ENGINEERING GEOLOGY FIELD MANUAL

8/9/2019 ENGINEERING GEOLOGY FIELD MANUAL

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ENGINEERING

GEOLOGY

FIEL

MANUAL

SECOND EDITION

VOLUME I

998

REPRINTED 2001

U S Department of the Interior

Bureau ofReclamation


2/449

The Mission of the

Department

of the

Interior

is to

protect and provide access to our

Nation s natural and

cultural

heritage and

honor

our

trust

responsibilities to

tribes

.

The Mission

ofth

e Bureau ofReclamation is to manage

develop and protect water and related resour es n

an

environmentally and

economically

sound manner in

the

interest of

the American public.

Information contained in this manual regarding

commercial products

or

firms

may not be used

for

advertising or promotional purposes and is not an

endorsement

of

any product or firm by the

Bureau of

Reclamation.

The

information contained in this manual was developed

for

th

e

Bureau

of Reclamation; no wtuT8Ilty

as to the

accuracy usefulness or completeness is expressed or

imolied.


3/449

Aclm owledgmenu

t r

Second dition

The

original compilation and p ~ p a r a t i o n

of this manual

involved

many

engineering geologists

and

geophysicists

withinReclamation. Theirinput sgreatlyappreciated.

This

second edition incorporates comments on the first edition

and

technological changes since the

first

edition was

prepared appro:limately 10 years ago. Without the

comments and

i JJ put

from the Denver, Regional, and Area

Offices

the

revision would not

have

happened. Special

thanks

to Sam

Bartlett, Engineering Geology Group 1

Manager, for

his support

and

input

throughout

the

preparation of the manual.

Although

there are

too

many

people to acknowledge

individually who contributed to the revisions and the second

edition,

Frank

Calcagno, Mel ill retired), Sandy

Kunzer

,

Jeff

Farrar,

SharoJ;l

Hebenstreit

, Linda Arrowwood, and

Peter

Rohrer

made

especially significant contributions.

Mark

McKeown contributed

to

and

edited

the

second edition.

Continued

recognition

ili

given

to Jerry

S. Dodd retired),

who initiated the

manual;

Jeny s

successor, Newcomb

Bennett

(retired),

who kept

the manual

moving; and

to

Steve D. Markwell retired), who

saw the first

edition

completed.

We extend

our thanks and appreciation

to

Louis

R

Frei, who helped establish

and document many

geological standards ofpractice,

and

to Richard H. Throner,

who wrote much of the original manual, who assembled

and

served on committees for preparation

and

review, to Sam

R

Bartlett

who compiled and printed the

early

loose

leaf

v e n ~ i o n of the

manual, and to Mel Hill

who completed the

publication of the first edition. To the g i o n a l Geologists

and their staffs and

the

many geotechnical

engineers

who

offered comments

that

have

been

mcorporated into

the

manual

we extend our thanks

and

appreciation for their

work s

well. The manual would not be oeomplete

with-out

the drawings

and

figures; to the engineering and physical

science

technicians

we extend our gratitude and thanks.


4/449


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FOREWORD

TO THE SECOND

EDITION

Approximately

10

years have gone by since the first

editionwas published,

and technolOgy

and

missions

have

changed

significantly. his second

edition

incorporates

many modifications and additions.

The

Global

Positioning System GPS) baa revolutionized how we

survey and locate OU1'8elves in the field

,

computers

are

used extensively ta

collect and evaluate

data, and

computer

aided

modeling, design, and drafting

are

almost

universal

. Reclamation

has

a

greater emphasis on

maintenance

and

safety

of

infrastnicture,

dam

safety

analyses

and modifications, and water resource

management

than

on

design and

construction

of

new

hydraulicstructures. Techniques

for

these

activities

and

environmental

restoration/hazardous

waste remediation

activities are reflected ill this edition.

A few

of

the

moat

significant

changes

to

the

manual

are

the

addition

of a section on concrete core logging, a

chapter

on hazard

ous waste site investigations, and

an

index to facilitate

finding

relevant information. Many

other

suggested

revisions and

improvements

collected

since the manual

was first published

also are

incorporated. he manum

now

is in

two uolumes

Volume I contains

material

commonly needed

in

the

field,

and

Volume II includes reference

or other material

.

