6 and B-8 sizes). Each anchor was driven into place by a small excavator with a hydraulic hammer type attachment (Figure 7-6). After an anchor was driven to depth (typically 12 to 15 ft), it would then be pulled back to “lock” into place. A “pull test” was performed on each anchor to

Figure 7-4

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Figure 7-5

Figure 7-6

Chapter 7: Geotechnical Bits and Pieces

verify that the anchors were set properly. The project geotechnical engineer recommended the depth and pull test strength (typically 10,000 12,000 lb) depending on the placement location and the soil formation.

Lime Treating Treating overly wet soil with lime for stabilization is commonly used in many regions. Lime treating may be used in stabilization—of soft, wet, and pumping road subgrade—or simply to dry back wet soil prior to placement as trench backfill. High calcium ‘quicklime’ (CaO) or high calcium ‘hydrated lime’ (Ca OH2) are often used, typically in powdered form. These limes range from a PH of ~11.5 to 12.5 (strongly alkaline). There are other lime mixtures that include dolomitic lime, and lime can even be blended with dry cement for stabilization usage. When using lime for stabilization, there are three general phases during the process: an initial mixing, followed by a curing time (sometimes referred to as ‘mellowing time’), and then a final re-mixing and compaction phase. Timing, planning, and quality control are vital when lime treating for stabilization. Following are some basic, yet important guidelines: •

•

• • •

•

The significance of a proper mix design cannot be understated. The percent of lime to the dry weight of the soil is based on many factors. The soil type is integral on the pozzolanic reaction, which occurs best with a higher percentage of clay (CL or CH) in the soil to be treated. Also, certain types of clay have a stronger pozzolanic reaction. Mixing depth can never be deeper than the compaction equipment can handle; too deep a mix followed by too light of compaction equipment may leave a layer of under-consolidated lime treated soil at the lower portion of the mixed zone. Compaction equipment usually consists of a large sheepsfoot compactor (equivalent to a Cat 815, or larger), with a heavy steel drum roller to finish. After initial placement and mixing of the lime into the soil, the area should cure (or “mellow”), for a minimum of 24 hours, and sometimes longer if recommended by the geotechnical engineer. During the initial mixing process, it is important to determine if the lime is being thoroughly blended. Using a plastic spray bottle with phenolphthalein, the surface may be sprayed in various locations. Phenolphthalein will turn pink in the presence of a base (alkaline), and since lime is a strong base, the area sprayed should be a consistent pink, indicating a good mixture. In Figure 7-7 only a dropper was used to test a lime/concrete mix being used for subgrade stabilization in an SC/SM soil. After the final compaction, and the curing process is complete, dry density tests can be taken. Road subgrade density is usually 95% of the laboratory modified Proctor (ASTM D 1557), or as recommended. However, it is important for the contractor and the technician to obtain prompt test results;

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Figure 7-7

Phenolphthalein is a known irritant, wear gloves and use safely.

Figure 7-8

This high calcium lime mix was placed to stabilize a levee road subgrade. During dry lime treatment, it is important to monitor the wind; placement with wind greater than 20mph should be avoided. Lime is caustic and should not be inhaled or touched.

and because the mix is constantly hydrating—causing the moisture to change and the mix to become less workable—using a nuclear gauge to take wet density readings can help remove moisture variables from the results. Comparing the lab maximum wet density with the gauge wet density is one method used. To avoid touching the lime mix, do not use a sand cone test.

Chapter 7: Geotechnical Bits and Pieces

Figure 7-9

Due to recent rains, and the developer’s need to access the inside portion of the site, the interior loop road subgrade soil was treated with a mixture of cement and lime. The addition of cement worked well for this condition, since the subgrade soils varied, ranging from SM to CL.

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8 Project Management and Preparation The job a technician or inspector performs in the field is especially valuable. They are the eyes of the project engineer or geologist—observing and documenting the work performed by the grading contractor on the project. Techs and inspectors must keep written records (such as a daily diary) of their observations, manage time between various projects, and maintain regular contact with the construction team; the project engineer, contractor, and other involved personnel. The range of work a technician performs during projects can be divided into multiple phases: Project Preparation, Observation, Communication, Testing, and the Documentation of data for the final report.

Project Preparation Before beginning actual field work on a new project, technicians must become familiar with the grading contractor’s scope of work; this will help in preparing for the testing and inspection they must perform during the course of the project. A discussion with the project manager (engineer, geologist, or supervisor) is a good place to start. Important factors to consider are the project duration, if the job is to be full or part time, and the estimated budget. The planned budget may include such items as a calculation of the number and type of tests to be performed (both field and lab), hours of field time and number of field personnel, as well as any special field equipment necessary to complete the job. A technician must review the geotechnical report and familiarize themselves with the boring or trench logs to better understand the various site soil conditions, including their locations and depths. When reviewing the structural plans, note the location and types of proposed structures, paying attention to foundation types, footing depths, and steel and concrete specifications. One of the most important preparations a technician can make during reviewing the geotechnical report is to highlight important portions of the recommendations. Key points to highlight include the following:

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Soils that may require special handling, such as: expansive clays, porous silts, diatomaceous, gypsiferous, organic, and any other site-specific soils Degree of compaction required, since compaction recommendations often vary depending on soil type or usage (deeper fill, subgrade, aggregate base, expansive soil, etc.) Moisture requirements, which may also vary with the different site soils Project-specific construction, such as: Keyways, buttress fills, slide removals, and subdrain placements Before most jobs start, a “pre-grade” (or pre-con) meeting must be held. Representatives from the developer, grading contractor, civil engineer or architect, soils engineer, inspector, and lead technician should attend. This is an excellent opportunity to discuss job-related concerns. Don’t assume that everybody is on the same page; the more thorough the pre-grade meeting is, the less likely any surprises during the project will occur. The pre-grade meeting is also a time to remind the contractor of any unusual or special recommendations and specifications, such as discussing the project geotechnical recommendations. Important points of discussion at the pre-grade meeting may include the following: The contractor’s “plan of attack”; type of grading equipment, order of areas to be graded, time frame to complete grading, and other contractor goals Grading Plan review; a full-sized paper set is often best for this initial review Storm Water and LID features, including BMP’s, SWPPP, and MS4 criteria Review job safety requirements: For example, make certain that nearby equipment is to be stopped while you are taking a density test and that no work or testing shall be allowed inside an unsafe trench. Find out who the ‘Competent Person’ is (per OSHA Standard 1926.32 f). A dialogue with the contractor (especially the site foreman) about the recommendations presented in the geotechnical report, such as: compaction and moisture requirements, benching and keying details, over-excavation or removals, and other special grading requirements. Tip: Although contractors are supposed to bid for a job based on the project recommendations, they can misunderstand an important recommendation or may not fully understand site soil conditions. Hence, it always helps to review the report and plans with them, thereby avoiding errors resulting from miscommunication and/or misconceptions.

Observation Being in the right place at the right time—the ability to foresee the contractor’s next move—is a valuable skill for a technician or inspector. For instance, if a contractor is placing fill at one end of a project and making a removal at the other end, you must decide where you should spend the most time—or whether

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Figure 8-1

Trench Safety In the first photo, a worker can be seen in an un-shored trench that was nearly 6ft. deep. Both ends of the trench passed under the curb and gutter. Upon noticing, the unsafe condition, the inspector immediately informed the site superintendent. The super quickly ordered the workers out of the trench. Photo B was taken across the road about a half hour later; the shoring had been placed safely throughout the trench length. A simple ½ hour—more or less—can protect lives!

to divide your time equally between the two areas. Often the best approach is to spend the majority of your time observing the fill placement, and only stopping by the removal area when scheduled. Reach an agreement with the contractor that you must be requested to observe the bottom of the excavation—only when the contractor believes the removal is complete—and that no fill will be placed prior to your approval of the bottom. Keep in mind that a contractor is usually more willing to add a little more effort during fill placement, rather than to remove and rework an already placed fill. Therefore, if during fill placement you notice an area of concern (e.g., poorly mixed soil, nesting of oversized material, or too much moisture), you should alert the foreman of these concerns immediately, and not wait until the point at which fill must be removed to correct the problem. By taking this approach you can save the contractor (and yourself) a lot of time and effort (and sometimes heated discussion). Plan ahead try to foresee problems-be proactive. While observing the grading process, ask yourself the following questions: v Does the fill have sufficient mixing and moisture conditioning? v Is there proper benching around the outer edges of fills to tie into existing dense native soil, rock, or engineered fill? v Is there adequate overbuild or compaction of fill slope faces? (Remind the contractor that an under-built slope is unacceptable; pasting soil onto a slope face after the slope has been built is not structurally sound).

Chapter 8: Project Management and Preparation

v Have removals (e.g., canyon, alluvial soils, old fills, and stockpiles) been benched, removed, or handled properly? v Were all excavations for transition lots, porous soils, non-engineered fill, old foundations, trees, bottom cleanouts and stockpile removals observed? It is also important to observe other areas of particular concern. These include: cut slopes (check for out-of-slope bedding, slide planes, seeps, or loose material), non-engineered fill (watch for buried debris, tanks, or old foundations), porous, and soft soils. The Project Data Sheet shown in Figure 8-2 is a handy reference for a grading project.

Communication Upon noticing an area of concern, good communication skills are paramount. The quicker a technician can bring a concern to the attention of the contractor, project manager, or supervisor—the sooner a corrective action can be addressed. The importance of tact cannot be understated; try not to put the contractor on the defensive or to ‘point fingers’ when discussing an issue, but at the same time be firm. While helping to correct a complication, do not direct the contractor on how to perform the work. Should your method be ineffective, the contractor may blame you for any wasted time and material! This does not mean that you should not offer alternative suggestions—just make it clear to the contractor that the decision on how they perform the work is entirely up to them. Technicians should be concerned with the final product, typically not the process. There can be exceptions to directing the procedure that a contractor should undertake, but those directives usually come from an engineer or geologist. There are occasions when due to time constraints (caused by weather, project schedule, etc.) that a field drawing is efficient (such as Figure 8-3) and may help to better communicate a prior verbally agreed upon plan. Before sharing your drawing with the contractor, take a picture or scan of it; then text or email it to your project manager for their approval.

Testing Sample materials prior to placement—then when testing during placement, results can be calculated. Sampling and testing help to determine whether the geotechnical recommendations (plans or specifications) are being followed during grading and construction. Nuclear gauges, and less often sand cones, are used to test the density and moisture content during fill placement. Safety while testing is of the utmost importance. Always coordinate your testing with the foreman and/or the equipment operators. Nearby equipment should be shut down and your presence should be made obvious. Eye contact with equipment operators is

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Figure 8-2

Project Data Sheet

Chapter 8: Project Management and Preparation

Figure 8-3

Field Sketch

essential, the operator must see and acknowledge your presence before you enter the swing zone of an excavator. Never attempt to walk behind moving equipment. Tip: When possible, schedule your test taking for a time when equipment is not operating. For example: before operators start up, while they are breaking for lunch, and after they shut down for the day, are all good options. When planned right, contractors can minimize disrupting their grading operations for your testing. However, there are often times that fill lifts are being placed quickly and a contractor must stop to allow density tests to be taken. If you must take a density test where scrapers, dozers, or other heavy equipment are working nearby, the following tips are valuable (and often mandatory) safety guidelines: v Always wear a bright colored (retro-reflective) safety vest and a hardhat. v Make sure the foreman and operators are aware that you are taking tests, and that you are fully visible and are safely protected from construction. v When taking a density test in an active scraper fill area, park your vehicle in front of the open end of the excavation. Place cross laths with a bright surveyor’s ribbon tied to them on top of the spoil pile at the end of the excavation. v Carefully watch and listen for equipment and check haul road directions. Notify the contractor of a failing density test result as soon as possible. When a density test has failed, record the test location and elevation on your plans and test sheet. If necessary, leave a lath where the failing test was taken to help warn operators not to bury the test hole until the foreman has a chance to observe the fill. With the foreman present it is easier to point out dry, poorly mixed, or loose areas. Use your probe to find and emphasize loose areas. It is critical that the technician and the foreman reach an agreement on the limits of an area that is to be reworked. Sometimes more testing will be needed to

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better define the limits of unacceptable fill, but often it is a simple matter of recompacting the last lift of material placed. Usually, simply returning to retest the area after it has been reworked is adequate. However, if the limits of the area are hard to define in advance, the technician should stay to observe the contractor’s operation during their rework. In all cases—upon completion of rework—density retests must be taken at approximately the same location and elevation of the initial test failure(s). Proper documentation of the retest is necessary to show that the failed area has been adequately reworked. For example, if the original test failure number was 43, then the retest number should incorporate the original failure number, such as 43R.

Documentation All of the technician’s observations, conversations, and test data must be documented. Technicians must write a separate Daily Field Report (DFR) for each project worked on, daily (Figure 8-4). The DFR is important documentation, it is the written record of meetings, discussions, issues of concern, locations of removals and fills, equipment utilized, and any other important developments that transpire on the job during the day. Technicians should have their own personal daily diary or electronic notebook (size and style of their choice) in which they record a general overview (and often very specific conversations) of discussions and activities at each project they visit. This personal daily diary is kept for the technician’s own reference and is a valuable documentation. It can include contact names, phone numbers, time on the jobs, and often crucial evidence of conversations at—and related to —each project worked on. Every test taken throughout the day should be plotted, either on the grading plans or on a hand-drawn plot plan. The location of each sample (maximum density, expansion, R value, etc.) obtained from the site should also be plotted and defined on the sample tag. Density test information should be recorded numerically; beginning with test #1 on the first day a test was taken and continuing numerically— not restarting from #1 again each day—on a density test sheet or a density test summary form (see Figures 8-4 and 8-5). Note: The compilation of data for the final grading report is continued throughout the length of the project. If testing and other documentation is kept current on a daily basis, paperwork can easily be compiled when the project ends; subsequently making the writing of the final report a relatively simple process.

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Figure 8-4

Daily Field Report (DFR)

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Figure 8-5

Density Test Summary Sheet

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A Technician’s Steps to Success These guidelines can earn respect, maintain ethics, and enhance effectiveness on the job. Be safe: never sacrifice job safety for job expediency. Prepare: one way to gain the respect of the contractor and your associates is to thoroughly understand the project plans and reports. Communicate clearly with the project engineer or geologist. Be organized: have plans and other job information (paper or electronic) handy. Walk the project: read the grade stakes or other markings. Study the site, visualize how the contractor might grade the site, and note areas of concern. Be proactive: obtain Proctor and other necessary samples in advance whenever possible. Attend a pre-job meeting (preferably on site) and take detailed notes. Be Consistent-make your decisions based on the plans and specifications. Be equipped: have the necessary safety, test equipment, and supplies on hand. Build trust through integrity, honesty, and good ethics. I must keep on learning...to make up for what I’ve forgotten.

Chapter 8 Questions 1.

While reviewing a geotechnical report in preparation for a new project, which item would be least important to the geotechnical technician?

(a) (b) (c) (d) 2.

At the pre-grade meeting, safety should not be discussed by the technician.

(a) (b) 3.

True False

A vibra-plate is best for compacting lifts of clay.

(a) (b) 4.

Whether old fill or foundations exist on site Recommendations for the degree of compaction The height of the structure(s) (three, four stories, etc.) Whether there are transition (cut/fill) lots

True False

If a certain type of compaction equipment is not working well, it is permissible to suggest other options to the contractor.

(a) (b)

True False

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5. Which of the two following grading processes are important for the geotechnical technician to observe?

(a) (b) (c) (d)

The proper maintenance of the compaction equipment Benching into slopes during fill placement Depth of removals and over-excavations Placement of a benchmark by the surveyors

6. The wearing of a safety vest is necessary only during roadway projects.

(a) (b)

True False

7. Density tests should never be taken before or after a contractor begins or stops work for the day.

(a) (b)

True False

9 Putting It All Together: An Example Project Scenario A geotechnical firm is asked by a local developer to perform a geotechnical investigation on a nearby 14-acre plot of land. The developer states that he tentatively wants to build an approximately 280-unit apartment complex and associated roadways and parking areas. The site is currently vacant with no existing structures and is fronted along the south by a two-lane paved road. Information obtained from the site investigation will be used by the project engineer to develop recommendations for earthwork and specifications for foundations, paved parking areas and driveways, concrete flatwork, and utility placement. During exploration, lab work, subsequent grading and construction, technicians from the firm will often be involved. Prior to beginning a project, a technician's preparation is paramount. Many important tasks should be addressed: site investigation, office pre-job meetings, project organization, and attending an on-site pre-grade meeting. Refer to Chapter 8 for a comprehensive discussion of field responsibilities during a grading project. An example geotechnical report is presented at the end of this chapter.

Site Investigation Before beginning field work for a site investigation, a project engineer has much preparation to do: determining the scope of the work, estimating a budget for engineering services, getting a signed contract with the developer, applying for permits, hiring a drilling rig (or backhoe) crew, determining the type of exploration needed (e.g., boreholes, trenches, and rippability study), and performing many other coordination tasks.

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Initial Site Visit A technician may be asked to do a site reconnaissance during the planning process. Some of the site information necessary to gather for the project engineer will include the following: Locating all existing underground utilities within the area of investigation. This is the most important item of concern; before doing any underground work, a utility-locating organization (such as Underground Service Alert or another regional agency) must be contacted. Ascertaining site accessibility. Is the site fenced or does it have a locked gate? Are some areas impassible without four-wheel-drive or track-mounted equipment because of soft or steep terrain? Potential hazards to avoid during site exploration—including overhead power, or underground structures. Creating a site sketch that includes information such as approximate locations of any existing structures, septic tanks, stockpiles, large trees (or planted areas—orchards, farmed fields, etc.), dirt or paved roads, and any other natural or artificial features. Once a date for the site exploration has been set, and the locations of boreholes and trenches have been tentatively laid out, it is wise to pre-locate them with numbered survey stakes (B-1, T-2) prior to the time the drill rig or backhoe arrives on-site, thus saving valuable equipment and operator time. Boreholes and trenches should be numbered sequentially, in the order explored. Determine the best access to each staked location and discuss the type of testing necessary and the terrain to be traversed with the drill-rig and/or backhoe operators.

Borehole and Trench Logging Have all supplies necessary for sampling and logging ready the day before the investigation. Useful supplies necessary for field investigations include: Large and small plastic sample bags Sample tags and labels Boring and trench logs Sampling equipment: split barrel sampler (SPT and ring sampler), plastic ring sample jars, and sample tubes Sampling supply box with a variety of supplies, including electrical tape, duct tape, indelible markers, sample cutting blades or saw with piano wire, water squirt bottle, soil color chart, large pipe wrenches, flat-head screwdrivers, large and small wire brushes, and any other helpful items Miscellaneous supplies such as a geologist hammer, magnifying lens, a flat-head shovel, plywood board for cutting apart samples on, boxes with foam-padded inserts for shipping ring/tube samples, rags, paper towels,

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gloves, and a chain vise (which can be effective for breaking sample barrels loose) During exploration in the field, plot each borehole or trench location on a site plan. Take the necessary time to either measure or GPS the location of each boring and trench for ease and accurate transfer to the final report plot plan. A topographic site plan with borehole and trench locations is shown within the Example Geotechnical Report on Figure 2. After the sampling is done, in order to protect the samples during shipment to the lab, they should be placed in well-padded containers and transported carefully in the ‘upward’ position. An outline of exploration and sampling methods, including sample transportation, is described more thoroughly in Chapter 2 of this book.

Laboratory Testing When the samples are received by the lab, the project engineer will determine which samples to test and the specific tests to be run on each specimen. Test requests for the project will be submitted to the lab manager, who will then prepare a testing program. Each test will be performed by a technician experienced in performing the specific test procedure according to the necessary standard (ASTM, AASHTO, etc.). The test results will then be reviewed by the lab manager and the project engineer. Upon completion of both the field exploration and the laboratory analysis, the information will be used by the engineer as a guide in creating recommendations and designing criteria which will be set forth in the geotechnical report.

Office Pre-job Meeting Once a starting date has been scheduled for a project, an office meeting should be held. Both the technician who will be on the job and the engineer who will be the project manager should attend the meeting. Note: This meeting with the project engineer is the best way to plan and get information about the project—don't hesitate to ask questions, and get clarifications. During the meeting, the technician should learn as much information as possible about the project, including: The agreed upon starting date and an estimated length of time for the job. A full discussion of the geotechnical report, including: • Anticipated soil, rock, or other materials to be encountered, and treatment of these materials during grading, such as moisture and density criteria • Removals: old structures, trees, stockpiles, and organic material • Over-excavation and re-compaction of porous, soft, or expansive soils, and cut/fill pads areas

Chapter 9: Putting It All Together: An Example Project

•

Special grading, such as buttress fills, slide removals, canyon cleanouts, rock fills, and LID features. • Foundation recommendations Contractor and client relations and roles should be established. The preferred method for relaying field and lab test results should be clarified (e.g., initially verbal—followed by paper or electronic communication) Budget is important; will the project be full or part-time? How many hours per day are required? What type of lab and field testing will be necessary?

Project Organization This point cannot be emphasized enough, it is important to prepare in advance, being proactive will make a job run smoother. The following are some useful tips:

Example Geotechnical Report 1.

2. 3. 4.

5.

Create a Field File, (electronic and/or paper). This should include: ✓ Project Data Sheet (similar to Figure 8.2) ✓ Daily Field Reports (Figure 8-4) ✓ Density Test Summary (Figure 8-5) ✓ Lab Data, including numbered Proctors (each with a complete soil description), and all other lab data added during the project ✓ Correspondence—from your office, the contractor, the developer; including updated plans and details Review the Plans, including structure type and location, utility type and location, stormwater and LID features (SWLID plan). Drive/walk the Jobsite. This is the best way to become familiar with the site, and to observe conditions that may not have been noticed before. Pick up Proctor native samples in advance whenever possible, and obtain import samples when the supplier is known (many projects have this information in “submittals.” Attend an on-site Pre-con Meeting (pre-grade meeting); this is a great time to get the contractor’s viewpoint of the project, review the plans together, and for all parties involved to discuss any other questions or concerns.

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Project No. 2018.42.G GEOTECHNICAL REPORT For the PROPOSED 280 UNIT APARTMENT COMPLEX, ‘PARCEL 36C’ Located in WOODVILLE HEIGHTS, WOODVILLE, CALIFORNIA Prepared for: Mr. Ron Adams, Woodville Realtors Association 3500 N. Main Street Woodville, California 98392 Dear Mr. Adams, The Geotechnical Testing and Observation Group (GTOG) is pleased to present the results of this geotechnical site evaluation for the proposed 280 unit apartment complex to be built on Parcel 36C in the city of Woodville, California. Our report presents a geotechnical evaluation of the site along with conclusions and recommendations for the design and construction of the proposed project. GTOG appreciates the opportunity to be of service to you during this phase of your project. Sincerely, GTOG John L. Rosen, P.E. Project Engineer

Jeffery K. Fitzpatrick, G.E. Sr. Geotechnical Engineer

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PARCEL 36C Table of Contents 1.