As in the first edition, the

Engineering

Geolcgy kld

Manual presents

the practices for the collection of

geologic data obtained by the Burcnu of Reclamation.

The manual establishes common guidelines, procedures,

and

concepts for the collection,

evaluation,

and

presen-

tation

of

geologic

i.onnation. The

analyai.l

of

geologic

conditions, the

preparation

ofdesigns and specifications,

and

effective

construction monitoring and use of

geo-

logical information to assess site characteri.l tics and ri.l k,

require

consi.l tent, comprehen8ive,

and timely

geologic

v


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information.

The

use

of

these guidelines by all Recla-

mation engineering geologists collecting documenting

evaluating and presenting geological and geotechnical

data promotes consistency helps assure that the requind

evaluations

and

data

are

complete

and

promotes inte-

gration and coordination

of

geological

and

engineering

activities.

The Engineering Geology Field Manual

in

conjunction

with

the

Engineering

Geology Office Manual

forms the

basis for the mutually beneficial exchange of ideas by

Reclamation geologists. Experienced geologists w ll find

useful reminders

and

new procedures

and

special tech-

niques while less experienced engineering geologists and

those from

other

disciplines

can

use

the manual to

expand

their

familiarity

with

geology

as

practiced

in

the

Bureau of Reclamation.

Review and comments on the

manual are

encouraged

and

if

you

have

comments

or

suggested additions please

forward

them to the

Technical Service Center

Engineering Geology Groups.

Richard Throner

Leadership Team Member

Geotechnical Services

vi


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CONTENTS

Page

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . i i iForeword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

Chapter 1 Introduction . . . . . . . . . . . . . . . . . 1

Chapter 2 Geologic Terminology andClassifications for GeologicMaterials . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Established References for GeologicalTerminology . . . . . . . . . . . . . . . . . . . . . . . . 3

Geologic Classi fi cat ion of Mater ials . . . . . . . 4

Engineer ing Classificat ion of GeologicMater ials . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Appl ication and Use of Standard Indexes,Terminology, and Descr iptors . . . . . . . . . . 9

Uni ts of M easur ements for Geologic Logsof Explorat ion, Drawings, and Reports . . 12

Bibl iography . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Chapter 3 Engineering Classification andDescription of Soil . . . . . . . . . . . . . . . . . 17

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Classificat ions of Soi ls . . . . . . . . . . . . . . . . . . 21Abbreviated Soil Classif icat ion Symbols . . . 39Descr ipt ion of t he Physical Proper t ies

of Soi l . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40Narrat ive Descr ipt ions and Examples . . . . . 48Use of Soil Classification as Secondary

Ident i ficat ion Method for Mater ials

Other Than Natural Soi ls . . . . . . . . . . . . . 51

Bibl iography . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Chapter 4 Classification of Rocks andDescription of PhysicalProperties of Rock . . . . . . . . . . . . . . . . . 57

Int roduct ion . . . . . . . . . . . . . . . . . . . . . . . . . . 57Rock Classificat ion . . . . . . . . . . . . . . . . . . . . 57


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FIELD MANUAL

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Chapter 4 Classification of Rocks andDescription of PhysicalProperties of Rock(continued)

Page

Descr ipt ion of Rock . . . . . . . . . . . . . . . . . . . . 59

Example Descr ipt ions . . . . . . . . . . . . . . . . . . 86

Bibl iography . . . . . . . . . . . . . . . . . . . . . . . . . . 90

Chapter 5 Terminology and Descriptionsfor Discontinuities . . . . . . . . . . . . . . . . . 91

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

Indexes for Descr ibing Fractur ing . . . . . . . . 94

Descr ipt ion of Fractures . . . . . . . . . . . . . . . . 98Descripti ons of Shears and Shear Zones . . . 114

Bibl iography . . . . . . . . . . . . . . . . . . . . . . . . . . 126

Chapter 6 Geologic Mapping andDocumentation . . . . . . . . . . . . . . . . . . . . 129

Responsibi l i t ies of t he Engineer ingGeologist . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

Development of a St udy Plan . . . . . . . . . . . . 130

Speci fic Mapping Requi rements . . . . . . . . . . 133Global Posit ioning Syst em . . . . . . . . . . . . . . 135