2.

3.

4.

5.

6.

Introduction 1.1 Scope of Services 1.2 Project Location and Description Findings 2.1 Investigation and Site Conditions 2.1.1 Site Geology 2.1.2 Surface Conditions 2.1.3 Surface Conditions 2.1.4 Groundwater 2.2 Laboratory Testing Conclusions 3.1 Excavatability 3.1.1 General Removals 3.1.2 Trench Excavations 3.2 Excavatability Earthwork Recommendations 4.1 Clearing and Grubbing 4.1.1 Subgrade Preparation 4.2 Clearing and Grubbing 4.2.1 Native Material 4.2.2 Import Material 4.3 Engineered Fill Placement 4.3.1 Fill Slopes 4.3.1.1 Density Test Frequency 4.3.2 Rock Fill 4.3.3 Cut/Fill (Transition) Building Pads 4.3.4 Pavement Areas 4.3.5 Exterior Concrete Flatwork 4.3.6 Exterior Concrete Flatwork 4.4 Unstable Subgrade Mitigation Options 4.5 Slopes 4.5.1 Cut Slopes 4.5.2 Fill Slopes 4.6 Surface Drainage Earthwork Recommendations 5.1 Footings 5.1.1 Dimensions and Bearing Capacity 5.1.2 Lateral Resistance 5.1.3 Settlement 5.2 Slabs on Grade 5.3 Exterior Concrete Flatwork Pavement Design 6.1 Flexible Pavement (Asphaltic Concrete) 6.2 Rigid Pavements (Reinforced Concrete)

Project No. 2018.42.G

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Figures

Figure 1 Site Vicinity Map Figure 2 Site Plan with Trench and Boring Locations Appendixes

Appendix A Trench Logs Appendix B Boring Logs Appendix C Laboratory Test Results

1. Introduction In accordance with authorization by Woodville Realtors Association the Geotechnical Testing and Observation Group (GTOG) has completed a Geotechnical Report for the proposed 280 unit apartment complex to be located on an approximately 14 acre parcel (Parcel 36C) in Woodville, California.

1.1 Scope of Services We performed our services consistent with the scope of work presented in our Proposal No. 2016.84.P dated May 18, 2016. The scope of services for this project included: A review of existing engineering and geologic data relative to the project site Field exploration Soil and laboratory testing Data analysis and conclusions Report preparation

1.2 Project Location and Description The project is located along the north side of Albert Drive, approximately 0.25 miles west of Lincoln Parkway in the city of Woodville, California, as shown on Figure 1. The site is approximately 14 acres and is surrounded by private property to the east and west and abutting most of the north perimeter is US Forest Service land. A natural drainage course passes roughly east/west outside the northern property boundary, in which slow running water was observed during our initial site exploration. Undeveloped fields lay along both the east and west property boundaries.

2. Findings 2.1 Investigation and Site Conditions This section presents site conditions—including geologic setting, surface conditions, general soil/rock, and groundwater conditions—and laboratory test results.

Chapter 9: Putting It All Together: An Example Project

2.1.1 Site Geology The USGS Geologic Map of the Late Cenozoic Deposits of the Sacramento Valley and the Northern Sierra Foothills, California (by E. J. Helley and D. S. Harwood, 1985) was referred to for descriptions of mapped geologic units at the site. The site is primarily underlain by sedimentary deposits of the Mehrten Formation, which were deposited during the Upper Miocene to the Lower Pliocene geologic time epochs, approximately 3 to 5 million years ago. The Mehrten Formation consists of both breccia and conglomerate. Breccia: This unit is made up of a series of pyroclastic mudflows that consist of angular andesite cobbles and boulders, surrounded by tuffaceous siltstone. The pyroclastic mudflow unit forms erosion-resistant caps over the softer, more easily eroded conglomerate unit. Unconfined compressive strengths in the breccia commonly range from 1,500 to 2,500 psi. Conglomerate: The conglomerate contains rounded to subrounded cobbles in a siltstone/ sandstone matrix. Separate beds of siltstone and sandstone are often found in the conglomerate. Mehrten conglomerate typically consists of approximately ⅔ gravel, cobbles, and boulders and about ⅓ matrix soil—which is silty Sand and sandy Silt (SM and ML). During our exploration, we observed conglomerate exposed at the surface in most of the central and northern portions of the site, with outcroppings of breccia in the southern area of the site. 2.1.2 Surface Conditions Figure 9-2 shows the approximate site topography prior to the construction of Albert Drive. Elevation contours shown on Figure 9-2 were surveyed by Johns and Brown Engineering in 1999 and are intended for preliminary design purposes only. Based on this topographic information, the site generally slopes downhill in a northerly direction and has a low elevation in the northwest of approximately 158 ft to a high in the southeast site of 198 ft (mean Sea Level). At the time of our investigation the site was sparsely vegetated with low annual grasses and a few tall weeds. No existing structures were present. Several surface boulders ranging from 1 to 4 ft in dimension were observed. No stockpiles or other surface debris were noted. 2.1.3 Subsurface Conditions GTOG logged three trenches and five air rotary borings. No fill was encountered during our exploration. In general, the results of our borings and trenches indicate that the central and northern portions of the site are blanketed by a soft, near-saturated sandy Silt (ML) layer from 6 to 18 in. thick. This sandy Silt layer is underlain by both conglomerate and breccia, except where conglomerate and breccia is exposed at the surface, generally in the northern portion of the site. During our investigation, we did not encounter expansive, noticeably porous, or compressible soils.

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2.1.4 Groundwater We did not encounter groundwater in our trench excavations or borings. The State of California Department of Water Resources static ground water maps show static groundwater at an approximate elevation of 60 ft. This elevation is approximately 100 ft below the site surface.

2.2 Laboratory Testing Minimal testing was performed in Mehrten conglomerate and breccia because of the difficulty in sampling and testing these formations. However, plasticity, gradation, R-value, and maximum density tests were performed in the relatively thin upper soil formation of sandy Silt in the northern site area. Laboratory test results are presented in Appendix C.

3. Conclusions In our opinion, from a geotechnical viewpoint, the planned development may be constructed as discussed, provided the design is performed in accordance with recommendations presented in this report. A primary geotechnical concern at the site is the excavatability of the native breccia and conglomerate formations. Below we present a brief discussion of this issue, including seismic parameters, followed by our detailed recommendations for construction of the project.

3.1 Excavatability The relatively thin layer of sandy Silt in the central and northern portions of the site should be easy to remove with conventional grading equipment. Excavation of the conglomerate and breccia will take more effort, as described below. 3.1.1 General Removals The existing native conglomerate should be excavatable with conventional large grading equipment such as a CAT D9 bulldozer and a CAT 245 excavator. However, native breccia may require single shank ripping with a CAT D10 bulldozer (or equivalent). In the southern portion of the site, breccia was encountered at the surface down to a depth of 5 ft in both trench T-1 and boring B-2, and breccia was exposed in trench T-2 from 1 to 11 ft deep. 3.1.2 Trench Excavations Trenching in conglomerate or breccia may require large excavators or rock trenchers.

3.2 Seismic Parameters Due to the low groundwater table, approximately 100 ft below the existing surface, and a large percentage of gravel and cobbles, we do not expect liquefaction to be a concern. Based on our research we determined that the

Chapter 9: Putting It All Together: An Example Project

Valley Fault System is the governing source for the subject site. The nearest segment of the Valley Fault System is Seismic Source Type C, in accordance with the 1997 UBC, Table 16-U.

4. Earthwork Recommendations All soil and rock material placed by the contractor shall be defined as “engineered fill”. The placement of engineered fill shall be in accordance with this section. All density tests shall be performed by either the sand cone method (ASTM D 1556) or by the nuclear method (ASTM D 6938). We base relative compaction and optimum moisture content of the soil on the most recent ASTM D 1557 test method, with the following exception: Should the fill material consist of more than 30% particles larger than 3/4 in. size, the fill placement should be treated as a rock fill and observed full-time. A project pre-construction (pre-con) meeting is recommended to be held on-site prior to beginning earthwork operations.

4.1 Clearing and Grubbing Before fill placement, all surface vegetation, roots, large boulders, and other debris shall be cleared to a minimum of 5 ft outside of fill areas. Vegetation and any other debris removed from within the cleared area shall be hauled off site. The exposed surface shall then be prepared as described under “Subgrade Preparation.” 4.1.1 Subgrade Preparation Prior to placing fill (including placement in over-excavated areas, roadway cut, and natural surfaces) the existing surface shall be prepared by scarifying to a minimum depth of 6 in.—moisture conditioning to between −1% and +3% of optimum—and then compacting to a minimum of 90% per ASTM D 1557.

4.2 Acceptable Fill Material 4.2.1 Native Material On-site material is acceptable for use as engineered fill; however, placement of material size should be limited to 3" maximum for trench backfill and in the upper 2 ft of building pads. 4.2.2 Import Material Import fill should be free of organic material and debris with rocks no larger than 3" size, be predominantly granular, and have a PI of less than 15, and a low Expansion Index (EI) of ≤50 (per ASTM D 4829). Import material shall be tested for approval by GTOG prior to use on site.

4.3 Engineered Fill Placement All fill shall be placed, tested, and observed in accordance with this section.

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4.3.1 General Fill All soil and rock material placed by the contractor shall be defined as fill. Fill shall be placed and compacted per this section. General fill shall be compacted to 90% of ASTM D 1557 at between –1% and +2% of optimum moisture. All density tests shall be performed by either the sand cone method (ASTM D 1556) or by the nuclear method (ASTM D 6938). The modified Proctor (ASTM D 1557) shall be used for all laboratory reference curves. A vibratory plate whacker (vibra-plate) shall not be used for compacting loose lifts thicker than 3" unless otherwise stated herein. Fill shall contain no material with dimensions greater than 3" size within the upper 24 in. Fill placed in depths deeper than 24 in. below finished subgrade may contain material larger than 3 in. diameter (except trench fill); however, larger material will require observation and placement methods as described under Section 4.3.2. All fill shall be placed in horizontal lifts. Loose lift thickness shall be limited to 8 in. maximum—unless placed as a rock fill. 4.3.1.1 Density Test Frequency: General fill shall be tested at a minimum of one test per every vertical foot, and within each horizontal grid of 300 ft. Trench backfill shall be tested at intervals no greater than each 2 vertical feet and per every100 lineal ft. Roadway finished subgrade and aggregate base shall be tested at a minimum of 1 test per 100 lineal ft. Slope faces shall be tested no less than 1 test each 100 lineal feet and one test every 5 vertical ft. Test locations shall be selected by a representative of GTOG. All fill placed shall be observed and/or tested per the recommendations contained in this report. Any fill areas with a density test failure or fill placed in a manner deemed unacceptable by GTOG shall be reworked to meet recommendations herein. Fill shall not be compacted over unacceptable fill or unprepared native soil. 4.3.2 Rock Fill Rock fill placement shall apply when more than 30% of the material (by weight) is greater than 3/4 in. size, and therefore cannot be tested per ASTM D 1557. Rocks with diameters of 3 in. or larger may be placed in fill areas deeper than 24 in. below finished subgrade. Rock fill lift thickness will be governed by the largest acceptable size material within the fill. Because of the generally untestable nature of the rock fill material, no density testing shall be performed. However, during the placement and compaction of the rock fill, full-time observation is required by a representative of GTOG. Predominantly granular material must be used as matrix soil in rock fills (with the matrix soil being defined as the material finer than 3/4 in. size). The matrix soil shall have an SE of >32 (Sand Equivalency per ASTM D 2419). The rock fill shall be placed so that no voids are visible between the irreducible material and no nesting is apparent. The matrix soil within the rock fill shall be compacted at 2% to 8% above optimum moisture.

Chapter 9: Putting It All Together: An Example Project

Observation trenches shall be excavated as necessary (no less than one per every other lift) to visually confirm adequate densification and to help confirm that the rock fill is free of nested material and/or voids. Should voids, nesting, loose material, or improper moisture content be observed, the unacceptable portion of rock fill shall be remixed and recompacted. 4.3.3 Cut/Fill (Transition) Building Pads Differential support conditions are a concern where foundations span cut and fill soils, or where foundations cross native rock and engineered fill. To help reduce the potential for differential settlement, we recommend that all pads be over-excavated 36 in. and replaced with engineered fill. 4.3.4 Pavement Areas The upper 6 in. of material immediately beneath the aggregate base (AB) section shall be defined as the “subgrade” (SG) section. The surface of the subgrade after passing string lining shall be considered the finished subgrade. Both the subgrade and the AB sections shall be compacted to a minimum of 95% of ASTM D 1557. Preparation and compaction shall be performed as described under Section 4.3.1. All subgrade and AB sections must be stable and free of soft, segregated, nesting, flexing, and pumping areas. Stability of subgrade and AB sections shall be confirmed visually and by proof-rolling, as necessary. Proof-rolling shall be performed with a fully loaded water truck or other means acceptable by GTOG. Aggregate base shall conform to the AB standards listed under Section 6 herein. Finished grade compaction tests (both subgrade and AB) shall be completed and have passed, prior to string lining. Both the finished subgrade and AB surfaces shall be string lined to be within a tolerance of ±1/2 in. Subgrade and AB sections shall not be accepted as complete until surfaces are within the aforementioned tolerances. 4.3.5 Exterior Concrete Flatwork Concrete flatwork such as sidewalks and patios should be placed on 6 in. of compacted AB overlying subgrade in which the upper 6" has been properly moisture conditioned and compacted to a minimum of 95% per ASTM D 1557. Refer to Section 5.3 of this report. 4.3.6 Trench Backfill Utility trenches shall be bedded below the pipe(s) with a 6 in. layer of predominantly granular material, and then compacted to a minimum of 90% of ASTM D 1557. Shading shall be placed around the haunches of pipes and conduits with a cover of 6 in. of shading over the top, compacted to a minimum of 90% of ASTM D 1557. Shading and bedding material shall have a gradation no larger than ¾" size and a PI of less than 15.

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4.4 Unstable Subgrade Mitigation Options Scarify over-wet subgrade soils and allow them to air dry—weather permitting—then remix and recompact. Areas too wet to rework/dry out should be over-excavated a minimum of 18 in. (unless otherwise recommended by a GTOG representative), then covered with an approved woven stabilization fabric—Mirafi 600x or equivalent—and then compacted back to the top of subgrade with AB.

4.5 Slopes The following recommendations should be followed for constructing cut and fill slopes. 4.5.1 Cut Slopes Slopes excavated into undisturbed breccia or conglomerate should be stable if the cut is no steeper than 1.5:1 (horizontal to vertical). However, all cut slopes should be observed by a geologist from GTOG to confirm stability. 4.5.2 Fill Slopes Construct fill slopes to maximum gradient of 3:1. Slopes constructed steeper than 3:1 must be approved by a GTOG Geotechnical Engineer. Figure 4.5.A shows proper benching and keyway construction. Figure 4.5.A. Typical Keyway and Benching Detail

Fill slope construction must begin at the base and be constructed from the bottom up, not pushed out from the top. Slopes should be overbuilt, and then cut back to final design grade. Track walking of slopes is not an acceptable method to achieve slope compaction. Slopes shall be compacted to a minimum of 90% per ASTM D 1557 all the way to the surface. Keying: Fill slopes constructed against existing slopes steeper than 5:1 shall have a keyway placed at the toe. The key width shall be ½ the slope height (or a minimum of 15 ft wide). The toe shall extend a minimum of 2 ft into competent material, as approved by a representative of GTOG. The keyway should slope downward—into the slope—at a minimum of 2%.

Chapter 9: Putting It All Together: An Example Project

Benching: Benching should be performed while placing fill against slopes with a gradient of 5:1 or greater. Benches should be placed every 6 vertical feet—with the bench completely into competent material and wide enough for compaction equipment to work effectively. Subdrainage: Subdrains may be required at the back of some keyways or benches as determined in the field by a representative from GTOG.

4.6 Surface Drainage Slope pavement areas a minimum of 2% toward drop inlets or other surface drainage collection devices. All local and Federal Storm Water and LID practices shall be followed. Slope finished grade away from building exteriors a minimum of 5% for a distance of at least 5 ft. Discharge roof downspouts a minimum of 3 ft away from building to appropriate surface drainage collection devises. Construct V-ditches at the toe of slopes and add one V-ditch for every 20 vertical feet of slope. V-ditches may require rip-rap or concrete lining as determined by GTOG upon review of final plans.

5. Structural Recommendations 5.1 Footings With the understanding that the proposed construction will consist of one or two story, relatively light loaded wood frame buildings with dead plus live wall loads on the order of 1,000 to 2,000 lb per lineal ft (plf); if structural loads in excess of these values are anticipated, GTOG should be contacted to determine if modifications of these recommendations are necessary. A Registered Civil Engineer should design the foundations in accordance with the following recommendations. 5.1.1 Dimensions and Bearing Capacity Continuous strip footings and isolated spread footings are adequate for support of these structures if building pads are prepared in accordance with our Earthwork Recommendations herein (Section 4). Single-Story Foundations Continuous Strip: 12 in. depth, 12 in. width Isolated Spread: 12 in. depth, 18 in. width Two-Story Foundations Continuous Strip: 18 in. depth, 15 in. width Isolated Spread: 18 in. depth, 18 in. width All depths are measured below the lowest adjacent soil/rock grade. Design the foundations recommended above for a maximum allowable bearing capacity of 2,500 lb per sq ft (psf) for dead plus live loads. Increase the

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aforementioned capacity to 3,250 psf for the short-term effects of wind or seismic loading. Prior to placing concrete: • The bottom of foundations should bear on either dense undisturbed native soil or bedrock—or on engineered fill consistent with our Earthwork Recommendations. • Foundations should not span bedrock/fill or native/fill contacts; such zones may cause differential support conditions and should be reviewed by our engineer for proper treatment. • Footings shall be free of loose material, water, ice, or debris prior to concrete placement. • A representative from GTOG should observe the footings of all excavations. 5.1.2 Lateral Resistance A combined lateral resistance from sliding friction and passive pressure can be used along the base and sides of foundations. Use an allowable passive lateral earth pressure of 250 psf per foot of depth. Calculate the sliding friction between the base of foundations and soil by using an allowable coefficient of friction of 0.40. These values include a factor of safety of approximately 1.5. 5.1.3 Settlement Based on the anticipated loads and our analysis, we estimate that total footing settlement resulting from static building loads should be less than 3/4 in., with post-construction differential settlement on the order of 1/2 in.

5.2 Slabs on Grade As a minimum for slab-on-grade construction we recommend the following: 1. Place at least 6 in. of 3/4 in. minus clean crushed rock over the slab subgrade —then settle the rock into place with a minimum of two passes with a vibratory plate. 2. Cover the crushed rock with a 10 mm polyethylene (or equivalent) vapor barrier. 3. Seal the vapor barrier at edges, and at utility and other penetrations. 4. Place 2 in. of sand over the polyethylene moisture barrier; moisten the sand prior to placing concrete. 5. Locate the cold joint between the footing and slab at least 4 in. above the exterior finish grade elevation. 6. Center 6 in. × 6 in. 10/10 (6 × 6 − W2.9 × W2.9) welded wire mesh horizontally in the slab. Support the mesh on dobie blocks; hooking and pulling up the mesh during placement is not acceptable. 7. Use high-quality concrete with a water/cement ratio no higher than 0.55 for floor slabs and a minimum 28 day compressive strength of 4,000 psi. 8. All concrete should be tested in accordance with ASTM standards by an ACI certified technician.

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5.3 Exterior Concrete Flatwork Exterior concrete flatwork, such as sidewalks and patios, should be a minimum of 4 in. thick. Prepare the subgrade as outlined in Section 4.1.1, and then place a 6 in. layer of Caltrans Class 2 AB over the subgrade. Compact the AB to a minimum density of 95% per ASTM D 1557. Flatwork concrete shall have a minimum compressive strength of 3,000 psi. To help control cracking, place expansion and crack control joints per recommendations of the Portland Cement Association. All concrete should be tested in accordance with ASTM standards by an ACI certified technician.

6. Pavement Design We performed a laboratory resistance value (R value) test on the sandy Silt in the northern site area. The R value for this material was 48. No R value test was performed on either the Mehrten breccia or conglomerate. Should either of these materials be used for roadway subgrade, or should an approved import material be utilized, we recommend performing R value testing on each of the materials. We can then adjust our pavement section recommendations accordingly.

6.1 Flexible Pavements (Asphaltic Concrete) We recommend the following pavement sections for traffic indexes 4 through 7, based on a design R value of 48. Traffic Index (TI)

Asphalt Concrete (inches)

Aggregate Base (inches)

4

2

6

5

2.5

6

6

3

7

7

3.5

8

Asphalt concrete paving shall conform to Caltrans Standard Specifications Section 39, for type B. Subgrade shall be prepared as outlined in Section 4.1.1 and compacted to a minimum of 95% per ASTM D 1557. Use Caltrans Class 2 AB in flexible pavement sections. The AB shall be compacted to a minimum of 95% per ASTM D 1557 at a moisture content of between –1% and +2% of optimum moisture.

6.2 Rigid Pavements (Reinforced Concrete) Use rigid Portland cement concrete pavement sections to resist heavy loads and turning forces in areas such as loading docks or lanes, fire lanes, and around trash enclosures. Final design of rigid pavement sections and reinforcement should be performed based on actual traffic loads and frequencies.

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Use Caltrans Class 2 AB in rigid pavement sections. The AB shall be compacted to a minimum of 95% per ASTM D 1557 at a moisture content of between −1% and +2% of optimum moisture. Prior to placing AB, the subgrade shall be prepared as outlined in Section 4.1.1 and compacted to a minimum of 95% per ASTM D 1557. We recommend at a minimum the use of 6" of Portland cement concrete over 6 in. of AB. The Portland cement concrete should have a minimum 28 day compressive strength of 4,000 psi and have 6 in. × 6 in. 10/10 welded wire mesh centered horizontally in the concrete. All concrete should be tested in accordance with ASTM standards by an ACI certified technician.

Chapter 9: Putting It All Together: An Example Project

Figures

Figure 1

Site Vicinity Map

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Site Plan with Trench and Boring Locations

Figure 2

Chapter 9: Putting It All Together: An Example Project

Chapter 9: Putting It All Together: An Example Project

Appendixes Appendix A Trench Logs Appendix B Boring Logs Appendix C Laboratory Test Results

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Appendix A Trench Logs

TRENCH T-1

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TRENCH T-2

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TRENCH T-3

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Appendix B Boring Logs

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Appendix C Laboratory Test Results

LABORATORY TEST RESULTS

Chapter 9 Questions 1. What type of recommendation would not typically be included in a geotechnical report? (a) Pavement thickness (b) Degree of compaction (c) (Height of the structure (d) Footing depth and width 2. Which item is the most important to be performed before any underground work is started? (a) Draw a sketch of the site. (b) Have existing underground utilities located. (c) Decide how many boreholes you will need to drill. (d) Set up a pre-grade meeting. Refer to the Example Geotechnical Report for Questions 3 through 8.