Site Mapping . . . . . . . . . . . . . . . . . . . . . . . . . 153Dozer Trench Mapping . . . . . . . . . . . . . . . . . 157Backhoe Trench Mapping . . . . . . . . . . . . . . . 161

Const ruct ion Geologic Mapping . . . . . . . . . . 167

L ar ge Excavat ion M apping . . . . . . . . . . . . . . 168Steep Slope Mapping . . . . . . . . . . . . . . . . . . . 169

Canal and Pipel ine Mapping . . . . . . . . . . . . 170

Underground Geologic Mapping . . . . . . . . . 171Underground Geologic Mapping Methods . . 185

Photogeologic Mapping . . . . . . . . . . . . . . . . . 196

Analysis of Aer ial Photographs . . . . . . . . . . 198


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CONTENTS

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Chapter 6 Geologic Mapping andDocumentation(continued)

Page

Photoanalysis for ReconnaissanceGeologic Mapping . . . . . . . . . . . . . . . . . . . . 199

Availabi l i ty of Imagery . . . . . . . . . . . . . . . . . 200

References . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

Bibl iography . . . . . . . . . . . . . . . . . . . . . . . . . . 203

Chapter 7 Discontinuity Surveys . . . . . . . . 205General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205Bibl iography . . . . . . . . . . . . . . . . . . . . . . . . . . 211

Chapter 8 Exploration DrillingPrograms . . . . . . . . . . . . . . . . . . . . . . . . . 213

Int roduct ion . . . . . . . . . . . . . . . . . . . . . . . . . . 213

Preparation of Dr i l l ing Speci ficati onsand Format . . . . . . . . . . . . . . . . . . . . . . . . . 223

Chapter 9 Groundwater Data AcquisitionMethods . . . . . . . . . . . . . . . . . . . . . . . . . . . 227

Int roduct ion . . . . . . . . . . . . . . . . . . . . . . . . . . 227

Design and Installation of ObservationWel ls and Piezometers . . . . . . . . . . . . . . . 229

Methods Used t o Measure Groundwater

Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235

Methods and Techniques Used t o EstimateFlows fr om Seeps, Spr ings, and Small

Drainages . . . . . . . . . . . . . . . . . . . . . . . . . . 241

Computer-Based Monitoring Systems . . . . . 242Definit ions . . . . . . . . . . . . . . . . . . . . . . . . . . . 245

References . . . . . . . . . . . . . . . . . . . . . . . . . . . 246Bibl iography . . . . . . . . . . . . . . . . . . . . . . . . . . 247


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FIELD MANUAL

x

Chapter 10 Guidelines for Core Logging . 249General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249

Format and Requir ed Data for the Final

Geologic Log . . . . . . . . . . . . . . . . . . . . . . . . 252Method of Repor t ing Or ientati on of Planar

Discontinuit ies and Str uctural Features . 284

Core Recovery and Core Losses . . . . . . . . . . 285Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287

Core Photography . . . . . . . . . . . . . . . . . . . . . 288

Equipment Necessary for Preparing

Field Logs . . . . . . . . . . . . . . . . . . . . . . . . . . 291Inst ruct ion to Dr i l lers, Dai ly Dr i l l Repor ts,

and General Dr i l ling Procedures . . . . . . . . 294

Chapter 11 Instructions for Logging Soils 313General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313Formats for Test Pit s and Auger Hole Logs 325

Format of Word Descr ipt ions for Dr i l l Hole Logs . . . . . . . . . . . . . . . . . . . . . . . . . . . 333Except ions to Test Pit and Auger Hole

Format and Descr ipt ions for Dr i l l

Hole Logs . . . . . . . . . . . . . . . . . . . . . . . . . . 339Equipment Necessary for Preparing the

Field Log . . . . . . . . . . . . . . . . . . . . . . . . . . . 347

Example Descr ipt ions and Format . . . . . . . . 349

Laboratory Classi ficat ions in Addit ion t oVisual Classificat ions . . . . . . . . . . . . . . . . 349

Word Descr ipt ions for Var ious Soi lClassificat ions . . . . . . . . . . . . . . . . . . . . . . . 351

Repor ting L abor at ory Dat a . . . . . . . . . . . . . . 351

Special Cases for USCS Classificati on . . . . . 363Repor t ing In-Place Densi ty Tests . . . . . . . . . 364