Chapter 9: Putting It All Together: An Example Project

3.

In the Earthwork Recommendations section, which of the following type of soil or conditions was not addressed as a concern? (a) Rock fill (b) Transition pads (c) Expansive soil (d) Bioswale soil (e)None of above

4.

According to the boring and trench logs, at a depth of 1ft. or deeper in the southern portion of the site, expansive soils are expected to be encountered. (a) True (b) False

5.

Cut slopes excavated into undisturbed Mehrten breccia or conglomerate should be stable if cut no steeper than 1:1. (a) True (b) False

6.

Regarding fill slopes, which one of the following statements is false? (a) If a keyway is placed at the toe of a 3:1 slope no benching is necessary while placing the rest of the slope fill. (b) Fill slopes must be built from the bottom up—not pushed out from the top. (c) Track walking slopes for compaction is not acceptable. (d) The keyway shall be a minimum of 15 ft wide and sloped downward into the slope at 2%.

7.

Rock fill placement recommendations shall apply if more than 30% of the material is larger than the No 4 (4.75 mm) sieve. (a) True (b) False

8.

To reduce the potential for differential settlement on this project each pad shall be over-excavated a minimum of 36 in. and replaced with engineered fill. (a) True (b) False

Refer to Project Organization for Questions 9 through 11. 9. In preparation for a project—just before grading—it is wise to pick up samples of both native and import soils (if known) for Proctor samples. (a) True (b) False

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10. The sequential numbering of density tests on a project must be started over on a daily basis beginning at number 1. (a) True (b) False 11. Density test number 142 failed last week, but a retest taken at the same location today passed; however, the last passing test number is now number 215. What is the proper designation for a passing retest of number 142? (a) 215R (b) 142R (c) 216 (d) None of the above

10 Project Site Safety It is crucial that you approach all field work with safety in mind. Safety on the job should never be compromised due to laziness, time, budget, or political pressure. All federal and/or state Occupational Safety and Health Administration (OSHA) guidelines should be followed, as well as local authority and any project-specific safety requirements. If unsure of a safety issue, consult your company’s safety officer or the governing authority.

Trench Safety Never go into a trench that appears unsafe or has not been properly shored or sloped back. Always ensure there is a ladder, stairway, or ramp for easy access into and out of the trenches deeper than 4 ft. Check that the ladder is on firm, level ground and is properly braced or secured before putting any weight on it. Make it a habit to look at the top edges of the trench for any loose rocks, tools, or debris that could fall in while you are working below. Tools and other items must be a minimum of 2 ft. away from the edge of the excavation. Look around to see if any heavy equipment is operating nearby; if so, alert the operator to stop working in your vicinity so that no material can be inadvertently pushed into the trench where you are inspecting or testing. Become familiar with OSHA 29 CFR Part 1926, Subpart P—Excavations.

Trench Safety Guidelines v All excavations (even less than 5 ft deep) must be examined by a “Competent Person” [refer to OSHA Subpart P, 1926.652(a)(1)(ii), OSHA Part 1926.32(f), and OSHA publication 2226-10R-2015—Competent Person definitions]. Even trenches less than 5 ft in depth can be unstable and dangerous, and should be laid back or braced as necessary. There is no statement by OSHA that says that only trenches deeper than 5 ft need to be sloped or shored! v Ensure safe access and egress. Trench excavations deeper than 4 ft require a stairway, ladder, or ramp spaced at no greater interval than 25 ft [refer to OSHA Subpart P, 1926.651(c)(2)]. v Avoid hazardous atmospheres. Adequate precautions must be taken to prevent employee exposure to atmospheres containing less than 19.5%

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v v v v

oxygen or other hazardous atmospheres [refer to OSHA Subpart P, 1926.651(g)]. Always wear a hardhat in excavations. Watch for any overhead hazards, such as loose material or equipment close to the top of the excavation. Understand sloping, benching and bracing; including, the classification of soil or rock type as listed in Appendixes A and B of OSHA Subpart P. Do not enter any trench that has not been properly benched, sloped, or braced.

A Brief on Trenching and Excavation Safety (OSHA publication 2226-10R 2015) The following Soil Classification and Competent Person information is derived from OSHA’s Trenching and Excavation Safety publication. The publication is intended to provide the public with information about OSHA’s Excavations

Figure 10-1

Sloped native soil for safe wall backfill work.

Benched levee bottom for safe fill operation.

Figure 10-2

Appropriately shored trench with chain link fence enclosure Trench shored with ladder for worker egress; Notice the for public protection. unsafe trench crossing by a laborer.

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standards at 29 CFR Part 1926, Subpart P. The OSHA standards apply to all open excavations made in the earth’s surface, including trenches. The Occupational Safety and Health Act requires employers to comply with safety and health standards promulgated by OSHA or by a state with an OSHA-approved state plan. Some of the compliance methods permitted under the excavation standards require a “Competent Person” to classify the four designations of soil rock deposits. The four basic soil classification categories are described following (and are fully listed in OSHA Appendix A to Subpart P of Part 1926 – Soil Classification): Stable rock — Type A soil — Type B soil — Type C soil Stable Rock – a natural mineral matter that can be excavated with vertical sides and remain intact while exposed. Type A – Cohesive soils with an unconfined compressive strength of 1.5 tons per square foot (tsf) (144 kPa) or greater, as tested by a pocket penetrometer (see Table 1-6). Examples include: clay, silty clay, sandy clay, and clay loam. Certain conditions preclude soil from being classified as Type A. For example, no soil is Type A if it is fissured or has been previously compacted or disturbed. Type A can be indented by thumb with “moderate effort.” Minimum sloped trench walls shall be 3/4:1. Type B – Includes cohesive soil with an unconfined compressive strength greater than 0.5 tsf (48 kPa) but less than 1.5 tsf (144 kPa) and granular cohesionless soils (such as angular gravel, similar to crushed rock, silt, silt loam, sandy loam, and, in some cases, silty clay loam and sandy clay loam). Type B can be indented by thumb with “slight effort.” Minimum sloped trench walls shall be 1:1. Type C – Cohesive soil with an unconfined compressive strength of 0.5 tsf (48 kPa) or less, granular soils (including gravel, sand, and loamy sand), submerged soil or soil from which water is freely seeping, submerged rock that is not stable, or material in a sloped, layered system where the layers dip into the excavation or with a slope of four horizontal to one vertical (4H:1V) or steeper. Type C can be indented by thumb “easily.” Minimum sloped trench walls shall be 1½:1.

Who is a Competent Person—Relating to trenches and excavations? A Competent Person is an individual, designated by the employer, who is capable of identifying existing and predictable hazards in the surroundings or working conditions which are unsanitary, hazardous or dangerous to workers, and who is authorized to take prompt corrective measures to eliminate them.

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Under the Excavation Standards, tasks performed by the Competent Person include: • • • • •

Classifying soil Inspecting protective systems Designing structural ramps Monitoring water removal equipment Conducting daily site inspections

(For further clarification, or to report concerns, contact OSHA at 800-321-6742 or www.OSHA.gov—or your local approved State OSHA agency).

Figure 10-3

Unsafe Excavation This is an unsafe excavation to enter, due to the low cohesive, loose sandygravelly, rocky native material. Since drilling a clean hole may have taken more time, the contractor decided to dig a large 8ft. deep square pit to allow room to form the caisson for placement. The foreman then called a geotech firm to send a tech out and take a density test in the bottom, prior to backfilling. Upon arrival, it was apparent to the technician that the excavation was not safe, and he refused to go into it with his nuclear gauge to take a test. The foreman threatened to kick the technician’s firm off the job and hire someone that was “not afraid” to go down and take a test. The tech called his office and informed the project engineer of his concerns. The engineer contacted Cal/ OSHA. Cal/OSHA arrived and after inspecting the site, they “red tagged” the job—until the contractor either safely shored or laid back the walls. The walls were subsequently sloped back to more than a 1½:1. The tech took his test, and grabbed a bulk sample. The backfill testing was then completed safely. The tech made a wise decision by not going into an unsafe excavation. The contractor was ultimately fined by Cal/OSHA.

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Always inform the job foreman of any unsafe situation and discuss any relevant OSHA guidelines or project recommendations (such as laying back slopes to a safer angle). Record all safety-related communications in your daily report. Under no circumstances should you go into a trench or excavation with which you have safety concerns.

Grading Project Safety When driving onto a grading project site, stop and take time to observe the flow of equipment traffic. Sometimes haul roads have only one way or even reverse traffic directions. Keep a safe distance behind heavy equipment since smaller vehicles often cannot be seen when following large trucks, scrapers, and other heavy equipment. While walking across a site or taking tests where dozers, scrapers, or other heavy pieces of equipment are working, always wear a brightly colored safety vest and a hard hat. Make sure that the foreman and/ or the operators are aware that you are testing in the area. Never climb onto a piece of heavy equipment to communicate with the operator. Have the operator stop the equipment and, if necessary, get off their equipment prior to communicating. Do not leave your testing equipment (sand cone, nuclear gauge, etc.) unattended on a job site. The nuclear gauge should

Figure 10-4

Water Truck Sliding off Haul Road Figure 10-4 illustrates what happened when the driver of a water truck chose to drive the haul road before the dozer had completed leveling it. Fortunately, the driver was not hurt when the truck slid off the road. He was doubly lucky, since the day before he had his 10-year-old son riding with him!

Chapter 10: Project Site Safety

always be properly locked and placed securely into your truck bed when not in use. While taking a density test, make sure you are visible to the equipment operators at all times. To help ensure visibility during testing, a lath with a brightly colored ribbon can be placed on top of the spoil pile created from your test hole. Many engineering companies now require flashing warning lights or red flags to be placed on their vehicles while on a grading project. After you have completed taking your test(s), move out of the construction zone before calculating and logging your tests. Avoid potentially unstable cut slopes, such as those created by keyway excavations or temporary in road cuts. Any time you feel that an unsafe condition or situation exists on a job site, immediately withdraw from the area and contact the job superintendent, your supervisor, or other authorized personnel.

Chapter 10 Questions 1.

Trenches less than 5 ft deep are considered safe according to OSHA.

(a) (b) 2.

What type of soil (per OSHA, Subpart P) requires a minimum slope laid back of 1½:1?

(a) (b) (c) 3.

View job photographs daily Perform weekly site inspections Conduct daily site inspections None of the above

When entering a grading project, always drive on the right-hand side of any haul road.

(a) (b) 6.

True False

A Competent Person must:

(a) (b) (c) (d) 5.

Type A Type B Type C

A well compacted non-cohesive soil may be considered a Type A soil.

(a) (b) 4.

True False

True False

When taking a density test, always : : :

(a)

Keep good eye contact and be visible to equipment operators

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(b) (c) (d)

Inform the foreman before taking a test Stay with your test equipment All of the above

7. A cut slope in the back of a keyway is potentially stable.

(a) (b)

False True

Appendix

A Example Municipal Standards The Town of Windsor, California, Earthwork Construction Standards included herein represent standards at the time of this printing; all standards evolve and change over time. However, the following standards are a good example of local municipality standards.

TOWN OF WINDSOR EARTHWORK CONSTRUCTION STANDARDS These Earthwork Construction Standards are incorporated into the Town of Windsor Design and Construction Standards, supplanting Part II Series 300-2 Grading Standards. Any variation(s) from these standards must be approved by the Town Engineer. All standards are to be considered minimums and may be augmented by the Town Engineer. Earthwork Construction includes: Earthwork preparation and construction of roadway, sidewalk, utility foundation and trenches, structural (such as footings, slab, deep and shallow foundations), park area facilities and pathways, drainage and all stormwater related features.

Plans and Permit Prior to performing Grading or Earthwork Construction in the Town of Windsor, a Building Permit and/or an Encroachment Permit must be obtained. The Developer, Agency, Contractor, or Homeowner (applicant) shall contact the Town Public Works Department and/or the Building Department for permit application, procedure, and plan review.

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All Permits and Plans must be reviewed, signed, and approved by the Town Engineer, Building Official, or their representative prior to commencing any construction activities. Earthwork Construction shall be placed and tested in accordance with this section, unless otherwise stated by the Town Engineer, or her/his representative. These standards are to be considered the minimums and may be augmented by the Town Engineer, as necessary.

Fill (definition for these standards) Any soil, rock, or other grading and trench material placed, or previously moved by human forces shall be defined as fill.

Clearing and Grubbing Protected trees or plants, archeological areas, wetland zones, water drainages, endangered species, and any other ‘areas of concern’ must be properly addressed prior to commencing clearing or site work. All differing conditions or findings observed during the clearing and construction phases must be brought to the attention of the Town Engineer. Prior to fill placement, all surface vegetation, boulders, and unacceptable buried debris (structures, tanks, etc.) shall be cleared and removed to a minimum of 5’ (feet) outside of proposed fill or site improvement areas, unless otherwise noted on plans. All vegetation, and any other debris removed from within the cleared area shall be hauled off of the site, unless otherwise approved by the Town Engineer. The exposed surface shall then be prepared as described under “Fill Placement”.

Fill Density Testing The Modified Proctor (ASTM D 1557) shall be used as the laboratory compaction reference, with the nuclear gauge (ASTM D 6938) used for field density determination (percent compaction), unless approved or otherwise stated by the Town Engineer.

Fill Placement The applicant/contractor is responsible to construct the roadway section, pad fill, sidewalk grade, trench bottom, and all other fill areas to meet material, compaction, and other specifications. Prior to placing fill (except for trench bottoms: refer to ‘Trench Fill’) the existing surface shall be prepared by scarifying to a minimum depth of 6″ (inches), concurrently removing greater than 3″ size material, organics, and other debris. The scarified zone shall then be moisture conditioned to between −1% and +2% of optimum moisture, and then compacted to a minimum density of 90% (per ASTM D 1557).

Appendix A: Example Municipal Standards

Native or Imported Fill shall contain no material with dimensions greater than 3″ size, unless specifically approved. Fill that contains more than 30% of the material larger than ¾” size cannot be tested using the Modified Proctor and Nuclear Gauge methods (per ASTM D 1557) and shall be placed under Full-Time Observation (refer to the ‘Rock Fill’ section). Imported soil must meet the same criteria as on-site material, unless otherwise approved by the Town Engineer. Plastic Soil, defined herein as material having a Plasticity Index ≥15 (or an Expansion Index ≥50) shall not be placed within 12″ of footing or pad foundations. Roots, wood and other debris shall be removed from fill soil. Fill shall contain no more than 2% organic material. All fill shall be placed in horizontal lifts. Loose lift thickness shall be limited to 8″ maximum, unless the type of compaction equipment being utilized is proven capable of compacting thicker lifts. Use of thicker fill lifts may only be approved by the Town Engineer. In all cases, the full thickness (depth) of fill must meet compaction specifications, as confirmed by density tests. Compaction shall be achieved by using proper compaction equipment for the structure type, the soil/material type being placed, and site conditions. Should the Town Engineer have concerns regarding the compaction process, the work shall be stopped. A small vibra-plate shall not be used to compact loose fill lift thickness more than 3″.

Unstable fill bottoms must be stabilized prior to placing fill One method to stabilize soft or overly wet material is to Over-Excavate (OX) overly wet/unstable soils; spread, mix, and dry them back—and then re-compact the material between −1% and +2% of optimum moisture to the required density. Another option is to OX the subgrade 18″ below the bottom of the unstable zone, place woven geotechnical fabric for stabilization (Mirafi 600X or equivalent) with a minimum of 18″ overlap at fabric edges. Then compact back 18″ of Aggregate Base (AB) in approximate 3 lifts, with the density increasing by the 2nd or 3rd lift to the planned degree of compaction. Other stabilization options may be considered for approval by the Town Engineer.

General Fill (90%) All non-structural fill placed is considered General fill (unless otherwise stated in these standards) and shall be compacted to a minimum 90% at −1% and +2% of optimum moisture.

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Structural Fill (95%) All structural fill shall be compacted to a minimum of 95% at −1% and +2% of optimum moisture. Material placed within 6″ beneath concrete sidewalk, curb and gutter, paved pathway, foundation bottom, or any material determined necessary for structural support shall be considered structural fill, and shall consist of approved aggregate base (or other material as specified). Prior to placing Aggregate Base, the existing Subgrade shall be scarified 6″, moisture conditioned to between −1% and +2% of optimum moisture and compacted to 95% of the maximum density, unless otherwise approved by the Town Engineer. Controlled Low Strength Material (2 sack cement-sand slurry) may be approved to be used as structural support or trench backfill.

Roadway Fill (95%) The upper 6″ of material immediately beneath the aggregate base section shall be defined as the “Subgrade” (SG) section. The surface of the subgrade after passing String Lining/GPS Surveying (± ½″) shall be considered the finished subgrade (FSG). Each of the 6″ SG and the full AB sections shall be moisture conditioned to −1% and +2% of optimum moisture and compacted to a minimum of 95%. Preparation and compaction shall be performed as described under Fill Placement. Aggregate Base (AB) shall conform to Caltrans Class 2, ¾″ AB specifications, with gradation, R-Value, and SE as shown below. Class 2 Aggregate Gradation Percentage passing

Sieve size 1″

100

3/4″

90 – 100

No. 4

35 – 60

No. 30

10 – 30

No. 200 (fines)

2–9

R-Value = Minimum 78 Sand Equivalent = Minimum 25 (Recycled AB is acceptable, if specifically approved by the Town Engineer.)

Appendix A: Example Municipal Standards

Roadway Stability All Roadway SG and AB must be stable; free of soft, segregated, nesting, or pumping areas. Stability of the subgrade and aggregate base sections shall be confirmed visually by Town Public Works Inspector, (or QA/QC) and by “proof rolling”. Proof rolling shall be performed with a fully loaded water truck. Should a roadway section continue to be unstable; OX of the soft/wet/unstable subgrade and/or native soils shall be performed as described herein, unless other method(s) are approved by the Town Engineer. One method to stabilize soft or overly wet material is to Over-Excavate (OX) the overly wet/unstable soils; spread, mix, and dry them back, and then re-compact the material at −1% and +2% of optimum moisture to the required density. Another is to OX the subgrade 18″ below the bottom of the unstable zone, place woven geotechnical fabric for stabilization (Mirafi 600X or equivalent) with a minimum of 18″ overlap at fabric edges. Then compact back 18″ of Aggregate Base (AB) in approximate 3 lifts, with the density increasing by the 2nd or 3rd lift to the planned degree of compaction. The contractor is responsible to construct the roadway section (and underlying material) to form a stable surface, meeting compaction specifications.

Asphalt Paving No Hot Mix Asphalt (HMA) shall be placed until the surface to receive the HMA has been approved by the Town Public Works Inspector. Contractor QC sampling and testing of the HMA during placement shall be performed per Town of Windsor “Asphalt Placement Standards”, or as determined by the Town Engineer.

Roadway Cut All cut portions of roadway shall be scarified to a minimum of 6″, with all material larger than 3″ size removed. This scarified zone shall than be moisture conditioned to −1% and +2% of optimum moisture and compacted to a minimum of 95%. The SG shall be stable—free of soft, segregated, nesting, or pumping areas.

Trench Fill Outside of paved or concrete areas: The bottom of all trenches shall be compacted to 90% unless otherwise approved by the Town Engineer. Utility trenches shall be “bedded” below the pipe(s) with a minimum 3″ layer of sand,

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and then compacted to a minimum of 90%. Bedding shall be placed around pipes and conduits (haunches), then filled to a minimum of 6″ over the top, and compacted to a minimum of 90%. The jetting of sand will not be allowed unless the Town Engineer specifically approves it. Bedding sand shall be non-plastic with no more than 12% fines and be well graded (per ASTM D 2487). Small vibra-plates will only be accepted for compacting sand, soil, or aggregate thicknesses 3″ or less. Trench areas shall be backfilled and compacted to a minimum of 90% with native or approved material. Trenches may be backfilled with 2 sack cement-sand slurry if prior approval is given by the Public Works Inspector. Inside of paved or concrete areas: The bottom of all trenches shall be compacted to 90% unless otherwise approved by the Town Engineer. Bedding shall be placed around pipes and conduits (haunches), minimum 3″ below, then filled to a minimum of 6″ over the top, and compacted to a minimum of 90%. Trenches beneath structural areas (such as paved roadways, building pads, passing under walls, etc.) shall be compacted to a minimum of 90% to within 6″ of the top of the subgrade soil. The upper 6” subgrade zone, and the overlying A.B. layer (if necessary) shall be placed between −1% and +2% of optimum and compacted to a minimum of 95% density. Unstable and/or saturated trenches shall be enveloped or underlain with either Mirafi 140N (or non-woven filter fabric equivalent) or Mirafi HP270 (or woven geotextile fabric equivalent), respectively. The non-woven fabric is typically used in potentially saturated trenches to limit fines from migrating. The woven fabric may be used for prevention of saturated fines migration and/or stabilization. Trenches may be backfilled with 2 sack cement-sand slurry if prior approval is given by the Town Engineer. All High Voltage Electrical Trenches shall have conduit encased a minimum of 6″ beneath and horizontally, and covered over the top 18″ with red colored 2 sack cement-sand slurry or concrete. The red dye shall be added during the batch mixing, not painted on or mixed in the trench.

Open Trenches and Excavations Open or unfinished trenches (or other excavations) shall be securely covered when no workers are present and enclosed by orange safety fence, or heavier secure fencing as required. Temporary covering for trenches in roadways shall be “non-skid” steel plate, pinned with steel stakes on all sides, and finished with compacted cut-back (cold patch) around the edges for smooth vehicle passage. It is the contractor’s responsibility to have the aforementioned trench plates in position prior to the end of each work day.

Appendix A: Example Municipal Standards

Within 10 working days of the completion of a project, trenches (bell holes, or other excavations) shall be fully restored with asphalt (HMA). Trenches completed in paved areas shall be ‘T’ cut 12″ each side with clean saw cut. If the trench has been backfilled with 2 sack cement-sand slurry, the “T” cut may be waived. Existing AB, AC, and/or concrete sections shall be matched for thickness and material type, unless otherwise specified. SS-1 (or approved equivalent) shall be brushed or sprayed to cover all existing contact surfaces of concrete or asphalt prior to placing HMA.