Bibl iography . . . . . . . . . . . . . . . . . . . . . . . . . . 366


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CONTENTS

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Page

Chapter 12 Hazardous Waste Site

Investigations . . . . . . . . . . . . . . . . . . . . . 367General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367

Common Terminology and Processes . . . . . . 368Documentat ion . . . . . . . . . . . . . . . . . . . . . . . . 369

Contaminant Character ist ics and

Migrat ion . . . . . . . . . . . . . . . . . . . . . . . . . . 375Classif icat ion and Handling of Materials . . 381

Field Sampling Protocol . . . . . . . . . . . . . . . . 383Sample Analysis . . . . . . . . . . . . . . . . . . . . . . 402Safety at Hazardous Waste Si tes . . . . . . . . . 405

Sample Quali ty Assurance and

Quali ty Cont rol . . . . . . . . . . . . . . . . . . . . . 406Sample Management . . . . . . . . . . . . . . . . . . . 410

Decontaminat ion . . . . . . . . . . . . . . . . . . . . . . 417

AppendixAbbreviations and Acronyms CommonlyUsed in Bureau of ReclamationEngineering Geology and Related toHazardous Waste . . . . . . . . . . . . . . . . . . . . 419

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433

TABLES

Table Page

2-1 Ground behavior for eart h tunnelingwith steel suppor ts . . . . . . . . . . . . . . . 10

2-2 Useful conversion factorsmetr ic andEngl ish unit s (inch-pound) . . . . . . . . . 14

3-1 Basic gr oup names, pr imar y gr oups . . . 26


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FIELD MANUAL

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TABLES (continued)

Table Page

3-2 Basic group names, 5 to 12 percent

fines . . . . . . . . . . . . . . . . . . . . . . . . . . . 263-3 Cr iter ia for descr ibing dry st rength . . . 31

3-4 Cr iter ia for descr ibing di latancy . . . . . . 32

3-5 Cr iter ia for descr ibing toughness . . . . . 333-6 Cr iter ia for descr ibing plast ici ty . . . . . . 34

3-7 Identif icati on of inorganic f ine-grainedsoi ls from manual tests . . . . . . . . . . . 36

3-8 Crit eria for describing angularit y of

coar se-gr ained par ticles . . . . . . . . . . . 41

3-9 Cr it er ia for descr ibing par t i cl e shape . . 423-10 Cri teri a for describing moisture

condit ion . . . . . . . . . . . . . . . . . . . . . . . 43

3-11 Cri teri a for describing react ionwith HCl . . . . . . . . . . . . . . . . . . . . . . . 43

3-12 Cr it er ia for descr ibing consistency of

in-place or undisturbed fine-grainedsoi ls . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

3-13 Cr it er ia for descr ibing cementat ion . . . 44

3-14 Cr it er ia for descr ibing st ruct ur e . . . . . . 453-15 Par t icle sizes . . . . . . . . . . . . . . . . . . . . . . 46

3-16 Checkl ist for the descr iption of soilclassi ficat ion and ident i ficat ion . . . . . 48

3-17 Checkl ist for the descr iption of in-place

condit ions . . . . . . . . . . . . . . . . . . . . . . . . 49

4-1 Igneous and metamorphic rock grainsize descr iptors . . . . . . . . . . . . . . . . . . 70

4-2 Sedimentary and pyroclastic rock

par ticle-size descr ipt or s . . . . . . . . . . . 714-3 Bedding, fol iat ion, or f low texture

descr iptors . . . . . . . . . . . . . . . . . . . . . . . 74

4-4 Weather ing descr iptors . . . . . . . . . . . . . 774-5 Durabi l i ty index descr iptors . . . . . . . . . 79


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CONTENTS

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TABLES (continued)

Table Page

4-6 Rock har dness/st rengt h descr ipt or s . . . 835-1 Fracture density descr iptors . . . . . . . . . 97

5-2 Fracture spacing descr iptors . . . . . . . . . 102

5-3 Fr act ur e cont inuit y descr ipt or s . . . . . . . 1025-4 Descriptors for recording fracture ends

in joint surveys . . . . . . . . . . . . . . . . . . 1035-5 Fr act ur e openness descr ipt or s . . . . . . . . 1045-6 Fracture fi ll ing thickness descr iptors . . 104