Trench Safety Excavations must comply with OSHA 29 CFR Part 1926, Subpart P Trench inspections of excavations (per Cal/OSHA, Article 6. Excavations,3.l), including trench walls, the adjacent areas, and protective systems shall be made daily (or more often as necessary) by a competent person. The competent person shall inspect for evidence of a situation that could result in possible caveins, indications of failure of protective systems, hazardous atmospheres, or other dangerous conditions. An inspection shall be conducted by the competent person prior to the start of work and as needed throughout the shift. Inspections shall also be made after every rainstorm or other hazard increasing occurrence. Competent Person Cal/OSHA (Definition): “One who is capable of identifying existing and predictable hazards in the surroundings or working conditions which are unsanitary, hazardous, or dangerous to employees, and who has authorization to take prompt corrective measures to eliminate them”.

Concrete Structural Fill A minimum 6″ layer of Aggregate Base shall be compacted to a 95% or greater immediately beneath all concrete structures, including; Driveways, sidewalks, curb and gutter, catch basins, and other drainage structures, unless otherwise stated in the project plans, specifications, or geotechnical report. AB shall conform to Class 2 AB as listed under ‘Roadway Fill’ of this Earthwork Standard. Prior to placing the AB the upper 6” of the subgrade shall be compacted to 95%.

Concrete Spec’s and Testing “Standard” concrete (sidewalk, curb & Gutter, and other non-structural supporting) shall be 3,000 psi, ¾”, Type II/V. “Structural” load bearing concrete (including footings, piers, and other steel re-enforced concrete) shall meet a minimum compression strength of 4,000 psi (3/4″ or 1″ maximum as job specified), Type II/V.

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All concrete formed with steel must have a minimum of 2” separation from all concrete finish (including footing bottoms and side walls). Steel placement shall be inspected and approved by TOW Inspector (or approved special inspector) prior to scheduling/pouring concrete. All concrete with steel shall be vibrated during pour. All field concrete testing shall be performed by an ACI Certified Grade 1 Technician. Should the material delivered or being placed not meet the project and these standards, the QC, QA, or Town Inspector may reject the material. The material may not be placed (and not re-routed back to the project), or shall be fully removed; as determined by the Town Engineer. All concrete shall be tested per ASTM C94, ACI 301, and ACI 318 procedures, unless otherwise directed or approved by the Town Engineer. A minimum of one set of four cylinders shall be taken per each day, or each separate area of concrete poured; and 1 set per each 50 yds3 thereafter. Four cylinders shall be made for Compression tests (breaks), and shall be made at: (1) 7day, (2) 28 day, and (1) ‘hold’ (to be used if necessary, at a later specified time). The 28-day compression average must meet or exceed the submitted mix deign. Unacceptable material shall be removed. All concrete mix designs must be submitted to TOW Public Works per “Materials and Submittals” as described in these Earthwork Construction Standards.

Foundation Excavations Prior to placement of steel or concrete into foundation bottoms, the foundation excavation must be observed and approved by the Town Public Works Inspector or approved Special Inspector. The foundation must be firm, free of loose material, water, debris, or any other unacceptable material. Foundations must be excavated to the width and depth per plan or project recommendations, and must be founded into dense native soil, or compacted fill. Foundations shall not be founded in plastic soil (P.I. 15 or greater per ASTM D 4813), unless otherwise recommended and designed by a geotechnical engineer. Expansion Index Test(s) may be required to confirm whether the soil has expansive potential, which should then be addressed by the Town or geotechnical engineer. Footings, slabs on grade or other foundations shall not be poured/placed on dried, cracking and/or desiccated soil. Differential support conditions are a concern where foundations span cut and fill soils, or foundations cross native rock and engineered fill. A geotechnical engineer shall be consulted to determine if overexcavation or other methods are necessary to help mitigate differential settlement.

Appendix A: Example Municipal Standards

Slope Fill and Construction Fill constructed against existing slopes steeper than 5:1 shall have a keyway constructed at the slope toe. The keyway width shall be ½ the slope height, or a minimum of 1½ the width of the compaction equipment used. The key bottom shall be excavated sloped into the slope at a minimum of 2%. The toe of the key shall be excavated into dense soil or bedrock formation to a minimum depth of 18”, or as approved by the Town Engineer or the project Geotechnical Engineer. The Key bottom shall be inspected by the Town Inspector or the Project Geotechnical Engineer prior to placing fill. As slope fill is placed, horizontal Benches shall be cut into acceptable dense native soil or compacted fill. Compaction and placement shall be as described under “Fill Placement”. No material with dimensions greater than 3” shall be placed within 1 foot of the slope face.

Oversize Material Placement “Oversize Material Placement” shall apply when more than 30% of the material is greater than ¾″ size, and therefore cannot be tested per ASTM D 1557. Rocks with diameters of 3” or more may be placed in deeper fill areas, as approved by the Town Engineer. The rock fill lift thickness will be governed by the largest acceptable size material within the fill. Due to the generally untestable nature of the rock fill material, no density testing shall be performed. However, during the placement and compaction of the rock fill, full-time observation is required. Predominantly granular material shall be used as matrix soil in rock fills (the matrix soil shall be defined as the material finer than ¾″ size). The matrix soil shall have an SE of >32 (Sand Equivalency per ASTM D 2419). The rock fill shall be placed so no voids are visible between the irreducible material, and no nesting is apparent. The matrix soil within the rock fill shall be compacted at 2% to 8% above optimum moisture. Observation trenches shall be excavated as necessary (no less than one per every other lift) to visually confirm adequate densification, and to help confirm that the rock fill is free of nested material and/or voids. Should voids, nesting, loose material, or improper moisture content be observed, the unacceptable portion of rock fill shall be remixed and recompacted.

Density Testing Frequency Trench Field density tests in fill shall be taken at intervals no less than every 2 vertical feet or 100 lineal feet of fill placed; for trenches shorter in length than 100’, a minimum of two density tests will be necessary. All test locations shall be

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chosen by the testing agency or the TOW Public Works Inspector, not by the contractor.

General Fill Field density tests in fill shall be taken at intervals no less than every 2 vertical feet, or 100 yds3, whichever amount is placed first. No less than two density tests shall be taken on any fill area. All test locations shall be chosen by the testing agency or the TOW Public Works Inspector, not by the contractor. Fill shall not be compacted over unacceptable fill, or unprepared native soil.

Materials and Submittals All materials to be used on construction projects must be submitted for review and approval to TOW Public Works or Building Departments—prior to use. Submittals must include information on the material description, the manufacturer, product specifications, quantity, and any other product information required by the Town Engineer or Building Official. Aggregates, geotechnical fabrics, pipes, concrete, asphalt, steel and all other project specific materials (that are not specified in this Earthwork Construction Standard) shall meet the requirements specified in the project geotechnical report, project plans, or project special provisions.

Sampling and Testing of Soil and Aggregate All sampling procedures for soil and aggregates shall be performed in accordance with current ASTM standard test methods, unless otherwise approved by the Town Engineer. Laboratory and field sampling, testing, inspection or observations, shall be performed by experienced technicians, or other qualified personnel, as approved by the Town Engineer.

Quality Control (QC) and Quality Assurance (QA) Quality Control (QC) refers to the qualified engineering field and lab personnel performing testing and inspection for the general contractor or their subcontractors. Quality Assurance (QA) refers to the Town of Windsor’s selected engineering (or other professional) firm that performs QC review; including sampling, material testing, inspection, and construction procedure documentation and review for the Town of Windsor Public Works and Building Departments. The contractor shall hire an engineering laboratory to sample, test, and document earthworks operations (including backfill, grading, and all other

Appendix A: Example Municipal Standards

materials inspections) required by TOW Standards and/or the project specifications. The engineering laboratory shall perform as contractor Quality Control (QC). It is the Contractor and QC engineering firm’s responsibility to understand current Town of Windsor Public Works Standards and communicate test results to the TOW Public Works in a timely manner. Stoppage of work due to delayed QC test data are the contractor’s responsibility. The contractor shall stop placing, and/or remove any unacceptable material upon notification by the QC engineering lab that the material is out of specifications. Placement shall not resume until the material is confirmed to the TOW Public Works to be back within project specs. Any fill areas with a density test failure, or fill placed in a manner deemed unacceptable by the TOW Public Works Department, their representative, or the QC engineering firm, shall be reworked to meet these standards. Fill shall not be placed over unacceptable fill, or unprepared native soil. The engineering lab (QC) shall submit all testing, sampling, and field observation documentation to the TOW Public Works Engineering Department, as specified in the subheading of this section titled “reports”. The TOW Public Works reserves the right to hire an engineering laboratory of their choice to perform (QA) testing and review. The QA shall have the final determination regarding acceptability of Materials and Procedures. TOW Public Works Department and their QA representative shall be allowed access to all work areas. The QC shall share all project test data, and related project material information with TOW Public Works or their QA. The contractor, or QC shall contact TOW Public Works or their QA to allow for concurrent testing and/ or equal splitting of samples, as necessary. Procedures not conforming to project requirements, or materials not meeting project specifications will be considered rejected and shall be corrected and/or removed immediately; unless otherwise approved by the Town Engineer.

Daily Reports Communication of daily field or lab test data shall be communicated verbally or electronically to the PW Inspector. Depending on the project scope and size, adjustments to the daily/weekly reporting procedures may be adjusted by TOW Public Works Department. At the request of the TOW Public Works Department, QC daily field reports, QC lab reports, or other QC inspection/testing/observation information, shall be submitted for Town Public Works Department review during the construction of a project. Should QC information not be submitted as requested by the Town Engineer or is deemed incomplete or inaccurate; the project may be stopped by the Town Engineer until the required information is submitted.

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Final Reports Within 30 days of completion of an earthwork project, the permittee (or their representative) must submit a PDF report to the TOW Public Works Department. The report shall include daily reports, lab and field data related to the project. Lesser sized reports and or test result data may be accepted dependent on project size; however, any changes to the requirements in this section must be prior approved by Town Engineer. The final laboratory/field report shall be signed by a registered civil or geotechnical engineer, or a NICET Level IV Technician (Materials or Geotechnical), unless otherwise approved by the Town Engineer. Final reports shall include a statement that “All earthwork and materials placed were completed in general accordance with Town of Windsor “Earthwork Construction Standards”. Any exceptions or non-compliances shall be stated in the report. All reports shall be submitted to the TOW Public Works Department within 30 days after the completion of construction.

ADA Ramps and Crossings, and other Details The most current Cal Trans Details (including A88A) shall be implemented during all construction, unless otherwise approved by the Town Engineer.

Entrance/Exit Cobble (Refer to TC-1 in the CASQA Stormwater BMP Handbook) 3″ to 6″ size angular cobble stone shall be placed over a woven geotechnical fabric (Mirafi 600X or equivalent). Prior to the placement of the woven fabric, the area of placement shall be excavated to allow for a minimum of 12″ thick section of cobble to be placed. This area of cobble entry shall be a minimum of 12′ wide by 50′ in length. The cobble entry shall be maintained by the contractor to remove mud/dust or other material buildup from within the 12” section.

Storm Water and Pollution Control (Refer to current EPA and CASQA Stormwater Standards and BMP’s) Construction work within the Town of Windsor shall fully comply with all current EPA Storm Water Pollution Prevention Plan (SWPPP), the California Department of Transportation Storm Water Management Plan, The California Regional Water Quality Control Board, National Pollutant Discharge Elimination System (NPDES), and current CASQA Best Management Practices (BMP), along

Appendix A: Example Municipal Standards

with all other environmental quality and monitoring necessary. This includes all LID Structures.

Health and Safety (Refer to Federal OSHA and Cal OSHA current Standards) At any time that the Public Works Inspector or the Town Engineer’s representative deem that the materials, workmanship, are a safety concern, the job may be stopped immediately. During the construction process, all applicable “OSHA Standards for the Construction Industry” shall be followed, including (but not limited to) 29 CFR Part 1926, Subpart P – Excavations. The Contractor performing the work shall supply a “ Competent Person” per all CAL/OSHA Safety Requirements, not limited to, but including excavations. All construction equipment and materials shall be safely fenced off from public access during the entirety of the project. Knowing and following Cal OSHA Safety Standards is the contractor’s responsibility. TOW Public Works may stop construction on a project at any time until safety concerns have been corrected. During construction the contractor shall supply the work area (job site) with a minimum of one porta-toilet, and more as necessary or directed by the TOW Public Works Inspector for larger projects.

Dust Control (Refer to: Northern Sonoma County Air Pollution Control District) “Rule 430” Fugitive Dust and airborne particulate must be limited in all areas that a contractor is performing construction, or where equipment is driven to access the work area. A) “The handling, transporting, or open materials in such a manner which allows or may allow unnecessary amounts of particulate matter to become airborne, shall not be permitted” B) “ Reasonable Precautions must be taken to prevent particulate matter from becoming airborne”, including, but not limited to: * ‘Covering open bodied trucks : : : ’ * ‘The prompt removal of earth or other material from paved streets onto which earth or other material has been transported by trucking or earth moving equipment, erosion by water, or by other means.’

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The Town of Windsor Public Works may stop a project until dust and debris have been properly controlled, and an acceptable method of dust control has been established.

Traffic Control (Reference the current CA MUTCD) Traffic Control Plans (TCP’s) must be submitted to Town of Windsor Public Works Department for review prior to beginning any work that may in anyway affect the flow or safety of either pedestrian, vehicular, or bicycle traffic. All TCP’s must be specific to the location of the construction site. All TCP’s must be reviewed and approved by the Town Engineer or their representative prior to receiving any related Encroachment, Building, or other affected Town permit. To ensure that the traffic control device practitioner is designing TCP’s and performing ‘Work Zone Traffic Control’ safely, the most current California Manual on Uniform Traffic Control Devices (CA MUTCD) shall be referenced. The most current edition of the Work Area Control Handbook (WATCH) is a good reference. CA MUTCD, and other related information is available on the Internet at the following web link: http://www.dot.ca.gov/camutcd Prior to a Contractor being approved to perform Work Zone Traffic Control, the Town Engineer may require documentation to help confirm the qualification, experience, flagger certification, and training necessary to perform the planned project. Any traffic control contractor that does not follow the approved TCP, or puts the public in danger in any way, can be removed from a project by the Town Inspector or Engineer at any time. The job will be stopped until the necessary TCP procedures and a qualified contractor is approved. Should the Town Engineer become concerned about a change in traffic, pedestrian, weather, lighting, or any other condition that may adversely affect safety; the work may be stopped immediately. The Traffic Management Contractor shall make all corrections required by the Town Engineer, prior to re-commencing work.

Town of Windsor, California Public Works, Engineering Department

Appendix

B Answer Keys Chapter 1 1. Porosity of a soil may indicate that the soil is: (a) Well graded (b) Engineered fill (c) A natural formation 2. Sand particles will not pass what size sieve? (a) No.200 (0.075 mm) (b) No. (4.75 mm) (c) No. 100 (1.50 mm) 3. A soil composed of 65% sand, 30% silt, and 5% clay could best be described as a: (a) SC (b) SM (c) ML (d) None of the above 4. A soil composed of 50% sand, 25% clay, and 25% silt could best be described as a: (a) CL/ML (b) SC/SM (c) SM/CL 5. Which of the following are good indicators that a soil is more clayey than silty? (a) Light in color and porous (b) Low dry strength and feels soft when wet (c) High dry strength and no dilatancy reaction (d) None of the above

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6. Which two examples best describe an artificial fill type of soil? (a) Naturally deposited material, such as alluvial or slide debris (b) Soil with construction debris (glass, brick, etc.) (c) Documented engineered fill (d) Porous topsoil 7. A soil classified by the USCS symbol of CH would have which two characteristics? (a) Finer than the No. 200 sieve (b) High porosity (c) High dilatancy (d) High plasticity

Chapter 2 1. One main advantage of a ring sampler over an SPT sampler is: (a) Gradation tests can be performed only on a ring sample. (b) Ring samples are considered relatively undisturbed, allowing for more varied lab testing. (c) Moisture tests are more accurate when performed on ring samples. 2. Which exploration technique is the best to observe shallow geologic strata? (a) Backhoe trenching (b) Split barrel sampling (c) Tube sampling 3. Choose the two best methods for determining excavatability of rock. (a) Ripping with single shank dozer (b) Split barrel sampling (c) Tube sampling (d) Seismic Refraction Survey 4. A blow count of 23 for an SPT sampler driven into a sandy soil would indicate: (a) A relative density of “medium” (b) Refusal (c) A relative consistency of “stiff”

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5. A seismic velocity of 2100 ft/s would indicate to the contractor that blasting is necessary. (a) True (b) False 6. During removal of rings from the ring sampler barrel it is best to hit the barrel with a hammer to loosen the rings. (a) True (b) False

Chapter 3 1. Which type of Proctor uses a 10 lb hammer and an 18 in. drop? (a) The original Proctor proposed by R. R. Proctor (b) The modified Proctor (ASTM D1557) (c) The standard Proctor (ASTM D698) 2. ASTM D1557 method A uses which screen to pass material through? (a) NO. 200 (b) NO. 40 (c) NO. 4 3. Optimum moisture is the point that: (a) A sandy soil should be screened across the No. 4 sieve (b) A fine-grained soil becomes liquid (c) Soil will compact best in both the field and laboratory (d) No more water can be retained in a soil 4. Sodium hexametaphosphate is used to: (a) Remove dry soil from dirty sieves (b) Deflocculate fine soil during a hydrometer test (c) During a Proctor test, to help reach optimum moisture (d) None of the above 5. The hydrometer analysis is used to determine the particle size distribution of: (a) Sand, clay, and silt (b) Sand and colloids (c) Material finer than the No. 200 sieve (d) None of the above

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6. Hydrometer readings should always be taken at the top of the meniscus. (a) True (b) False

Chapter 4 1. The sand cone test uses No. 10 silica sand: (a) True (b) False 2. The (a) (b) (c) (d)

depth of the hole dug for the sand cone test should be: 2 to 4 in. 4 to 6 in. 3 to 5 in. None of the above

3. After the sand has stopped flowing from the sand cone jar during a test, you should firmly tap the jar: (a) True (b) False 4. The neutron source of the nuclear gauge is depleted Uranium 238 and is relatively harmless: (a) True (b) False 5. A sand cone test may be performed on a sloped surface: (a) True (b) False 6. A nuclear gauge test may be performed on a sloped surface: (a) True (b) False 7. As long as the nuclear gauge is locked in its storage box at the rear of a pick-up truck, it is OK to sit on the tailgate near the gauge. (a) True (b) False

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8. Which of the following soils, or test situations, may bias or cause the gauge to give an inaccurate moisture result? (a) When testing gypsiferous soil (b) When testing diatomaceous soil (c) When testing backfill in a 30 in. wide trench (d) All of the above (e) None of the above

Chapter 5 1. Information in a geotechnical report often includes at least two of the following recommendations: (a) The over-excavation of all sandy soils (b) Preparation prior to fill placement (c) Removal of unacceptable material (d) Strict equipment type criteria 2. Expansive soils are often compacted at lower densities and higher moistures. (a) True (b) False 3. Pumping or deflection of clayey soil is acceptable in roadway subgrade. (a) True (b) False 4. The backscatter method of testing with a nuclear gauge should not be used when testing a thin layer of aggregate base. (a) True (b) False 5. Which two conditions are desirable across a footing bottom? (a) Dense native soil (b) Compacted fill contacting bedrock (cut/fill condition) (c) CL/CH soil at under-optimum (d) Compacted fill soil

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6. A caisson was drilled to a depth of 60 ft, and upon completion water had seeped in and filled up 15 ft of the hole; what is the proper action to take prior to pouring concrete? (a) Remeasure the hole, and then use a vac-truck to remove the water (b) Confirm that the contractor will place a tremie to the bottom of the caisson during the pour. (c) Pour low-slump concrete from the top of the caisson, making sure to vibrate from the bottom of the hole during the pour. (d) Calculate the amount of concrete necessary to fill the caisson, with no adjustment made for the 15ft. of water.

Chapter 6 1. Which of the following areas should a geologist be asked to inspect? (a) Keyway excavations (b) Cut slopes (c) Footing excavations in compacted fill (d) A and C (e) A and B 2. It is not the technicians’ responsibility to be aware of geologic conditions. (a) True (b) False 3. Daylighted bedding may be observed as strata in a cut slope that dips into the slope face. (a) True (b) False

* No Questions for Chapter 7 * Chapter 8 1. While reviewing a geotechnical report in preparation for a new project, which item would be least important to the geotechnical technician? (a) Whether old fill or foundations exist on site (b) Recommendations for the degree of compaction (c) The height of the structure(s) (three, four stories, etc.) (d) Whether there are transition (cut/fill) lots

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2. At the pre-grade meeting, safety should not be discussed by the technician. (a) True (b) False 3. A vibra-plate is best for compacting lifts of clay. (a) True (b) False 4. If a certain type of compaction equipment is not working well, it is permissible to suggest other options to the contractor. (a) True (b) False 5. Which of the two following grading processes are important for the geotechnical technician to observe? (a) The proper maintenance of the compaction equipment (b) Benching into slopes during fill placement (c) Depth of removals and over-excavations (d) Placement of a benchmark by the surveyors 6. The wearing of a safety vest is necessary only during roadway projects. (a) True (b) False 7. Density tests should never be taken before or after a contractor begins or stops work for the day. (a) True (b) False

Chapter 9 1. What type of recommendation would not typically be included in a geotechnical report? (a) Pavement thickness (b) Degree of compaction (c) Roof type of the structure (d) Footing depth and width

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2. Which item is the most important to be performed before any underground work is started? (a) Draw a sketch of the site. (b) Have existing underground utilities located. (c) Decide how many boreholes you will need to drill. (d) Set up a pre-grade meeting. 3. In the Earthwork Recommendations section, which of the following type of soil or conditions was not addressed? (a) Rock fill (b) Transition pads (c) Expansive soil (d) Bioswale Soil (e) None of above 4. According to the boring and trench logs, at a depth of 1 ft or deeper in the southern portion of the site, expansive soils are expected to be encountered. (a) True (b) False 5. Cut slopes excavated into undisturbed breccia or conglomerate should be stable if cut no steeper than 1:1. (a) True (b) False 6. Regarding fill slopes, which one of the following statements is false? (a) If a keyway is placed at the toe of a 3:1 slope no benching is necessary while placing the rest of the slope fill. (b) Fill slopes must be built from the bottom up—not pushed out from the top. (c) Track walking slopes for compaction is not acceptable. (d) The keyway shall be a minimum of 15ft. wide and sloped downward into the slope at 2%. 7. Rock fill placement recommendations shall apply if more than 30% of the material is larger than the No. 4 (4.75 mm) sieve. (a) True (b) False

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8. To reduce the potential for differential settlement on this project each pad shall be over-excavated a minimum of 36 in. and replaced with engineered fill. (a) True (b) False Refer to Project Organization for Questions 9 through 11. 9. In preparation for a project—just before grading—it is wise to pick up samples of both native and import soils (if known) for Proctor samples. (a) True (b) False 10. The sequential numbering of density tests on a project must be started over on a daily basis beginning at number 1. (a) True (b) False 11. Density test number 142 failed last week, but a retest taken at the same location today passed; however, the last passing test number is now number 215. What is the proper designation for a passing retest of number 142? (a) 215R (b) 142R (c) 216 (d) None of the above

Chapter 10 1. Trenches less than 5 ft deep are considered safe according to OSHA. (a) True (b) False 2. What type of soil (per OSHA, Subpart P) requires a minimum slope laid back of 1½:1? (a) Type D (b) Type C (c) Type A

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3. A well compacted non-cohesive soil may be considered a Type A soil. (a) True (b) False 4. A Competent Person must: (a) View job photographs daily (b) Perform weekly site inspections (c) Conduct daily site inspections (d) None of the above 5. When entering a grading project, always drive on the right-hand side of any haul road. (a) True (b) False 6. When taking a density test, always : : : (a) Keep good eye contact with, and be visible to equipment operators (b) Inform the foreman before taking a test (c) Stay with your test equipment (d) All of the above 7. A cut slope in the back of a keyway is always stable. (a) False (b) True

Appendix

C Glossary of Geotechnical Related Terms AASHTO: American Association of State and Highway Transportation Officials

Adsorption: The process by which water molecules or ions are attached to the surface of soil particles

Abrasion: The process of wearing away by erosion, caused by continuous friction from the actions of wind, water, or ice

Aeolian (Eolian) Deposits: Rock and soil constituents that have been carried and laid down by wind currents, such as sand dunes and loess deposits

Absorbed Water: Water that has soaked into—and is being held inside—a soil or rock mass

Aggregate: Sand, gravel, or other coarse mineral material; fine aggregate is material that will pass the No. 4 sieve, whereas coarse aggregate is retained on the No. 4 sieve

Absorption: The uptake of fluid into an interstitial space, similar to the manner in which a sponge takes in water

Aggregate Baserock (Aggregate Base, AB, or Aggregate Base Course—ABC): A mixture of gravel and sand with some fines, typically used between the subgrade and asphalt; specific gradation, durability, and other criteria are set for various uses, and the specified material may be designated by various classes or types of AB.

ACI: American Concrete Institute Acid Soil: Soil with a pH value less than 7 Adhesion: The shearing resistance between soil and another material under zero externally applied pressure

Aggregate Subbase (ASB): A mixture of sand gravel and some fines similar to aggregate base—except that more fines may be allowed, with less-stringent durability requirements

Admixture: Materials or chemicals added to concrete (other than water, cement, or aggregate) used to entrain air or to retard or accelerate the setting time

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Alkali: A mixture of calcium, potassium, and sodium, often common in dried-up lake deposits, typically, white in color Alkaline Soil: Soil with a pH value greater than 7 See Alkali. Allowable Bearing Pressure: The maximum pressure that can be permitted on a foundation soil—allowing for an adequate safety factor against rupture of the soil mass, or movement of the foundation of such a magnitude that the foundation is damaged Alluvium: A term used to describe sediment deposited on land by running water. It may occur in deposits on terraces, flood plains, or deltas, or as a (alluvial) fan at the base of a slope Angle of Obliquity: The angle between the direction of the resultant stress (or force) acting on a given plane and the normal to that plane Angle of Repose: The maximum angle that a granular material can be loosely stockpiled or accumulate and remain stable—the point at which any additional material will cause the pile to collapse from the influence of gravity; measured from the horizontal Angular Particle (Grain Shape): Particles (rock, gravel, or sand) that possess well-defined edges formed at the intersection of roughly planar faces Anhydrous: A material that has an affinity for water because the water in its crystalline structure has been removed

Anisotropic Mass: A soil or rock mass that has different physical properties when the direction of measurement is changed; commonly used in conjunction with permeability change that varies with direction of measurement Approval: A written engineering or geologic opinion (report) concerning the progress or completion of work See Certification. Aquiclude: A soil mass or rock layer that, owing to its low permeability, limits the flow of water Aquifer: A layer of permeable rock or soil in which groundwater flow is sufficient to supply wells or springs Aquitard: A confining bed that retards—but does not prevent—the flow of water between an adjoining aquifer; a leaky confining bed Arching: The transfer of stress from a yielding portion of a soil mass to adjoining less yielding material Arcuate Path: A curved or circular path through a homogeneous soil mass along which failure might occur Arroyo: A desert gully with near vertical banks Artesian Water: Water under pressure in an aquifer beneath an impermeable rock layer; when drilled into, artesian water will rise without pumping Artificial Fill (AF): Earthen material, debris, or other matter placed by human forces

Appendix C: Glossary of Geotechnical Related Terms

As-Graded (As-Built): The surface or utility conditions existing at the completion of a grading or construction project Asbestos: A fibrous mineral (chrysotile serpentine) that can be separated into long spinnable fibers that are heat resistant and are chemically and electrically inert. Asbestos is a known carcinogen and should be handled with care. ASCE: American Society of Civil Engineers. Founded in 1852, ASCE is the nation’s oldest engineering society, representing more than 150,000 members of the civil engineering profession in 177 countries. Ash Content: Percentage by dry weight of material remaining after organic soil (such as peat) is burned by a standardized method Asphalt (AC): A dark brown to black cementitious material, solid or semisolid in consistency, in which the predominating constituents are bitumens that occur in nature or are obtained as residue in refining petroleum ASTM International (American Society for Testing and Materials): Organized in 1898, ASTM has grown into one of the largest voluntary standards development systems in the world. ASTM members write standards for materials, products, and services, including methods for performing soils and materials tests, each of which are described in detail in their annual books of standards.

Index for properties of silty and clayey soils (refer to ASTM D4318); (2) originally described by Albert Atterberg in 1912 as the collective designation of “seven limits of consistency” of fine-grained soils Auger: A spiral shaped tool (which may vary in length) used to drill soil or soft rock, which may be solid or hollow-stemmed; the hollow-stem type allows for sampling without removing the auger from the borehole. Back-cut: The face of an excavated slope prior to the placement of fill, wall, or other structure against it Backfill: (1) The process of placing material back into an excavation; (2) the material used to refill an excavation Basalt: A very fine grained dark gray or black volcanic rock, often with gas bubbles or vesicles Base Key: See Key. Base Rock (Basecourse/Base Course): See Aggregate Baserock. Bearing: The stress between a foundation and its support; the load carried by the supporting material Bearing Pile: A pile that carries weight (load), as opposed to earth pressure (friction) Bearing Value: The load on a bearing surface divided by its area

Attenuation: The reduction of amplitude with time and distance

Bearing Wall: The structural wall that supports part of the load from above and transfers the load down to a lower floor or footing

Atterberg Limits Test (Chapter 3): (1) Current usage refers to the Liquid Limit, Plastic Limit, and the Plasticity

Bedding: (1) Stratum of sedimentary rock exhibiting surfaces of separation (bedding planes) between layers

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of the same or different materials— such as shale, siltstone, sandstone, etc.; (2) A select material on which a utility pipe is placed—such as sand or base rock Bedrock: Rock of relatively great thickness and extent, in situ. May be overlain by soil or exposed at the surface Bench: A relatively level step, excavated into acceptable material of a slope face, against which fill is to be placed. Its purpose is to provide a firm and stable contact between the existing material and the new fill soil to be placed. Benchmark (BM): A survey marker that indicates a specific location and elevation Bentonitic Clay (Bentonite): Clay with a high content of the mineral montmorillonite, characterized by high swelling upon wetting. It is formed by the decomposition of volcanic ash and commonly used as drilling mud during rotary wash drilling, or to help occlude water migration through dam and levee structures. Berm: A relatively low, narrow mound of soil of variable length used to divert water. The berm may be covered with rip rap or other materials to help prevent its erosion Binder: (1) The portion of the soil passing the No. 40 (425 μm) sieve; (2) anything that causes cohesion (such as clay or cement) in loosely assembled substances Bio-retention Soil (Bio-retention Soil Medium, BSM, Bio-Soil): A soil mixture used in an LID feature—such as a bioswale or infiltration trench—that is sufficiently

permeable (having a specified infiltration rate) and has adequate properties and moisture retention to support healthy vegetation Bioswale (Bioretention Trench, Infiltration Trench): Drainage courses and linear channel features placed to maximize the time that stormwater runoff may be retained in the feature while concurrently reducing the pollutants, silts, and debris exiting the features while replenishing the natural water aquifer. Bioswales are typically vegetated over underlying layers of BSM, gravel/ sand mixes, and perforated underdrain pipe. They are an integral part of many LID designs. Bit: A device that is attached to the tip of an auger, drill rod, or a wire line that is used as a cutting tool to penetrate soil or rock; power may be applied to the bit percussively or by rotation. Blade: Slang term for road grader Blanket Grouting: A method in which relatively closely spaced holes are drilled and grouted in a grid pattern over an area for the purpose of making a soil stratum stronger and less pervious Blending: A term describing the intermixing of different soils—often used to reduce expansive characteristics, or to reduce the percentages of minerals (such as gypsum) in the engineered fill Block Retaining Wall: Composed of interlocking concrete blocks integrated with a drain system of gravel and a retaining system of geosynthetic fabric; designed to retain a slope of potentially unstable soil or rock

Appendix C: Glossary of Geotechnical Related Terms

Blue Top: Slang for finished grade elevation, usually indicated by blue colored hubs or feathers (blue tops) placed by surveyors to guide the grading contractor in the final grading operations BMP (Best Management Practices): These are considered good “housekeeping practices” that are implemented in the Storm Water Pollution Prevention Plan (SWPPP), and other storm water control programs. BMPs may be “non-structural”—such as training, moving materials of concern inside, and implementing spill prevention plans, or “structural”— including placement of swales, filtration devices (silt fences, rock bags, straw wattles, etc.), covering stockpiles, and other methods to limit pollution and/or turbid discharges and runoff Bog: A mossy or peat-covered area with a high-water table Bone yard: A slang term used by grading contractors describing the area or location on the job site where their heavy equipment (dozers, blades, backhoes, etc.) are parked when not in use Borehole: A hole made while drilling, such as for oil, soil, or rock sampling Borrow Material (Import Material): Soil, rock, or other fill material that is obtained from an off-site location to be used in the grading or filling on the project Bottom: Refers to the area at the lowest point of removal (over-ex, OX) prior to the preparation and then placement of fill Boulder: A rock fragment—larger than a cobble—with minimum

dimensions of 12 in., the edges of which are usually rounded by weathering or abrasion Breccia: A clastic sedimentary rock composed of angular fragments of older rocks cemented together Bridging: (1) The transfer of stress from a yielding (typically pumping) area of soil to an upper adjoining soil mass; (2) a process of compacting selected materials over soft or pumping soils BSM: See Bio-retention Soil. Bulkhead: A steep or vertical structure supporting a natural or artificial embankment Bulking: (1) Increase in volume of fine grained soils caused by the addition of moisture; (2) increase in volume of a material during excavation Bulldozer (Dozer, Cat): A large track driven machine with a blade in the front, used to push soil, rock, or other materials Burrito Drain: Drainpipe and drainage rock wrapped by filter fabric— similar to how a burrito is wrapped Buttress (Buttress Fill): An engineered fill—usually designed based on a slope stability analysis—built to support a weak or unstable slope or other soil mass Caisson: A cylindrical shaft drilled into competent material, the bottom of which may be reamed into a bell shape (belled caisson) to provide a larger base for foundation support. The shaft may then be reinforced with steel and filled with concrete.

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Calcareous: Indicating a material composed essentially of calcium carbonate (such as limestone) or cemented by calcium carbonate; it will fizz when touched with a drop of dilute hydrochloric acid (HCl). Calcite: A mineral; calcium carbonate (CaCO3), the principal mineral in limestone Caliche: Typically, a light-colored material composed primarily of calcium carbonate, varying in amounts of clay and in degree of cementation; generally found in deserts at shallow depth in layers of varying hardness Cap Rock: A more impervious harder rock that overlays a softer or more weathered rock Capillary Action: The rise or movement of water through the porous structure (interstices) of a soil or rock formation, caused by the difference between the relative attraction of the water molecules for each other and for those solid; may be compared to the flow of water into a sponge, when the sponge is partially immersed in water Capillary Break: Indicates a layer of material that resists the vertical movement of water, such as gravel Capillary Head: The potential that causes water to flow by capillary action; expressed in head of water Casing: A pipe (typically steel) welded or screwed together and lowered into a borehole to help prevent the entry of gas or liquid, or the caving of loose material inside the boring; casing may also be used to help limit the loss of circulation fluid while drilling in a porous, cavernous,

or otherwise crevassed soil or rock formation (e.g., a hollow-stem auger may act as a type of casing) Cast in Place: Concrete or other cementitious material poured in place Cat: The trademarked name for any machine made by the Caterpillar Tractor Company; widely used to indicate any crawler type tractor, or slang for bulldozer (dozer). Catch Basin (D.I. or Drain Inlet): A complete drain box made in various sizes that is typically placed along paved roadways to collect surface water Cathead: A deep flanged, spool-like winch or capstan mounted to one side of the swivel head of a drill rig. It may be used to wind a line when lifting rod, casing, pipe, or to operate a drive hammer Cement (Portland Cement): Consisting of four primary chemical compounds: tricalcium silicate, dicalcium silicate, dicalcium aluminate, and tetracalcium aluminoferrite. When proper proportions of these compounds are mixed together with water, sand, and gravel, a hardening process begins—with strength increasing over time. Cementation: The deposition of mineral solution into the intergranular space (interstice) of sedimentary rock. he most common mineral cements are calcium carbonate, silica, and iron oxide. Certification: A written engineering or geologic opinion (report) concerning the completion of related earthwork

Appendix C: Glossary of Geotechnical Related Terms

Check Valve: A ball type valve placed in core barrels, soil samplers, or drill rods to control the directional flow of liquids. When used in a drive sampler, a check valve may help stop drilling mud from washing out lowcohesion or non-cohesive soil from the sampler during recovery.

liquid limits test. Further size definition can be made by a hydrometer analysis, where clay is defined as the particles between 1 and 5 μm in size.

Chemical Grout: Any grouting material characterized by being in true solution, having no particles in suspension

Cleavage: The tendency to break along roughly parallel planes, related to the bedding planes of a rock formation or the crystal structure of a mineral

Chip Seal: A binder application that is placed in the form of an emulsion or hot spray and then overlain by a layer of fine aggregate/medium to coarse sand—typically placed over an existing paved surface to improve drivability and extend the life of the pavement Choker: A windrow of material placed along a road shoulder during the grading process Circulating Fluid: A fluid (drill mud, water, etc.) pumped into a borehole through the drill stem, the flow of which cools the bit, washes away cuttings from the bit, and transports cuttings out of the borehole Clastic: A rock primarily composed of broken fragments or grains of preexisting rocks or minerals cemented together, such as sandstone or conglomerate Clay (CL): A fine grained soil or the fine-grained portion of a soil that can be made to exhibit plasticity within a range of water contents and that exhibits medium to high dry strength when air dried. Clay particles are a portion of the fines passing the No. 200 sieve (75 μm) and must plot above the “A” line on the plasticity chart as defined by the plastic and

Clean Soil: Indicating less than 5% of the soil passing the No. 200 sieve

Cleft Water: Water that exists in or flows through geological discontinuities in a rock formation Cobble: A rock fragment with dimensions between 3 and 12 in. (between gravel and boulder size) Coefficient of Curvature (Cc): Part of the formula used to determine whether a predominantly sandy or gravelly soil is well or poorly graded; Cc = [(D30)2]/(D10 × D60), where D10, D30, and D60 are the particle size diameters corresponding to the points where 10%, 30%, and 60% material passes on the cumulative particle-size distribution curve (refer to ASTM D2487 for cumulative particle size plots) Coefficient of Uniformity (Cu): Part of the formula used to determine whether a predominantly sandy or gravelly soil is well or poorly graded. Cu = D60 / D10, where D10 and D60 are the particle-size diameters corresponding to the points where 10% and 60% material passes on the cumulative particle-size distribution curve (refer to ASTM D2487 for cumulative particle size plots). Cohesion: All the shear strength of a soil not resulting from friction;

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cohesion can be pictured as an inherent tensile force that arises from the attraction that exists among very small particles. Cohesionless Soil: A soil that when unconfined has little or no strength when air dried (non-cohesive) and has little or no strength when submerged in water (such as a clean sand) Cohesive Soil: A soil that when unconfined has strength when air dried and has significant strength (cohesion) when submerged in water (such as clay) Cold Joint: A separation in a concrete structure caused by two placements at a time interval great enough to allow one portion to cure prior to the placement of the adjoining section. Standard practice is to separate cold joints with fiber or other products. Colloid: A particle with a diameter less than 1 μm (a smaller size than clay) Colluvium: A loose rock material and/or soil mass deposited by water, downslope creep, or rapid processes such as landslides and mudflows; colluvium is formed on slopes with the thickest deposit generally at the slope toe. Compaction: The densification of fill (soil or other material) through mechanical manipulation (tamping, rolling, vibrating, etc.) resulting in a decrease in volume (void space); the addition of optimum amounts of water during the compaction process is crucial to obtaining adequate densification of the material. Compaction Curve (MoistureDensity Curve, Curve): The curve

created by the laboratory “maximum density test” that shows the relationship between the dry unit weight (density) and the moisture content of a soil for a given compactive effort; the plots of the maximum dry density and optimum moisture meet at the top of the curve. Compaction Test: See Density Test. Competent Material: (1) Earthen materials that are capable of withstanding the loads that are to be imposed on them without failure or detrimental settlement; (2) material approved for use as engineered fill by the project specifications or as recommended by the geotechnical engineer Competent Person: (1) Someone capable (through experience and training) of identifying existing and potential hazards arising during construction—that may either expose workers or the general public to unsafe conditions—and has the authorization to eliminate them; (2) OSHA 2226-10R-2015 publication referencing 29 CFR Part 1926, Subpart P and Excavation Standards. Some of the compliance methods listed under the excavation standards require a “competent person” to classify the four designations of soil rock deposits and conditions exposed during trenching or excavation, including • • • • •

Classifying soil, Inspecting protective systems, Designing structural ramps, Monitoring water removal equipment, and Conducting daily site inspections.

Compressibility: The property of a soil pertaining to its susceptibility to decrease in volume when subjected to load

Appendix C: Glossary of Geotechnical Related Terms

Compressive Strength: The load per unit area at which an unconfined cylindrical specimen of soil or rock will fail in a simple compression test Conchoidal: Shell shaped, with a smooth curved surface; certain rocks, such as flint and obsidian, and minerals such as chalcedony and quartz, when fractured, leave a conchoidal surface. Conglomerate: A clastic sedimentary rock consisting of rounded stones (typically gravel and cobble size) that are cemented together Connate Water: Water that has been entrapped in the voids of sedimentary or extrusive igneous rocks at the time of deposition Consistency: The relative ease with which soil can be deformed Consolidation: The gradual reduction in the volume of a soil mass resulting from an increase in compressive stress Consolidation Test: A test in which a soil sample is laterally confined within a ring and then compressed between two porous plates; the vertical movement (consolidation) is recorded by a vertical deflection dial at given time intervals.

protect core samples during transport or storage. A core box contains core samples placed horizontally in parallel slots, with sample numbers and depth increments inscribed on the box or core samples Core Recovery: The ratio of the length of the core recovered (useable sample) to the length of the attempted core recovery Core Sample: A cylindrical sample of rock or soil recovered from a borehole Core Sampling: The process of cutting a core sample by use of an annular (hollow) drill bit Creep: (1) The slow downhill movement of rock, soil, or debris, usually imperceptible except during long term monitoring; (2) person in a position of power who directs contractors, inspectors, or other personnel to perform untoward or unethical construction related operations Critical Failure Path: The path along which failure will generally occur; the path that has the lower ratio of shearing resistance to shearing stress Critical Slope: The maximum angle with the horizontal surface at which a sloped bank of soil or rock of a given height will stand unsupported

Contour: A line indicating elevation on a topographic map or grading plan

Cryology: Study of the properties of snow, ice, and frozen ground

Core Barrel: A length of tube, typically 10 ft in length, designed to receive a core sample as it is being drilled by the bit; the core barrel then retains the core sample during its removal from the borehole.

Cure Time: The interval of time between adding cementitious ingredients and the substantial development of strength

Core Box: A lidded wood, metal, or cardboard container designed to

Curtain Grouting: The subsurface injection of grout in a manner that will create a barrier to occlude the anticipated flow of water

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Curve: Slang term for the laboratory Maximum Density Test Cut (removal): (1) The act of excavating a material; (2) the depth to which a material is to be excavated Cutoff Wall: A subsurface vertical barrier created by excavating a trench of specified width and depth, and then filling it with a material of low permeability (such as bentonite); used to contain or block the flow of water or other fluids Cuttings: Rock chips and fragments produced while coring or drilling into rock Daily Field Report (DFR): A daily written record produced by an inspector or technician that documents observations, testing performed, meetings held, construction work completed by the contractor, and other information relevant to the construction process Datum: A survey reference location— indicating a specific point and elevation—used as a starting point for subsequent measurements Daylight Line: (1) The contact between cut soil and fill soil as produced during the grading of a site; (2) the boundary line of either the cut or fill where they meet the natural ground (the light of day)

Debris Flow: The rapid downslope plastic, mud-like flow of a mass of earthen material Deflocculating Agent: See Dispersing Solution. Deformation: A change in shape or size Degree of Compaction: See Percent Compaction. Degree of Consolidation (Percent of Consolidation): Ratio expressed as a percentage of the amount of consolidation at a given time within a soil mass to the total amount of consolidation obtainable under a given stress condition Delta: A low, nearly flat land at or near a river’s mouth, consisting of alluvial deposits Density (Unit Weight): The weight or mass of material per unit volume Density Test (Field Density Test, Compaction Test) (Chapter 4): A field test used to determine the inplace unit weight of a soil formation, compacted fill, or other material; examples are sand cone and nuclear density tests. Desert Varnish: A dark, shiny deposit of manganese and iron oxide that covers many exposed rock surfaces in the desert

Daylighted Plane: The point at which a bedding or shear plane intersects on a slope face, thus meeting the light of day

Desiccated Soil: Expansive soils (usually clayey) that have cracked because of shrinkage from drying

Deadman: A buried plate, wall, block, or other anchoring device that is tied to a retaining wall to keep the wall from failing; a deadman is held in place by its own weight.