5-7 Fracture heal ing descr iptors . . . . . . . . . 107

5-8 Fr act ur e r oughness descr ipt or s . . . . . . . 1095-9 Fracture moisture condit ions

descr iptors . . . . . . . . . . . . . . . . . . . . . . 110

6-1 U.S. State plane coordinate systems 1927 datum . . . . . . . . . . . . . . . . . . . . . 137

6-2 U.S. State plane coordinate systems

1983 datum . . . . . . . . . . . . . . . . . . . . . 14311-1 Checkl ist for the descr iption of soil s in

test pi t and auger hole logs . . . . . . . . 326

12-1 EPA recommended sampling containers,preservation requirements, and

holding t imes for soi l samples . . . . . . 38512-2 Summary of soi l sampl ing devices . . . . 38812-3 Common laboratory test ing methods . . 404

FIGURES

Figure Page

3-1 Modifiers t o basic soi l gr oup names . . . 223-2 Flow chart for i norganic f ine-grained

soi ls, visual method . . . . . . . . . . . . . . 23


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FIELD MANUAL

xiv

FIGURES (continued)

Figure Page

3-3 Flow chart for organic soils, visual

method . . . . . . . . . . . . . . . . . . . . . . . . . 24

3-4 Flow chart for coarse-grained soils,visual method . . . . . . . . . . . . . . . . . . . 25

3-5 Plast ici ty char t . . . . . . . . . . . . . . . . . . . . 35

3-6 Sample of test results summary . . . . . . 534-1 Field classi fi cat ion of i gneous rocks . . . 60

4-2 Field classif ication of sedimentary

rocks . . . . . . . . . . . . . . . . . . . . . . . . . . . 614-3 Field classif icat ion of metamorphic

rocks . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

4-4 Field classi ficat ion of pyroclast ic rocks . 634-5 Chart s for estimating percentage of

composit ion of rocks and sediments . 644-6 Descriptor legend and explanation

example . . . . . . . . . . . . . . . . . . . . . . . . 67

4-7 Permeabil i ty conversion char t . . . . . . . . 87

5-1 Rock Quality Designation (RQD)computat ion . . . . . . . . . . . . . . . . . . . . . 96

5-2 Comparison of tr ue and apparent

spacing . . . . . . . . . . . . . . . . . . . . . . . . . 1015-3 Examples of roughness and waviness of

fr acture sur faces, typical roughness

profi les, and t erminology . . . . . . . . . . 1085-4 Uniform shear zone . . . . . . . . . . . . . . . . 115

5-5 Str uctured shear zone (two zones or

layers) . . . . . . . . . . . . . . . . . . . . . . . . . 116

5-6 St ructured shear zone (three layers) . . 1165-7 Uniform shear zone wit h veinlet s . . . . . 116

5-8 Unifor m shear zone (composit e) . . . . . . 1175-9 Standard descriptors and descriptive

cr it er ia for di scont inui ti es . . . . . . . . . 121


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CONTENTS

xv

FIGURES (continued)

Figure Page

6-1 Process of engineer ing geology

mapping . . . . . . . . . . . . . . . . . . . . . . . . 131

6-2 Sample t rench log . . . . . . . . . . . . . . . . . . 1606-3 Sample completed t rench log . . . . . . . . . 165

6-4 Tunnel mapping form wi th key

alphanumeric descr iptors andmapping data . . . . . . . . . . . . . . . . . . . 173

6-5 Tunnel mapping form with blocks for

t i t le and geologic data . . . . . . . . . . . . 1746-6 As-bui lt summary geology tunnel map . 179

6-7 Ful l per iphery mapping method

layout . . . . . . . . . . . . . . . . . . . . . . . . . . 1866-8 Ful l per iphery geologic map example . . 188

6-9 Map layout of a tunnel for geologicmapping . . . . . . . . . . . . . . . . . . . . . . . . 191

6-10 Relationship of planar feature t race to

map project ions . . . . . . . . . . . . . . . . . . 192

7-1 Equator ial equal area net . . . . . . . . . . . 2097-2 Discont inuity log field sheet . . . . . . . . . 210

10-1 Dr i l l hole log, DH-123 . . . . . . . . . . . . . . 253

10-2 Dril l hole log, B-102, for Standard Penet rat ion Test . . . . . . . . . . . . . . . . . 255