Diatomaceous Soil: A mixture of soil and fossil skeletons of microscopic plants, typically has a low unit weight and high optimum moisture content

Appendix C: Glossary of Geotechnical Related Terms

Differential Settlement: Uneven settling or sinking of earth materials beneath a foundation (footing, slab, etc.)—which may be indicated by cracking or uneven vertical displacement—caused by uneven support (differential support) Dike: A thin layer of igneous rock, resulting from hot magma being forced into a vertical crack or joint and then cooling in place Dilatancy (Shaking Test) (Chapter 1): The increase in volume (density) of saturated silt—which when wetted— silt particles become denser upon shaking or jarring (i.e., water is displaced from between the silt particles); more tightly bound clay particles do not change in density when jarred Dip: The angle between the plane of bedding and the horizontal plane Direct Shear Test: A test in which soil, under an applied load, is stressed to failure by moving one section of a container (shear box) transverse to the other section (see ASTM D 3080) Dirty Soil: Soil with a large percentage of clay or silt (fines) intermixed Dispersing Solution (Deflocculating Agent): A liquid mixture that prevents fine soil particles in suspension from coalescing to form flocs Double Dumping: The placement (by scraper or other equipment) of two or more consecutive lifts of material prior to the proper compaction and processing of the initial, lower lift Dozer: Slang term for bulldozer Drag Bit: A rigid steel drill bit that is used to drill into soft to medium hard

soil and rock formations; often used in clayey soils Drawdown: The vertical distance that the free water elevation is lowered by the removal of the free water Drill Mud (Mud): Water mixed with clay (usually bentonite) or other materials such as oil or barite; used as a circulating fluid to help cool the drill bit, stabilize the borehole walls, and bring the cuttings to the surface Drive Sampler (Chapter 2): A thickwalled steel tube composed of a drive shoe (at the tip), a sample barrel (which may or may not contain rings), and a waste barrel (at the top); the drive sampler is forced into the soil by hydraulic pressure or percussion by a drive hammer. Dry Pack: A cement and sand mixture with low water content; used to fill cracks, small holes, and imperfections in poured concrete Dynamic Compaction: The densification of fill by applying impacting loads Earthen Material: Rock or natural soil Effective Diameter (Effective Size): The particle-size diameter that corresponds with the point at the 10% finer plot on a grain-size curve EIT (Engineer in Training): A professional designation given by a state government that confirms that the person has met educational and exam requirements including the Fundamentals in Engineering test (FE exam). The EIT designation is an intermediate step to becoming a licensed professional engineer (P.E.).

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Elastic Limit: The maximum stress that can be applied to a material mass without causing its permanent deformation; in the case of a fault or a fold, the elastic limit has been exceeded and the deformation has become permanent.

Existing Grade (EG, or Original Grade, OG): Indicates the elevation of the existing or natural ground surface prior to any grading process

Elasticity: The property of a soil that, after being deformed, causes it to return to its original shape and size when the deforming forces are removed

Expansive Soil: A soil (usually of clayey character) that increases in volume (expands) with added moisture and decreases in volume (shrinks) when the moisture content is reduced

Electrokinetics: The application of an electric field to a soil zone to dewater materials of very low permeability to enhance stability Elevation: The height above a fixed reference point (such as city or county datum, or “Mean Sea Level”); elevation is used in all stages of construction and is determined by direct measurement and surveying Engineered Fill: Earthen materials that have been placed mechanically under controlled conditions and documented in accordance with specific engineering standards or recommendations

Exothermic: Refers to a reaction that produces heat

Face: The exposed portion of a slope, or a nearly vertical rock exposure False Cut: (1) A temporary slope excavation; (2) a preliminary back-cut in a slope to allow equipment or construction personnel to safely work Fault: A fracture in the Earth’s crust across which there has been relative movement Fault Gouge: A layer of clayey material that develops between the slip planes of a fault, resulting from movement across the fault Field Density Test: See Density Test.

Engineering Geology: The use of geologic experience and principles to define and control geologic hazards during the construction of engineered earthwork projects

Fill/Artificial Fill (AF): Earthen material, debris, or other matter placed by human forces

Eolian Deposits (Aeolian): Unconsolidated sedimentary formations— primarily composed of sand or silt—developed by the wearing away of the earth surface and transported by actions of wind

Filter (Permeable): A layer or combination of layers of permeable material, typically sand or gravel, sometimes overlaid or enveloped by fabric; designed and placed in such a manner as to allow for drainage yet limit the migration of fine soil particles

Excavatability: See Rippability. Excavation: The mechanical removal of earth material

Filter Fabric: A nonwoven fabric used to allow the flow of water while limiting the migration of fine soils.

Appendix C: Glossary of Geotechnical Related Terms

Fabric type (opening size) may be adjusted depending on the soil strata of placement. Woven fabrics may also have filtering properties, as well as giving more strength than non-woven fabrics. Fines: The portion of soil finer than the No. 200 sieve (75 μm), which includes silt, clay, and colloid particles Finish Grade (FG): The final ground elevation upon completion of the grading process per approved plans Finished Subgrade (FSG): The final surface elevation of a roadway, parking lot, or other surface to be paved or traveled on—just prior to the placement of subbase or aggregate base material

Foliation: A characteristic of metamorphosed rocks in which minerals are aligned in one direction, allowing the rock to be easily split into thin layers Footing (Foundation): Lower portion of a structure that transmits the load directly to the Earth Formation: A similar structure or geologic arrangement of a soil or rock mass in a certain region or area Fracture: A crack or break in a body of rock causing a discontinuity, such as a joint or fault Free Water: Water that is free to move through a soil or mass under the influence of gravity Friable: Easily broken or crumbled

Fissure: A long, narrow fracture in rock Floating Slab: A slab that is laying over the ground without any anchoring; may be post-tensioned Floc: Loose, open structured mass formed in a suspension by the aggregation of minute particles Flow Failure: A failed zone of soil that has moved over a relatively long distance in a fluid like manner Flowline: The level or elevation that water will flow at in a utility trench, ditch, or other drainage course Fly Ash: A fine glassy mineral residue resulting from the combustion of coal in electric generating plants; often used as a replacement for Portland cement in concrete Fold: A bend in rock strata or a layer

Frost Heave: The rise of ground surface resulting from an accumulation of ice crystals in the material below Gabion Basket: Wire basket filled with rock (which can be premade or built on site); used for waterway, stream bank, and hillside erosion protection Geogrid: A synthetic grid—typically composed of woven or welded yarns that are often coated with polymers, PVC, or other synthetics; may be of uniaxial or biaxial design, depending on intended usage (e.g., for roadways, slopes, or retaining walls) See Stabilization Fabric. Geologic Hazard: A geologic feature that is unstable or dangerous; can be a natural phenomenon or anthropogenic in origin

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Geologic Map: A map showing the distribution of soil and bedrock formations, including folds, faults, and mineral deposits—each designated by an appropriate symbol

Glacial Till: Material placed by glaciation, usually composed of a wide range of particle sizes, that has not been subjected to the sorting actions of water

Geology: (1) The science of the Earth’s history, soil, rocks, and physical changes; (2) the features or processes occurring on land in any given region on earth or on a celestial body

Grade: (1) The preparation of the ground by cutting or filling (grading) according to a predetermined plan; (2) the vertical location of the ground

Geophone: An electronic instrument that can detect vibrations from within the Earth Geophysical Exploration: The exploration of subsurface conditions to determine the distribution of certain physical properties within rocks, such as specific gravity, electric conductivity, magnetic susceptibility, elasticity, and seismic characteristics Geotechnical: Pertaining to the practical applications of soil science and civil engineering Geotechnical Engineer: See Soil Engineer. Geotechnical Technician: See Soil Technician. Geotextile (Geofabric): A permeable fabric used during grading to stabilize, allow for drainage or filtration, or add reinforcement beneath an engineered structure GIT (Geologist in Training): A GIT is a professional designation required in some states. It is a recognition the person has passed the Fundamentals in Geology test (FE exam) and has met specific educational requirements. The GIT designation is an intermediate step towards becoming a licensed professional geologist (P.G.).

Grade Beam: A horizontal part of a foundation system that transfers vertical loads to individual foundation elements or gives lateral support to vertical members; a grade beam is typically cast on the surface. Grade Break: Indicates a change in slope inclination or vertical elevation Grade Checker: A person on a grading project who helps to ensure that the grading of the site conforms to the contours on the grading plan; the grade checker reads and places new grade stakes, checks elevations by use of survey equipment, GPS, or a simple peep sight (hand level), and often directs the equipment operators in the amount of cut or fill necessary. Grade Stake: A piece of wooden lath onto which elevations and other information related to the grading of a project is written Grading: The act of moving earthen material during the construction process Grading Plan: An engineered design that may be viewed on paper or computer; indicates the existing ground surface and the final contours of which are used during grading an earthwork project Grain Size Analysis (Gradation or Sieve Analysis): The process of

Appendix C: Glossary of Geotechnical Related Terms

determining gradation, typically performed by passing material through various size screens or sieves (see ASTM D2487) Granular: Soil constituents larger in diameter than the No. 200 (75 μm) sieve: sand and gravel Gravel: Particles of rock that will pass the 3 in. (75.00 mm) sieve and are retained on the No. 4 (4.75 mm) sieve: between sand and cobble size Grizzly: A large heavy-duty screen used on grading projects for separating rocks from soil. Grizzly screens may be made with openings of any size— depending on the project needs—to separate out gravel, cobble, or larger size rock Groundwater: Water that is present below the water table within the zone of saturation Grout: A pumpable or spreadable mixture of chemicals or of cement and fine sand; commonly pumped into a borehole or injected into a fracture to help seal and/ or stabilize the ground Grouting: The act of pumping a slurry of cement or a mixture of cement and fine sand or chemicals into crevices, voids in a rock, or a soil formation to prevent groundwater from seeping into an excavation or to increase the bearing value and/or raise the ground level beneath a foundation Grubbing: The process of clearing and removing brush, vegetation, and trees from a project site in preparation for grading Gunite: A dry mix process in which cement and sand are placed into a

hopper, then pneumatically conveyed through a hose to a nozzle, at which point an adjustable amount of water can be added as the mix is being sprayed onto the receiving structure; gunite is highly heat resistant and bonds well to surfaces such as concrete, brick, tile, stone, and steel. Gypsiferous: A soil mass that contains an appreciable amount of the mineral gypsum Gypsum: Hydrous calcium sulfate evaporate mineral, generally white to clear, crystalline to massive, with a hardness of 1½ to 2 on the Mohs scale for hardness Half Life: The average time required for a radioactive element to decay to half of its original value Hand Level (Peep Site): A surveying instrument used for quick determination of elevations. It is typically used by “grade checkers” and technicians on grading projects Hand Probe: See Probe. Hardness Scale (Mohs Scale): An important mineral identification test in which the hardness of minerals is ranked numerically from the softest (1) to the hardest (10). Each mineral of higher numeric value is capable of scratching any mineral below it on the scale. This was devised by the German mineralogist Frederick Mohs. The hardness scale is represented by the following 10 minerals: 1–talc, 2–gypsum, 3–calcite, 4–fluorite, 5–apatite, 6–orthoclase, 7–quartz, 8–topaz, 9–corundum, and 10–diamond. Hardpan: A hard, relatively impermeable and insoluble cemented layer of soil or rock

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Haul Road: A temporary access road for heavy equipment to travel on during the grading process Heave: An upward movement of soil caused by expansion or displacement as a result of frost action, water increase, removal of overburden, loading of an adjacent area, or even the driving of piles Heavy Equipment: Dozers, blades, excavators, drill rigs, scrapers, large trucks, and so forth Homogeneous Material: A mass of material that exhibits the same properties throughout Horizon (Soil Horizon): One layer of a soil profile, distinguished from adjoining layers by texture, color, mineral content, or structure Hub: Surveying stake from the top of which elevations and distances are measured and computed Humus: A dark brown or black highly organic soil formed by the decomposition of vegetable or animal matter Hydro Seeding: A method of applying grass seed or other seed mixtures —typically blended with wood fiber and fertilizer—onto a surface, with water forcing the blend through a hose and nozzle; hydro seeding is often used immediately after the grading process (or before the rainy season) to help stabilize slopes and surficial sediments Hydrology: The scientific study of the Earth’s water, including its properties, movement, abundance, usage, chemistry, and distribution

Hydrometer: A sealed hollow glass buoyant instrument, with mercury filled in the wider bottom for stability; the thinner top stem is calibrated and graduated for reading measurements (readings taken at the top of the meniscus along the stem). The hydrometer readings depend on particles in suspension (changing with liquid density and viscosity); temperature and other test variables will influence readings. Hydrometer readings may be calculated (using Stokes’ Law) to determine the percentage of fines (silt, clay, and colloids) in the solution being tested. Hydrometer Analysis: The determination of the grain-size distribution for particles smaller than 0.075 mm (No. 200 sieve) by the use of a hydrometer (refer to ASTM D 7928) Hydrostatic Head: The fluid pressure of water produced by the difference in elevation between a given point and the free water elevation Hydrostatic Pressure: The pressure of a liquid under conditions for which all of the principal stresses are equal; the fluid is considered at rest—static; for instance, a solid body immersed in a fluid (such as water) will have an upward buoyant force acting upon it equal to the weight of the displaced fluid, owing to the hydrostatic pressure in the fluid. Hygroscopic Water Content: The weight of water content remaining in an air-dried soil, whereas the hygroscopic coefficient is the percentage of water remaining in an air-dried soil Igneous Rock (Volcanic Rock): A rock that was formed by solidifying from a molten (melted) state (e.g., basalt, obsidian, and granite)

Appendix C: Glossary of Geotechnical Related Terms

Import Material: Fill material that has been acquired for use in grading or backfill from an off-site location In Situ (In Place): Refers to a soil or rock formation in a natural or undisturbed condition Inclination (Slope Angle): A description for the slope of a surface (such as a hillside), indicated by the ratio of horizontal to vertical distance; for instance, a 2:1 slope (26-degree angle) would indicate that for every 2 ft out (horizontal), a 1 ft drop (vertical) is necessary; a 1:1 slope would be a 45- degree angle, with 1 ft out and 1 ft down. International Building Code (IBC): A model building code developed by the International Code Council (ICC, formed in 1994) and since adopted throughout most of the United States. First published in 1997, the IBC has replaced the UBC. International Code Council (ICC): Established in 1994, a global membership association dedicated to model codes, standards, and building safety solutions. Some of the ICC’s services include educational programs, certification programs for inspectors, technical handbooks, and training information. Interstice (Intergranular space): The small space or void between rock or soil particles Invert: The lowest point (elevation) of an underground excavation such as a pipe flow line, a utility trench bottom, or a tunnel bottom Isotropic Mass/Isotropic Material: A material or mass whose properties do not vary with direction

Jetting: A method for settling predominantly granular, low-cohesive to non-cohesive soil; performed by injecting water into a soil mass (typically trench backfill material) by use of a specially designed pipe at many adjacent locations until the soil mass is thoroughly saturated and settled. Often a Sand Equivalency (SE) value of 32 or greater is used to help confirm jettable material. Joint: A fracture or break of geologic origin in a body of rock in which no appreciable movement has occurred parallel with the fracture Kaolinite: A gray to white clay composed of hydrous aluminum silicate Karst: A description for topography that includes sinkholes, caves, and underground streams that have been formed in limestone formations Kelly (Kelly Bar): On a drill rig, a square or fluted pipe that goes through and is turned by a rotary drill table yet is free to move up and down; the drill stem is attached to the bottom end of the Kelly. Key (Keyway, Base Key): A trench excavation made below the toe of a fill slope, buttress, or stabilization fill. The depth and width are usually determined by the height of the proposed fill, and the necessary material to be excavated into at the toe of the key. A key is typically excavated at a 2% gradient into the slope and then filled in with compacted material. It should act as a strong contact between the existing stable lower ground (at the toe of the fill) and the proposed fill slope. Keystone Wall: See Block Retaining Wall.

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Kicker (Kicker Block or Thrust Block): Cement poured against a bend or angle of an underground pipe (that is under pressure) for support Landfill: (1) A land area into which solid waste is placed; (2) an originally low area of land that has been built up and stabilized with earth, rock, concrete, and other approved construction products to create new land for development Landslide (Slide): The failure of a sloped bank in which the movement of the soil and/or rock mass has taken place along a slide plane Lath (Survey Stake): A stake of wood, typically 2 to 3.5 ft in length by 2 in. width, and about a 1/2 in. thick; used by surveyors and grade checkers to mark specific elevations and locations on a grading project Leaching: The removal of soluble material by percolating water Lens: A layer of ore, rock, or soil that is generally thicker in the middle and thinner at the edges LID (Low Impact Development): Refers to systems and practices that use or mimic natural processes that result in the infiltration, evapotranspiration, or filtering use of stormwater in order to protect water quality, aquifers, and aquatic habitat. LID is one of many strategies and techniques used to counteract the impact of covering natural ground surfaces with concrete, asphalt, commercial and private structures, or other human construction that occludes the natural surface infiltration of stormwater. LID features (such as bioswales, infiltration trenches, bio-retention basins,

pervious concrete, underground infiltration systems, and more) help to recharge the natural aquifers, as well as minimizing stormwater and polluted run-off from entering municipal storm water systems—thus protecting creeks, streams, rivers, freshwater reservoirs, and oceans. Lift: (1) A loosely spread layer of soil, asphalt, or other material as placed prior to compaction; (2) the thickness of a layer of soil, asphalt, or other material after completion of compaction. Thicknesses of the lifts to be placed are usually determined by the type of material, as well as the compaction equipment to be used, and are designated by geotechnical recommendations. Lime: (1) Calcium oxide (CaO2); (2) a general term for various forms of quicklime, hydrated lime, and other chemical variations of predominantly calcium oxide mixtures; has a high pH and is considered alkaline. Lime Stabilization (Limetreate): A method of soil treatment that uses quicklime (CaO) or hydrated lime (CaOH2)—typically 2% to 8% per dry density—blended into reactive soils (especially silica-rich clays) to increase the stability of soft/wet soils while decreasing the plasticity of clayey soils Liquefaction: The sudden extreme decrease of shearing resistance and collapse of structure—from shock or strain—causing the increase of pore fluid pressure in a non-cohesive soil; it involves the sudden and temporary transformation of a solid mass of material into a liquefied form. Liquid Limit: (1) Test: The water content at which a pat of soil, after being placed in a liquid limits’ device bowl, and having a groove of

Appendix C: Glossary of Geotechnical Related Terms

standard dimension cut through it, will then flow closed for a 13 mm (1/2 in.) length after 25 drops of the bowl (see ASTM D 4318); (2) the water content corresponding to the arbitrary limit between the liquid and plastic states of a soil. Lithology: The description of rocks in outcrops or hand specimens on the basis of characteristics such as color, structure, mineralogy, and particle size Live Load: The load imposed on a structure caused by temporary or occasional forces, such as wind, earthquakes, people, vehicles, or movable heavy objects Loam (Topsoil): Soil having a relatively even blend of sand, clay, and silt, as well as an appreciable amount of organic material Loess: Fine grained soil deposited by the wind Lost Circulation: A condition that occurs when drilling fluid (drill mud) escapes into cracks, crevices, or porous sidewalls of a borehole and does not return (circulate) to the top of the boring Low Impact Development: See LID. Magnitude: A measure of energy released by an earthquake Manometer: A measuring instrument that uses the rise and fall of a head of water to determine the elevation change of a surface from a known reference point Mantle: The layer of the Earth between the crust and the core Marl: A calcareous clay, usually consisting of 35% to 65% calcium carbonate (calcite)

Mass Movement (Mass Failure): The downhill creep, slip, or sliding of a unit of land Matrix Material: In a rock fill (in which more than 30% of the material is larger than 3/4 in. diameter), the predominant soil that is smaller than 3/4 in. diameter (that fills in the void space) is considered the “matrix material.” Maximum Density: The dry unit weight of a material as defined by the peak of a compaction curve (moisture-density relationship curve) Maximum Density Test (standard Proctor, modified Proctor, Curve, Max): A laboratory compaction procedure in which soil at a consistent moisture content is placed in a specific manner into a mold of given dimensions, subjected to a compactive effort of a controlled magnitude, with the resulting wet unit weight determined; the procedure is repeated at various moisture contents (points) to establish a relation between the moisture content and the dry unit weight, in the form of a compaction curve (refer to ASTM D 1557 or ASTM D 698). Metamorphic Rock: A rock that has formed from another rock (without melting) in response to changes in temperature, pressure, and chemical environment that has taken place generally well below the Earth’s surface; examples include quartzite from sandstone, gneiss from granite, and slate from shale. Micaceous: Used to describe a soil or rock type that contains an appreciable amount of mica—a relatively soft mineral (between 2 and 4 on Mohs hardness scale) distinguished by its thin, flexible, elastic flakes

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Migration: See Piping. Mineral: An inorganic substance occurring naturally, having a specific chemical composition and an identifying hardness, usually formed with a definite crystal structure. Minerals are constituents of rocks; a few mineral examples are quartz, mica, gold, and diamond. Modified Proctor (Maximum Density Test): A laboratory compaction test using a 10 lb hammer, 18 in. drop, with five layers compacted into a cylindrical mold (see ASTM D1557); it is currently the preferred maximum density test because it compares better with the heavier modern compaction equipment. The original standard Proctor (developed in 1933) uses a lighter hammer, shorter drop, and only three layers placed in the mold. Mohs Scale: See Hardness Scale. Moisture Barrier (Vapor Barrier): A layer of material placed beneath slabs or onto concrete, masonry, or soil walls to prevent the migration of water or fines. Waterproofing materials include (but are not limited to) visqueen (plastic), urethanes, asphalt emulsions, and clay-based products Moisture Content (Water Content): The ratio (expressed in a percentage) of the weight of water contained in the pore space (interstices) of a soil mass to the weight of the solid particles Montmorillonite: A clay that is formed of very small platy micaceous crystals and swells to many times its size with the addition of water

Mud: (1) A mixture of soil and water in a fluid to semisolid state; (2) slang for drill mud or concrete Mudflow: A moving mixture of soil, rock, and water with the consistency of mud Mud jacking – The forcing of a cementitious mixture under pressure into a soft zone beneath a structure to either raise or add support to the foundation Munsell Soil Color Chart: A soil color classification chart based on a system devised by Albert Munsell and accepted by the scientific industry in the early 1900s; Munsell defined color in terms of hue, value, and chroma, giving each color chip a specific color name and alphanumeric designation, such as “dark yellowish brown, 10 YR 4/2.” Mylonite: A microscopic breccia with flow-type structure formed in fault zones Natural Ground (NG): (1) Soil and rock that have been deposited by the forces of nature through weathering, erosion, etc., soils that have not been moved by humans; (2) the undisturbed surface prior to the commencement of a grading project— sometimes referred to as original ground (OG) Nesting: (1) The grouped placement of gravelly or rocky material in a manner that leaves voids between the piled (nested) boulder, rock, or gravel fragments that are not infilled with compacted material (matrix material); the absence of nesting in a “rock fill” is required; (2) occurs when the fines and sand (matrix material)

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become separated from the gravel portion of the aggregate base—when an aggregate baserock (AB) may have been driven on by vehicles, or over-worked with a blade, causing it to become segregated or nested NICET (National Institute for Certification in Engineering Technologies): Founded in 1961, NICET provides universally recognized certification for individuals in engineering technology and a multitude of other disciplines. N Value: The penetration resistance (N) is measured by counting the number of blows (30 in. drops), it takes a 140 lb hammer to drive a split barrel sampler 1 ft. This is the Standard Penetration Test (SPT). From this blow count, the relative consistency or density of a soil (N value) can be determined (Table C-1). Non-cohesive: See Cohesionless Soil

Non-woven Fabric.