10-3 Dr i l l hole log, DH-SP-2 . . . . . . . . . . . . . 259

10-4 Dr i l l hole log, SPT-107-2 . . . . . . . . . . . . 26110-5 Dr il l hole log, DH-DN/P-60-1 . . . . . . . . . 270

10-6 Daily dr i l l repor t . . . . . . . . . . . . . . . . . . 292

10-7 Water test ing record . . . . . . . . . . . . . . . 299

10-8 Use of hal f-round to protect core . . . . . . 30110-9 Standard N-size core box . . . . . . . . . . . . 303

10-10 Log of concrete and rock core . . . . . . . . . 30811-1 L og of t est pit or auger hole . . . . . . . . . . 314

11-2 Clean coar se-gr ained soi ls . . . . . . . . . . . 315


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FIELD MANUAL

xvi

FIGURES (continued)

Figure Page

11-3 Fine-grained soi ls . . . . . . . . . . . . . . . . . . 316

11-4 Soil classificat ions based on laboratory

test data . . . . . . . . . . . . . . . . . . . . . . . . 31711-5 Auger hole wit h samples t aken . . . . . . . 318

11-6 Repor t ing laboratory classificat ion in

addi t ion to visual classi ficat ion . . . . . 31911-7 Undisturbed soi ls . . . . . . . . . . . . . . . . . . 320

11-8 Coarse-grained soi ls wi th fines . . . . . . . 321

11-9 Coarse-grained soil s wit h dualsymbols . . . . . . . . . . . . . . . . . . . . . . . . 322

11-10 Repor t ing in-place density tests and

percent compact ion . . . . . . . . . . . . . . . 32311-11 Soil wi th measured percentages of

cobbles and boulder s . . . . . . . . . . . . . . 32411-12 Field form - soi l logging . . . . . . . . . . . . . 32911-13 Soil with more than 50 percent cobbles

and boulders . . . . . . . . . . . . . . . . . . . . 334

11-14 Border l ine soi ls . . . . . . . . . . . . . . . . . . . . 33511-15 Test pit wit h samples t aken . . . . . . . . . 336

11-16 Disturbed samples . . . . . . . . . . . . . . . . . 337

11-17 Two descr ipti ons from t he samehor izon . . . . . . . . . . . . . . . . . . . . . . . . . 338

11-18 Dr i l l hole advanced by tr i-cone

rock bit . . . . . . . . . . . . . . . . . . . . . . . . . 34011-19 Log showing poor r ecovery . . . . . . . . . . . 342

11-20 Log of l andsl ide mater ial (a) . . . . . . . . . 343

11-21 Log of l andsl ide mater ial (b) . . . . . . . . . 344

11-22 Log of bedrock . . . . . . . . . . . . . . . . . . . . . 34511-23 Geologic int erpretat ion in t est pit

(sheet 1) . . . . . . . . . . . . . . . . . . . . . . . . 35011-24 Geologic int erpretat ion in test pit

(sheet 2) . . . . . . . . . . . . . . . . . . . . . . . . 352


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CONTENTS

xvii

FIGURES (continued)

Figure Page

11-25 Geologic int erpretat ion in test pit using

a geologic profi le (1) . . . . . . . . . . . . . . 353

11-26 Geologic int erpretat ion in test pit(sheet 3) . . . . . . . . . . . . . . . . . . . . . . . . 354

11-27 Geologic int erpretat ion in test pit

(sheet 4) . . . . . . . . . . . . . . . . . . . . . . . . 35511-28 Geologic int erpretat ion in test pit using

a geologic profi le (2) . . . . . . . . . . . . . . 356

11-29 Geologic int erpretat ion in test pit(sheet 5) . . . . . . . . . . . . . . . . . . . . . . . . 357

11-30 Geologic int erpretat ion in test pit



(sheet 8) . . . . . . . . . . . . . . . . . . . . . . . . 360

11-33 Geologic int erpretat ion in test pit using

a geologic profi le (3) . . . . . . . . . . . . . . 36112-1 Aquifer types . . . . . . . . . . . . . . . . . . . . . . 379