Fabric:

See

Filter

Nuclear Gauge: An instrument used to determine the in place degree of moisture and compaction, as well as the wet or dry density of a material; a nuclear gauge uses radioactive material in the determination process, typically cesium-137 for density determination and americium-241/beryllium for moisture calculation (refer to ASTM D 6938) Occlude: To block, prevent, or cut off the flow or passage of water Open Cut: An excavation made through a soil or rock layer (typically a hillside) that leaves a slope on each side of the cut—created to facilitate the passage of a roadway, railroad, or waterway Optimum Moisture: The moisture content at which the maximum dry

TABLE C-1 N value for the Standard Penetration Test (SPT) Relative Density for Coarse-Grained Soil

Relative Consistency for Fine-Grained Soil

Penetration Resistance in blows/ft (N)

Relative Density

Penetration Resistance in blows/ft (N)

Relative Consistency

0–4

Very Loose

30

Hard

>50

Note: Coarse-grained soils are predominantly sands, and fine-grained soils are predominantly silts and clays.

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density of a soil can be achieved, indicated by the top point of a compaction curve; each soil type (or blend of soil types) has its own specific optimum moisture content that is used as a guide for moisture conditioning during the grading/ compaction process. Organic Soil (PT): Soil with a high content of plant or animal material, such as peat OSHA: Occupational Safety and Health Administration (federal) Outcrop (Outcropping): The portion of the bedrock that is exposed to view at the ground surface Overburden: (1) The loose uppermost soils; (2) earthen or waste material directly overlying the material of planned removal or concern Over-consolidated: A soil mass that has been subjected to a load greater than the existing overburden pressure

Packer: A device lowered into a borehole that automatically swells or can be controlled to expand at the correct time to produce a watertight seal against the sides of a borehole or casing Parent Material: Material from which a soil has been derived Particle: A general term referring to any individual size grain, from a microscopic colloid to a huge rock Pass: One trip or movement across a designated area by a piece of excavation or compaction equipment Pavement Section (Structural Section, Section): The combined thickness of asphalt, aggregate base, and sometimes aggregate subbase material that is designed and recommended by an engineer as a total roadway structure; the designed thickness of this pavement section is based on factors such as R value of subgrade soils, traffic volumes, and loads (Traffic Index, TI).

Over-excavation (Over-ex, OX): The removal of a soil or rock strata that is below the proposed finish grade elevation but must be replaced with compacted material that is acceptable to the planned project

Pea Gravel: Clean gravel with grain size of approximately 5 mm in diameter (No. 4 sieve)

Oversized Material: (1) Boulder or rock fragments that exceed the maximum diameter allowable in a soil or soil–rock fill as specified by the plans, specs, or geotechnical report; (2) material deemed untestable by the nuclear gauge and sand cone methods—because more than 30% of the material is larger than 3/4 in. size (by weight)—as limited by the maximum density test (both ASTM D 1557 and D 698 methods).

Pedology: The science that pertains to soil, including its nature, properties, formation, functioning behavior, and response to use and management

Peat (PT): A fibrous, highly organic soil, generally dark brown to black

Peep Site: See Hand Level. Penetration Resistance: See N Value. Penetrometer: Penetrometer.

See

Pocket

Appendix C: Glossary of Geotechnical Related Terms

Percent Compaction (Degree of Compaction): The ratio (expressed as a percentage) of the dry density of a soil (as determined by a field density test) to the laboratory maximum dry density (or wet density to wet density). Percent of Consolidation: See Degree of Consolidation. Percent Saturation: The ratio (expressed as a percentage) of the volume of water in a given soil mass to the total volume of the intergranular space (voids) Perched Water Table: A water table (usually of limited area) maintained above the normal free water elevation by the presence of an intervening, relatively impermeable confining strata Percolation: The movement of gravitational water through permeable soil Percussion Drilling: A drilling method that uses a solid or hollow-stem auger to cut and crush rock with repeated blows Perforated Pipe (Perforated Drainpipe): A plastic pipe (typically PVC) with two rows of holes (perforations) equally spaced along the bottom third of the pipe; proper placement of the pipe is with the holes facing downward—thus allowing water to flow up into the pipe, while minimizing the migration of fines (sediment) through the holes. Drainpipe is typically surrounded by drain rock, which is in turn enveloped with filter fabric. Permafrost: Perennially frozen soil or ground that remains below freezing temperature for two or more years

Permeability: The ease with which water will flow through soil or rock; for example, clean sand is a permeable soil, whereas highly plastic clay is impermeable. Permeability Test: A procedure often used to determine the infiltration, or water tightness of a soil or rock formation; it may be used prior to the construction of a dam, pond, or detention basin, or to help ascertain infiltration rate of an LID feature. The field test is performed by placing packer assemblies in a borehole to seal off successive strata or at specified intervals (typically every 5 ft). Water is injected into the borehole space between the packers with a high-pressure pump. The volume of water lost in each rock, soil formation, or interval is a measure of permeability. pH: The measure of acidity or alkalinity of a solution—or soil when dampened; the pH of pure water is 7 (considered neutral); the higher the number, the more alkaline (base) the solution; pH lower than 7 is acidic. Piezometer: An instrument for measuring pressure head Pile (Friction or Bearing): A structural element that is driven, drilled, or otherwise introduced vertically into the soil or rock formation for structural support; support is provided by skin friction between the pile and soil (friction) and/or by end bearing of the pile tip on the lower stratum. Piping (Migration): The progressive washing away (migration) of soil particles (generally fine sand, silt, or clay) within a mass caused by the percolation of water, leading to the development of channels and the potential settlement or collapse of the

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material mass, and the supported structure Pitcher Tube (similar to Shelby Tube): A thin-walled steel tube used to sample soil or soft rock from a borehole; Pitcher Tube sampling is done from drill rigs equipped with rotary wash tools. Plastic Limit (PL) (Chapter 3): (1) Test: The water content of a soil at which it will just begin to crumble when rolled into a 1/8 in. thread (see ASTM D 4318); (2) the water content corresponding to an arbitrary limit between the plastic and semisolid states of consistency of a soil Plasticity: The property of a soil that allows it to be deformed beyond the point of recovery without cracking or appreciable volume change Plasticity Index (PI) (Chapter 3): The numerical difference between the liquid limit and the plastic limit Plasticizer: A chemical additive that will increase the workable time (plasticity) of a cementitious mixture Pneumatic Tired Roller: A heavy roller with air filled rubber tires— typically used to compact cohesive soils and asphalt Pocket Penetrometer: A handheld piston-type device that when pushed into a soil (either in-place, or into a soil at the end of a sample tube) can give an indication of the cohesive soil strength and consistency—read from 0 to 4.5 in ton per sq. ft (tsf); the pocket pen can be used to evaluate the side walls of excavations per OSHA cohesive soil classification (see 29 CFR Part 1926, Subpart P – Excavations).

Pore Pressure: Stress transmitted by pore water (water within the voids of a soil) Porosity: (1) The ratio (expressed as a percentage) of the volume of voids in a given soil mass to the total volume of the soil mass; (2) indication of pore space or voids within a soil or rock mass Porous Soil: Soil with observable small voids, interstices, or holes; cohesive soils may appear “spongelike” because of holes from root decay, worm, or bug holes, etc. Noncohesive soils are considered porous because of void space between particles and/ or grains. Portland Cement: Cement that consists of the compound’s silica, lime, and alumina Portland Cement Association (PCA): Founded in 1916, PCA represents concrete companies in the United States and Canada. PCA conducts market development, performs engineering research, provides education, and employs code specialists who work in the field to promote and protect concrete interests in national building code organizations. Post-Tensioning: A method in which cables are placed into a slab area prior to pouring concrete, then, after the concrete has cured, the cables are tightened—stressing (or tensioning) the concrete—creating a slab that will move as a more monolithic unit (floating slab). Potato Dirt: A term used to describe earthen material that is easily worked (compacted or excavated) Pre-grade Meeting (Pre-con Meeting): An important meeting held

Appendix C: Glossary of Geotechnical Related Terms

prior to the beginning of the project detailing items such as estimated start and completion dates (schedule), specifications, plans, geotechnical recommendations, safety, and introduction of project personnel Pre-saturation: The moisture conditioning (above optimum moisture) of a pad and/or footing excavation prior to the pouring of concrete. Pre-saturation is usually performed on expansive soils to reduce future swelling of the soil (as may be caused by seasonal rains or heavy landscape watering), which may cause concrete foundations to heave, crack, or separate. Pressure Grouting (Mud Jacking): A method of stabilizing or improving the density of a soil mass by injecting under pressure (to infill voids) a mixture of cement, soil, and water Pressure Testing: A method to test the permeability of a soil or rock formation in which water or grout is pumped down a hole under pressure See Permeability Test. Pre-stressed Concrete: Concrete that has been compressed to reduce or eliminate cracking or tensile forces Probe (Soil Probe, Hand Probe): A “T” shaped implement (approximately 3 ft in length) with a pointed end; used as a guide in checking backfill, footing bottoms, or other questionable backfill areas for density or consistency Proctor: Slang for maximum density test; originated from the original maximum density test method proposed by R. R. Proctor in 1933 Proof Roll: The use of heavy rubbertired equipment (such as a fully

loaded water truck) driven over a road subgrade or aggregate base to help determine the stability of the surface Pumping: May be observed as a rolling motion in soil placed or compacted in an over optimum condition (too wet); these pumping soil may— during the compaction process— become rutted or indented by rubber-tired equipment, usually leaving a bulging path in the soil parallel to the tire print. In a condition of widespread pumping, the soil surface may move in a slow wave-like action while compacting. Proof rolling is a good method in which to locate pumping soils. Quicksand: A specific mixture of silt and fine sand in which the bearing capacity of the mass has been greatly reduced due to its thorough saturation by water R Value (Resistance Value): A test value resulting from a soil test in a Hveem stabilometer in which a short cylindrical sample prepared by kneading compaction is subjected to an axial load; the resultant horizontal pressure is measured, and the strength is expressed in terms of a resistance value (R). The R value is used in pavement design to help determine the thickness of the pavement section. A higher R value indicates a generally more granular soil and a better rating for road subgrade material. Raveling: The loosening, falling, or breaking away of materials from a bank, slope face, or pavement. Rebar: A steel reinforcement bar. Typical bar sizes are No. 3 (.375 in.) through No. 18 (4.00 in.) diameters; common rebar size used in a house

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slab are No. 4 bar, typically spaced at 12 in. each way. Recovery (Percent Recovery): The amount of soil or rock sample obtained from a borehole by use of any soil sampling device; may be expressed as the ratio of the sample length recovered to the sample length attempted Refusal: Term used in exploratory drilling to describe the time when a drill bit cannot proceed any further, or the point at which a sampling barrel or tube cannot be driven (or pushed) any further without damaging the sampler Relative Density: The ratio of the difference of a soil: (1) in its loosest state to any given void ratio, or (2) between the void ratios in its loosest and densest states, such as from a laboratory or field density test Retaining Wall: A reinforced wall designed to resist the lateral pressure produced by a potentially unstable soil or rock mass Re-work: To recompact a portion of previously compacted, but unaccepted, fill Rippability (Excavatability): The ease or difficulty with which removals or cuts can be made in rock or cemented soils Rippers: Steel shanks (tooth shaped attachments) that are placed on the rear of heavy equipment—such as blades and dozers—to help loosen (rip) rocky or cemented formations Ripping (Scarifying): (1) The process in which bedrock or hard cemented materials are broken up by a single shank (ripper tooth) of a

dozer; (2) the act of scarifying the ground surface by the ripper teeth of a dozer or a blade in preparation for fill placement. Rip Rap (Riprap): Broken rock (primarily cobble to boulder size) placed to protect embankments, cut slopes, shorelines, etc., against erosion from running water or wave action; rip rap generally is angular and has a number of fractured faces, as well as having a high enough specific gravity to help hold the material into place during wave or flood action. Rock: Naturally formed solid mineral matter, occurring in large masses or fragments Rock Fill: (1) Rocks, cobbles, or boulders blended with a soil matrix during placement with ample amounts of water—in such a manner as to limit voids and nesting, allowing for a homogeneous, well compacted fill; (2) a rock fill may be defined when more than 30% of the material is larger than 3/4 in. size (by weight), therefore un-testable with a sandcone or nuclear gauge according to the ASTM D1557 standard test method Rock Mechanics: (1) The theoretical and applied science of the mechanical behavior of rock, and the application of engineering practices in dealing with rock problems; (2) people who are experienced and specialize in the repair of broken rocks Rockery Wall: A retaining wall composed of angular, durable, dense rocks placed according to engineered design—typically inclined into slope (batter) of 1:6, with a fabric-encased rock drain placed along the back of the wall

Appendix C: Glossary of Geotechnical Related Terms

Roller Compacted Concrete (RCC): Cement and soil, usually mixed on site or nearby, placed and compacted in a near optimum/low slump condition Rotary Wash Drilling: A drilling rig using rotary tools and any type of circulating fluid, such as drilling mud (water and bentonite mixture), which helps to cool the drill stem/bit, as well as keep the hole from caving Rough Grade: The elevation to which a site is graded before “blue tops” are placed, typically within a few tenths or less of finish grade elevation Rough Grading: The early stages of a grading project when streets, pads, parking areas, etc., are graded to within a few tenths of a foot to finish grade Rupture Plane: Plane or surface in which failure or substantial movement has occurred Sample Grabber (Sample Catcher): A device that is placed inside a drive sampler between the drive shoe and sample barrel—used to help hold a non-cohesive soil in the sampler during sample recovery Sand: Particles of rock ranging in diameter between the #4 sieve (4.75 mm) and the No. 200 sieve (0.075 mm); as a unit, the sand grains are generally non-cohesive and permeable. Sand is between gravel and silt size. Sand Boil: The upward movement (ejection) of sand and water caused by piping Sand Cone: A device used to determine in place density of soil. The sand

cone is composed of three main parts: the cone is funnel shaped with a valve attached to control the flow of sand; the jar is a plastic (or glass) container to hold sand (screws onto the cone); and the plate is the guide for digging and seating the cone over the hole (refer to ASTM D 1556). Sandstone: A sedimentary rock composed of cemented sand grains Scarify (Rip): The act of loosening the existing surface material (usually by ripper teeth on a dozer or blade) to mix, blend, or prepare for fill placement Scarp: A steep, near vertical slope along the top or edge of a plateau, mesa, terrace, bench, landslide, slump, or fault Scraper: A large mobile truck-type transport—used for the hauling and transporting of earthen loads—that has a movable cutting edge and is able to discharge its load by sliding a movable wall within its bed Sedimentary Rock: A rock formed by the accumulation of mineral grains and rock fragments by erosion processes; may be cemented by agents such as silica, carbonates, or oxides Seepage: The slow movement of gravitational water through soil or soft rock Segregation: The separation of coarse and fine material, typically resulting from actions of water or motion. Seismic Refraction Survey: A method involves the transmission of seismic waves through rock and soil strata to help determine the hardness

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(excavatability/rippability) of an area of proposed cut Seismic Wave: A wave generated by an earthquake, explosion, or a hard impact that travels through the Earth; seismic waves may vary in velocity depending on the intensity of the source and the strata through which they are traveling. Shaking Test: A method used to determine the dilatancy of a soil Shale: A sedimentary rock composed primarily of silt and clay; it tends to break and fracture in thin layers. Shear Failure: The parallel adverse movement along a plane of contact within a soil mass—of sufficient magnitude to seriously damage or destroy the structure of the mass

Shoring: Wooden or metal braces placed against the side walls of a trench or other excavations for safety; used to help prevent the walls from sloughing or caving in Shotcrete: A prepared wet mixture of concrete that is pumped through a hose to a nozzle, at which time compressed air is introduced to impel the mixture onto the receiving structure. Shotcrete has a high heat resistance and adheres well to concrete, brick, tile, stone, and steel. Shotcrete may be sprayed over reinforced soil surfaces to help retain slopes or vertical cuts. Sieve: A wire (or nylon) mesh with specific size openings used to separate soil grain sizes. Sieve Analysis: See Grain Size Analysis.

Shear Key: A large trench (keyway) excavated through a creep, slide, or potentially unstable hillside to buttress the disturbed zones—but not placed at the disturbance base—then backfilled with compacted material to prevent sliding at the point of extra fill load

Silt: Material that is smaller than sand (No. 200 sieve, 75 μm) but has a particle diameter larger than clay (5 μm); silt will plot below the “A” Line on the Plasticity Chart, as defined by the liquid and plastic limits test.

Shear Strength: The maximum resistance of soil to shear stress

Siltation: The process by which silt, clay, and fine sand that is transported by rivers and streams is deposited along the way

Shear Stress: The action resulting from applied forces that tends to cause soil masses to slide adversely in a direction parallel to their plane of contact

Site: Any parcel of land in which grading or construction is planned or performed

Sheepsfoot Roller: A steel drum roller with pads (feet) welded to its surface, used to compact soil Shelby Tube (similar to Pitcher Tube): A thin-walled steel tube used for sampling soil or soft rock

Skin Friction: The frictional resistance developed at points of contact between soil or rock and a structure Slab Foundation: A concrete foundation—which may or may not be supported by footings—that has been poured directly onto a prepared

Appendix C: Glossary of Geotechnical Related Terms

surface, with no crawl space or basement beneath it Slaking: The act of breaking apart or sloughing off when a hardened soil has been immersed in water Slickensided: A secondary structural feature in bedrock produced by movements along the walls of joints; slick and glossy in appearance Slide: See Landslide. Slide Plane: A plane of shear failure, roughly parallel to the slope face. Slope: An inclined ground surface; the inclination can be expressed as the horizontal distance to the vertical distance; for example, 2 ft horizontal to 1 ft vertical may be expressed as a 2:1 slope.

(stiffness) of freshly batched/poured concrete. The slump is a general indicator of the amount of water added to the mix and/or the time since the concrete was batched. Slump Test: A measurement of the workability (stiffness) of freshly batched concrete performed by placing the concrete mix (in three layers) into a metal cone (with the small opening upward), rodding each layer 25 times, then slowly removing the cone and measuring the amount of lowering (slump) of the material—as measured from the top of the cone to the top of the remaining material (see ASTM C143) Soil: Sediments and other accumulations of solid particles produced by chemical and physical disintegration of rocks; may or may not contain organic matter

See Inclination. Slope Angle: See Inclination. Slope Stability: (1) The resistance of a slope to mass failure; (2) to buttress, brace, or protect a slope in such a manner as to stabilize it from massive or partial failure Slope Wash: Soil and rock transported downhill by the actions of water and gravity Sloughing: The raveling or breaking off of material from any sloped or vertical face Slump: (1) A downward movement or slipping of a mass of earth material, characterized by a rotational motion, often recognized by a scarp at the top point of slipping and a bulge toward the bottom of the movement; (2) a measurement (performed by a slump test) of the workability

Soil Engineer (Geotechnical Engineer): An engineer experienced in the practical applications of soil science and civil engineering Soil Horizon: One of the layers of the soil profile, distinguished principally by its texture, color, structure, and chemical and mineral composition Soil Nailing: A method of reinforcing a potentially unstable soil or rock mass by inserting steel rods into predrilled holes, then grouting the rods into place, thus creating a more stable and solid monolithic mass Soil Profile: A vertical section of a soil mass showing the geologic nature (and often engineering properties) of various layers Soil Stabilization: A chemical or mechanical treatment designed to increase or maintain the stability of a

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soil mass or otherwise improve its engineering properties Soil Technician (Geotechnical Technician): A person trained to test, observe, and document the process of soil manipulation for construction purposes Soil Technology: The application of soil engineering and geology for the use of controlling and predicting the action of soil and rock for structural purposes Soil Technology, A Technician’s Guidebook: Published in 1981 and authored by Tim Davis Specific Gravity (of Solids): The ratio of the weight in air of a given volume of solids at a known temperature to the weight in air of an equal volume of distilled water at a known temperature Split Spoon: Slang for split barrel or SPT sampler Splash Block: A block of concrete placed beneath a downspout (drain outlet)—used to control erosion by allowing the water to discharge onto the concrete block, not the ground Spoil: Material that is excess or unwanted, typically disposed of off-site Spread: A term used by a grading contractor to describe the total heavy equipment (dozers, blades, scrapers, etc.) that will be or is being used on a grading project Spring: A location at the ground surface in which water seeps out more or less continually from the water table SPT: See Standard Penetration Test.

Stabilization Fabric: A geogrid or woven geotextile fabric that, when placed in a specific configuration (and usually overlain by a predominantly gravel mixture), will act as a stabilizing blanket over unstable soils such as peat, marshland, soft saturated clays, or pumping soils Stabilization Fill: An engineered fill placed to support or protect a natural slope against massive failure or the forces of erosion Standard Penetration Test (SPT): A down hole sampling method used in determining the relative consistency or density of a soil formation by obtaining a penetration resistance value (N value). The procedure is performed by lowering a split barrel sampler into a borehole, and then counting the number of 30 in. drops it takes a free falling 140 lb weight (hammer) to drive the sampler a depth of 1/8 in. Standard Proctor: The standard Proctor was proposed in 1933 by R. R. Proctor and was used as the standard maximum density test (ASTM D698) until being updated by the modified Proctor (ASTM D1557). In the standard Proctor test a 5.5 lb hammer with a 12 in. drop and three layers is used; the modified Proctor uses a heavier (10 lb) hammer, a longer drop (18 in.), and five equal layers placed in either a 4 in. or 6 in. diameter mold. Static Compaction: The densification of a soil mass by loading it with weight only, not by impact or vibration Sticky Limit: The lowest moisture content at which a soil will stick to a metal blade drawn across the soil sample

Appendix C: Glossary of Geotechnical Related Terms

Stockpile: A quantity of material temporarily placed in a secluded or remote location until the pile can be removed for intended use Stone: A small piece of rock of any shape, from gravel to cobble size Strain: The change in length, per unit length, in a given direction Stratification: (1) A parallel structure resulting from the deposition of sediment beds, layers, or strata; (2) the arrangement of rocks in beds, layers, and strata Stratum (Strata): A single layer of homogeneous or gradational lithology deposited parallel to the original dip of the formation; it is separated from adjacent strata or cross strata by surfaces of erosion, nondeposition, or abrupt changes in character. Stress: The force per unit area acting within the soil mass Strike: The geologic direction of a line created by a plane where it intersects the horizontal Subbase: A layer of material used in a pavement system between the subgrade and basecourse material Subdrain: A drainage system placed beneath the surface to drain subsurface water; it typically consists of filter material and/or a specified type and size of drain pipe. Subgrade: The layer of soil that is compacted immediately beneath the subbase or aggregate basecourse in a roadway section Subgrade Surface: See Finished Subgrade.

Subsidence: The sinking or lowering of a part of the Earth’s surface Subsoil: Soil below a subgrade or existing fill Surcharge: (1) A load behind a wall or structure that is applying a force or load against that structure; (2) a load applied to a soil in the laboratory or in the field, and then monitored for consolidation or settlement Surficial: (1) The unmoved surface of the Earth; (2) upper, near surface material. Survey Stake: See Lath. Swale: A depression in generally level ground; a swale may be developed by natural runoff water or may have anthropogenic origin, such as a drainage used to collect runoff and direct it away from buildings or other structures. Swell: An increase in volume resulting from the absorption of water into the intergranular pore space; many types of clay have a tendency to swell when wet. SWPPP (Storm Water Pollution Prevention Plan): A plan to help limit the runoff and uncontrolled drainage of storm water, sediments, and other pollutants that may result from construction activities; an SWPPP plan for construction projects must be developed in compliance with the Environmental Protection Agency (EPA) requirements contained in the National Pollution Discharge Elimination System (NPDES) as enacted in the Clean Water Act (CWA) and requirements of other governing agencies.

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Tailings: (1) Material that has been dropped, spread, or inadvertently placed without the benefit of adequate moisture conditioning or compaction—often remnant material from haul roads; (2) the waste material remaining after ore has been processed in a mining operation

Topsoil: Surface soil, usually containing organic matter

Talus: Angular rock debris accumulated at the toe of a slope or base of a cliff, produced by the action of weathering

Traffic Index (TI): An index of the expected level of traffic loading on a street or highway

Tamping: The act of compacting soil by use of weighted tools or machinery Tensile Strength: The load per unit area at which an elongated or cylindrical specimen will fail in a pull (tension) test Terrace: A relatively level step constructed in the face of a slope, used for maintenance purposes or drainage Thermo-osmosis: The process by which water is caused to flow through the interstices of a soil mass owing to differences in temperature within the mass

Track Walk: A process in which generally shallow compaction is achieved by track mounted equipment (typically a dozer) by repeatedly passing over an area of fill

Transition Lot: (1) A lot in which a portion is to be cut (or excavated) and a portion is to be filled (or raised) to reach finished pad grade; (2) a lot in which a daylight line passes through Tremie: (1) A hose or metal pipe of variable length used to pour concrete under water; (2) to place concrete through a pipe in a manner such that the concrete reaches the pour zone without mixing with water or segregating due to extensive free fall Trench Log: A written record of subsurface conditions observed during the excavation of an exploratory trench, including descriptions of soil, rock, strata, moisture, and orientation of the trench

Thrust Block: See Kicker.

Toe: The point at which the bottom of a natural, fill, or cut slope contacts with a relatively level or horizontal ground surface

Triaxial Strength Test: A laboratory test in which a saturated cylindrical sample of soil is encased in an impervious membrane, then subjected to a confining pressure and cyclic stress and loaded axially to failure; often used to simulate undrained field conditions that may arise during earthquakes or other cyclic loading (see ASTM D 5311)

Topography: The surface physical features of the land—its relief and contours

Unconfined Compressive Strength: The load per unit area at which an unconfined cylindrical sample will fail

Tie-backs: Engineer-designed—drilled and often grouted into place—anchors that are fastened into bedrock or soil

Appendix C: Glossary of Geotechnical Related Terms

in a simple compression test (refer to ASTM D 7012) Unconformity: A lack of continuity between two units of rock in contact, indicating an apparent gap in geologic record, the gap being a period of erosion

Unit Weight of Water: The weight per unit volume of water—normally equal to 62.4 lb/ft3 or 1 g/cm3 Uplift: (1) The hydrostatic force of water exerted on or underneath a structure, tending to cause displacement of the structure; (2) the upward movement of the Earth’s crust.

Under Consolidated Soil Deposit: A deposit that has not been fully consolidated under the existing overburden pressure

Utility Trench: A trench excavated for the placement of utilities, such as electrical, sewer, and gas

Underpinning: A footing introduced beneath an existing footing, for the purpose of transferring the foundation load to a lower depth onto more suitable material

V-Ditch: A V-shaped trench dug into the ground to collect and transport water, often placed along a roadway, across a bench in a slope, or tied into a low area to allow it to drain

Undisturbed Sample (Relatively Undisturbed Sample): A soil or rock sample that has been obtained by methods in which every precaution has been taken to recover the sample in its natural or in situ state

Vane Shear Test: An in-place shear test used in cohesive soils in which a rod with thin radial vanes at the end is forced into the soil and then rotated; the resistance to rotation of the rod is then measured—giving an approximate shear strength value

Unified Soil Classification System (USCS): A widely used system for identifying and classifying soil for engineering purposes, the system was developed by Dr. Arthur Casagrande in the early 1940s, and then was adopted for use by the US Army Corps of Engineers in 1952. It has since been standardized by ASTM and others.

Vapor Barrier: See Moisture Barrier.

Uniform Building Code (UBC): Standard specifications for safe construction, the UBC was published in book form and updated every four years The UBC was discontinued with the 1997 edition. The International Building Code (IBC) is now published as the national comprehensive building and safety code standards.

Varved Soil: Alternating layers of silt (or fine sand) and clay formed by variations in sedimentation; often exhibits contrasting colors when dried Vibratory Roller: A self-propelled flat steel drum or sheepsfoot roller that vibrates; the amplitude and frequency of the vibration can be adjusted on many rollers. Vibratory sheepsfoot-type rollers work well for compacting non-cohesive soils, whereas vibratory flat drum rollers compact aggregate base and asphalt well. Viscosity: The property of a fluid to resist internal flow

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Void: The space in a soil mass not occupied by solid mineral matter; the area (interstice) between soil particles; this zone may be occupied by air, water, or any other gas or liquid.

Woven Fabric: A geotextile fabric that has been strengthened by weaving the material together—allowing the fabric to have both stabilization and filtering properties

Void Ratio: The ratio of the volume of void space to the volume of solid particles in a given soil mass

Young’s Modulus (Elastic Modulus): The ratio of the increase of stress on a test specimen to the resulting increase in strain—while under constant transverse stress— limited to materials that have a linear stress–strain relationship over the range of loading

Volcanic Rock: See Igneous Rock. Water Content: The ratio of the weight of water contained within the pore space of a rock or soil sample to the dry solid weight of the sample— expressed as a percentage Water Table: The upper limit or surface of the saturated groundwater zone Weathered: A term used to describe rock that has been partially decomposed or disintegrated by the forces of nature over a period of time by such actions as wind, water, ice, and/ or chemical reactions Windrow: A long row of soil or other material formed by a blade or other grading equipment

Zero Air Voids Curve (ZAV Curve): (1) The curve drawn on the maximum density test graph to indicate the specific gravity and saturation point of a given material, used as a guide in plotting the maximum density curve; (2) the curve showing the zero air voids unit weight as a function of the water content Zone of Saturation: The area below the water table in which all pore spaces are fully filled with water— known as ground water

Index Figures are indicated by f and tables are indicated by t. active faults, 88 agency reviews, 16 alluvium, 86, 88 American Association of State Highway and Transportation Officials (AASHTO), 32 American Society for Testing and Materials (ASTM): D1556, 54; D1557, 34, 99; D2419, 75; D43187, 75; D6938, 54; International, 2, 32 Atterberg Limits Test, 4, 45 anchored floating solar array, 97, 98f artificial fill (AF), 3 auger: hollow-stem, 18–19; solid, 18 backfill area: creative backfill operation, 94f; hard-to-reach, 94f; testing, 151 backhoe trenches, 16, 25–26; depth to refusal, 26; ease/difficulty in digging, 26; hardness of excavation, 26; logs, 16, 26, 27f; steps, excavating, 26; safety guidelines, 26 basic laboratory tests, 32–49, 118–119; expansion pressure, 32; hydrometer analysis, 41–44; modified proctor/maximum density test, 33–38; particle size, 32; permeability, 32; plastic and liquid limits test, 45–49; plasticity index, 32; resistance (R) value, 32; results, 143f; sieve analysis, 38–41 bedrock, 26, 72, 78–80, 86, 130, 163; unstable, 87f, 88 bentonite, 45 best management practices (BMPs), 95, 105; treatment, 95–96 bioswale, 95f, 96 blasting, rock, 76f boreholes, 16, 18–21; plotting, 118; procedure, 18–19; standard penetration test (SPT), 18 boring logs, 16, 20f, 25, 69, 86, 104, 117, 138f–142f Brunton compass, 88, 89f California Modified Ring Sampler, 21f, 23f; barrel, 23f; N value for, 22t; padded storage box, 23f; rings, 23f carbonate cementation, 11t Casagrande, Arthur, 2 cemented formations, 26 Chinle Claystone Formation, 87f clay, 69, 80; compaction, 38; determining silt from, 5–7; expansive, 105; micaceous, 45; organic, 3; Plasticity Index (PI), 45; seams, 88

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Clean Water Act, 95 coefficient of curvature (Cc), 3 coefficient of uniformity (Cu), 3 compaction tests. See field density tests competent person, 148–151; definition, 150–151 consolidation tests, 21 curve sampling, 53; aggregate base, 53; subgrade, 53 Daily Field Report (DFR), 110, 111f daylighted bedding, 88 deep foundations, 77–79; hole diameter, 78; important areas of observation, 78–79; log report, 78; straightness of excavated shaft, 78; time and date of completion, 78; tip depth, 78; top elevation, 78 density test(s), 21, 70–71, 109, 153; aggregate base, 70; documentation, 110; failing, 94, 109; retests, 110; rock fill, 75; safety guidelines, 109 density test summary sheet, 112f dilatancy (shaking test), 6 direct shear tests, 21–22 direct transmission test, 70 drill rig, 17f drilled piers, 77 driven piles, 77 Environmental Protection Agency (EPA), 95 example project, 116–149; borehole and trench logging, 117–118; initial site visit, 117; laboratory testing, 118–119; scenario, 146; site investigation, 116 excavabiliity classification table, 28t Expansion Index test (EI), 45 Federal Highway Administration (FHWA), 32 field density tests, 34, 52–64; commonly used, 54; curve sampling, 53; importance of, 52; nuclear gauge test, 60–64, 75, 107; planning, 52–53; sand cone test, 54–60, 107; field dispersion test (settling time), 6–7 field sketch, 109f, 117 field soil classification, 2–12; care in, 2–3; descriptive terminology for soil types, 9t–12t; determining silt from clay, 5, 7; discerning fine sand from silt or clay, 5; distinguishing soil types, 5; quick reference for identifying fill or natural soil, 8t; recognizing fill or natural soil, 7–12; soil classification graphic chart, 49f; symbols, 3; symbols, dual, 3, 5; Unified Soil Classification System (USCS), 2, 5; Using the Field Classification Chart, 3, 4c, 5; writing soil descriptions, 3 flatland projects, 69 foundations, 77–79; density, 80; footing bottom material, 80; material, 88; placement of steel for, 80f; pouring, 80f; recommendations, 119; width and depth, 80; gabion baskets, 81f; geologic considerations, 86–89; on a grading project, 86–89; recognition and communication, 89 Geophysical Seismic Refraction Survey, 28 Geotechnical construction and green power and, 96–99 geotechnical investigation: expansion pressure test, 32; particle size test, 32; permeability test, 32; plasticity index test, 32; report, 16; resistance (R) value test, 32

Index

geotechnical report, 68–69, 72, 75, 92, 104, 116; acceptable fill material, 125; appendices, 135–143; benching, 129; clearing and grubbing, 125; conclusions, 124–125; cut/fill building pads, 127; density test frequency, 126; earthwork recommendations, 125–129; engineered fill replacement, 125–126; example, 118, 119–143; excavability, 124; exterior concrete flatwork, 127, 131; figures, 133f–134f; findings, 122–124; general removals, 124; groundwater, 124; introduction, 122; investigation and site conditions, 122; laboratory testing, 124, 143f; pavement areas, 127; pavement design, 131–132; pavement, rigid, 131–132; project location and description, 122; rock fill, 126–127; scope of services, 122; seismic parameters, 124–125; site geology, 123; slabs on grade, 130; slopes, 128–129; structural recommendations, 129–131; subgrade preparation, 125; subsurface conditions, 123; surface conditions, 123; surface drainage, 129; trench backfill, 127; trench excavations, 124; unstable subgrade mitigation options, 128 geothermal energy, 96; power plants, 96–97 geysers geothermal field, 96–97 grading: compaction equipment for, 92–94; in flat lands, 86; geologic concerns, 86–89; green, 95; hazardous features, 86–89; hillside, 86; low impact development (LID), 95; project safety, 152–153 grading plan review, 105 green power: anchored floating solar array, 97; geotechnical construction and, 96–99; geothermal energy, 96; geothermal power plant energy, 96–97; solar panels, 97f; wind turbines, 96 ground water seepage, 17f helical piles, 79f hillside grading, 72–77; areas of concern during, 72–74; bench, 72, 73f; buttress fill, 73f, 105; canyon fill, 73f, 74f; cleanout, 72; compaction equipment, 77; cut, fill, and transition pads, 77; drainage systems, 72; engineered fill, 74f; key, 73f, 105, 153; matrix soil, 74–75, 77; observation pit, 77; rock fill (oversize material) placement, 74–75, 77; rock fill (oversize material) placement, observation during, 75–77; slide removal, 105; slope faces, 72; subdrain, 74f, 105; testing and inspection, 72; utility trenches, 72 hydrometer analysis, 38, 41–44; apparatus, 41; calculations, 44; control readings, 42; dry weight of soil retained, 44; hydrometer readings, 42; procedure, 41–44; purpose, 41; test arrangement, 42f; test sheet, 42f, 44; values for L, 43t; values for K, 44t interlocking block walls, 81f jobsite soil construction, 68–82; deep foundations, 77–79; flatland projects, 69; hillside grading, 72–77; project preparation, 68–69; retaining and specialty walls, 81–82; road construction, 69–72; shallow foundations, 79–80 laboratory hydrometer test, 6 landslides, 87f; debris from, 88 lime treating, 99–101; compaction equipment, 99; dry, 100f; mixing depth, 99; mixing design, 99, 101f; placement, 99 low impact development (LID), 95; infiltration trenches, 95; vegetation bioswales, 95 maximum density test, 33–34, 52–53 maximum density value, 52–53 mica, 6–7

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modified Proctor/maximum density test, 33–38, 99; apparatus, 34–35; calculations and plot, 38; procedure, 35; synopsis of test results, 34; test sheet, 37f, 38 moisture tests, 21 montmorillonite, 45 Munsell color chart, 25 National Pollution Discharge Elimination System (NPDES), 95 nuclear gauge, 60–64, 75; calibrating, 64; downloading from, 60; memory, 60; radiation exposure, 61; radioactive material used, 60; safety, 60–61, 107; storage, 61f; training course in use, 61; transporting, 61 nuclear gauge test, 54f, 60–64, 107; advantages to, 62; backscatter method, 62; biases, 63–64; direct transmission method, 63; location, preparing, 62f; sidewall scatter, 64; taking a test, steps, 62, 63f; test hole, 55f Occupational Safety and Health Administration (OSHA), 26, 148, 149, 150 percent compaction, 52, 55 percent moisture, 34, 38, 48, 52, 69 phenolphthalein, 99, 100f plan of attack, 105 plastic and liquid limits test, 45–49; apparatus, 45; calculations, 48–49; graph plotting, 48–49; liquid limit, 45, 46; liquid limits device, 47–48; plastic limit, 45, 47–48; preparation (dry method), 46 procedure, 46–48; recording weight, 47–48; soil classification graphic chart, 49f; soil consistency for, 46; testing device, 46f; test sheet, 49f plasticity chart, 4 Plasticity Index (PI), 45, 49; definition, 45; non-plastic, 75 pocket penetrometer, 10t poured caisson shafts, 77 pre-grade/pre-job meetings, 105, 113, 116, 118 Project Data Sheet, 107, 108f project management and preparation, 104–113; communication, 107, 113; documentation, 110; observation, 105–107; project preparation, 104–105; technician’s steps to success, 110–113; testing, 107–110 radiation safety officer (RSO), 61 retaining and specialty walls, 81–82; footings, 82; gabion baskets, 81f; interlocking block walls, 81f; soil nail wall, drilling for placement, 82f road construction, 69–72; compaction, 69–72; preparation, 69–72; stabilizing with woven geotextile fabric, 71f; subgrade, preparing, 69–70; surface voids, 71 rock hardness study, 26–28; excavabiliity classification table, 28t; rippability investigation methods, 26 rotary drill barrel, 79 safety, 105, 113; backhoe trenches, 26; density tests, 109; grading project, 152–153; nuclear gauge, 60–61, 107; project site, 148–153; trench, 26, 106f, 148–152 sample: bags, labeling, 21, 26, 117; grabber, 19, 21; tags, 35f sampling, 5–7, 16–28, 117–118; backhoe trenches, 16, 25–26; boreholes, 16, 18–21; cone penetration test (CPT), 16; moving, 25; with rings, 21–23; rock hardness study, 26–28; seismic refraction, 16; thin-walled tube, 23–25

Index

sampling with rings, 21–23; California Modified Ring Sampler, 21f, 22t, 23f; drive shoe, 22; procedure, 21–23; removal of rings, 22; sampling barrel, 22, 23f; waste barrel, 22 sand cone test, 54–60, 107; apparatus, 55, 56d; calculations, 60; cone calibration, 55–56; dry density of soil, 60; in-place moisture content, 60; overview, 54–55; plate calibration, 55–56; procedure, 57–60; test biases, 60; test data sheet, 59f; test hole, 55f Santa Rosa Geyser Recharge Projet, 97 seismic: traverses, 28; waves, generating, 28 shallow foundations, 79–80; areas of concern, 80; foundations, density, 80; foundations, width and depth, 80 sieve analysis, 38–41; apparatus, 39; calculations, 41; procedure, 39–40; sieve arrangement, 39f; test sheet, 40f silt, 69; compaction, 38; determining clay from, 5–7; low-plastic, 38; non-plastic, 6; Plasticity Index (PI), 45; porous, 105 slope-wash, 88 soil: color, 7–8; compaction, 16, 68, 105; composition, 7; consistency, 10t, 11t; descriptions, writing, 3; depth of removal, 68; diatomaceous, 2; dry density, 34; dry strength, 6, 12t; fill, recognizing, 7, 8t, 9–12; gradation, 2, 3, 34; grain shape, 9t, 11t; grain size, 5t; gypsiferous, 2, 105; jobsite, construction, 68–82; micaceous, 2; moisture conditioning requirements, 16, 105; moisture content, 9t, 34, 35, 36; moisture limits, 68; natural, recognizing, 7, 8t, 9–12; non-plastic, 36, 47; odor, 3, 11t; organic, 2, 8, 88, 105; placement, 68; plasticity, 2, 12t, 69; porosity, 2, 7, 8, 80; removeable depths of unsuitable, 16; reports, 68; SM type, 35; topsoil, 88 soil classification graphic chart, 49f soil nail wall, 82f solar panels, 97f specialty piles, 78f split barrel sampler, 18f, 19 springs/seeps, 88 standard penetration test (SPT): 140-lb hammer/30–in. drop, 10t, 11t, 18; N value for, 19t; split barrel sampler, 18f, 19 standard Proctor, 33–34 stickiness test, 6 stormwater discharge, 95 stormwater low impact development (SWLID), 95f, 105 subgrade, preparing, 69–70; proof rolling, 70; unstable, 70 surface voids, 71 thin-walled tube sampling, 23–25; Pitcher sample barrel, 23; procedure, 24–25; rod chatter, 25; sample barrel, 25; Shelby sample barrel, 23 tremie hose, 78, 79f trench: compaction equipment for, 93t; excavations, 149–150; location, 118; log, 27f, 69, 86, 104, 117, 135f–137f; unsafe excavations, 151–152 trench safety guidelines, 26, 106f, 148–152 Trenching and Excavation Safety, 149 uncontrolled fill, 88 Unified Soil Classification System (USCS), 2, 5 US Army Corps of Engineers, 2 US Environmental Protection Agency (EPA), 95

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vermiculite, 45 volcanic flow, 26 water truck, 152f wind turbines, 96 woven geotextile fabrics, 70, 71f, 74f

About the Author

Tim is an avid hiker and rock-hounder, plays ice hockey and disc golf-in addition to dabbling in photography and poetry. Tim Davis resides in Santa Rosa, California, with his wife, Teresa. He works as senior public works inspector for the Town of Windsor in Sonoma County. During Tim’s career he has been involved in multiple phases of geotechnical construction, including investigation, lab and field testing, observation, inspection, report writing, supervision and training, and increasingly green construction and low impact development (LID). Tim holds an NICET Level IV as a geotechnical engineering technology generalist, and is certified as a qualified construction stormwater inspector, and MS4 LID/green inspector. This is an Endorsement of the book and some first hand experience with the author. “My involvement with geotechnical testing and observation has spanned many decades. During that time, my position has varied from junior technician to company owner. These positions have given me a solid perspective of the geotechnical business. Without a doubt, the biggest problem that the industry faces is the lack of a good training manual. But who should write it? Well, first, it should be a technician. Second, it should be one that knows every aspect of this diverse profession. And third, it should be someone who has the skill, the patience, and the resolve to compile all this information into a format that can be understood and appreciated by both new hires and veterans. Of all the technicians that I have met, Tim Davis fits this bill. Tim is one of those rare individuals who can take complex ideas and break them down into easy-tofollow steps. Consequently, his book is very user friendly. The first time that I had the pleasure of working with Tim, we performed field and lab quality control, as well as logging trenches and boreholes across the

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western US. Our paths have crossed many times since, and each time Tim has been in a well-respected position. Whether he was testing, training, troubleshooting, or supervising, Tim was always entrusted with the most difficult projects. Through the years, Tim has worked with both large and small geotechnical firms and municipalities. He has shared his experience to help contractors and quality control firms alike to adhere to the current best industry standards. I can’t think of anyone more qualified to write this book. I give it my whole-hearted endorsement.” Robert D. King, Senior Supervisory Inspector