12-2 Typical monitor ing well const ruct ion for

wat er qual i t y sampling . . . . . . . . . . . . 39912-3 Soil and water sample identificati on

labels . . . . . . . . . . . . . . . . . . . . . . . . . . 412

12-4 Chain-of-custody record . . . . . . . . . . . . . 41312-5 Custody seal . . . . . . . . . . . . . . . . . . . . . . 415


18/449


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Chapter 1

INTRODUCTION

This manual provides guidelines and instructions for

performing and documenting field work. The manual is

a ready reference for anyone engaged in field-oriented

engineering geology or geotechnical engineering. The

manual is written for general engineering geology use as

well as to meet Reclamation needs. The application of

geology to solving engineering problems is emphasized,

rather than academic or other aspects of geology. Themanual provides guidance for:

Geologic classification and description of rock and

rock discontinuities

Engineering classification and description of soil

and surficial deposits

Application of standard indexes, descriptors, and

terminology

Geologic mapping, sampling, testing, and

performing discontinuity surveys

Exploratory drilling

Soil and rock logging

Acquisition of groundwater data

Core logging

Soil logging

Investigation of hazardous waste sites


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FIELD MANUAL

2

Although the methods described in this manual are

appropriate for most situations, complex sites, conditions,

or design needs may require modification or expansion of

the suggestions, criteria, and indices to fit specificrequirements.

Many of the chapters in this manual will always need

revision because they cover material that changes as

technology changes. Critical comments, especially sug-

gestions for improvement, are welcome from all users,

not just the Bureau of Reclamation.

The appendix contains abbreviations and acronyms

commonly used in engineering geology.


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1Brackets refer to bibliography entries at end of each chapter.

Chapter 2

GEOLOGIC TERMINOLOGY

AND CLASSIFICATIONS FOR

GEOLOGIC MATERIALS

Established References for Geological

Terminology

Adaptations or refinements of the Bureau of Reclamation

(Reclamation) standards presented in this and subse-quent chapters may be established to meet specific design

requirements or site-specific geologic complexity when

justified.

The Glossary of Geology, Fourth Edition [1]1, published by

the American Geological Institute (AGI), 1997, is accepted

by Reclamation as the standard for definitions of geologic

words and terms except for the nomenclature, definitions,

or usage established in this chapter and chapters 3, 4,

and 5.

The North American Stratigraphic Code (NASC) [2] is the

accepted system for classifying and naming stratigraphic

units. However, Reclamation's engineering geology pro-

grams are focused primarily on the engineering prop-erties of geologic units, not on the details of formal

stratigraphic classification. Stratigraphic names are not

always consistent within the literature, often change from

one locality to another, and do not necessarily convey

engineering properties or rock types. Use of stratigraphic

names in Reclamation documents normally will be

informal (lower case) (see NASC for discussion of formalversus informal usage). Exceptions to informal usage are

for names previously used formally in the area in discus-

sions of geologic setting or regional geology. Normally,


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FIELD MANUAL

4

the first use of formal names in a report should include a

reference to a geologic map or publication in which the

term is defined.

Geologic Classification of Materials

The following definitions of geologic materials more fully

satisfy general usage and supersede those in the Glossary

of Geology. These definitions are for geologic classifica-

tion of materials. They should not be confused with engi-neering classifications of materials such as rock and soil

or rock and common excavation.

Bedrockis a general term that includes any of the gen-

erally indurated or crystalline materials that make up the

Earth's crust. Individual stratigraphic units or units sig-

nificant to engineering geology within bedrock may in-clude poorly or nonindurated materials such as beds,

lenses, or intercalations. These may be weak rock units

or interbeds consisting of clay, silt, and sand (such as the

generally soft and friable St. Peter Sandstone), or clay

beds and bentonite partings in siliceous shales of the

Morrison Formation.

Surficial Depositsare the relatively younger materialsoccurring at or near the Earth's surface overlying bed-

rock. They occur as two major classes: (1) transported

deposits generally derived from bedrock materials by

water, wind, ice, gravity, and man's intervention and

(2) residual deposits formed in place as a result of

weathering processes. Surficial deposits may be stratified

or unstratified such as soil profiles, basin fill, alluvial orfluvial deposits, landslides, or talus. The material may be

partially indurated or cemented by silicates, oxides,

carbonates, or other chemicals (caliche or hardpan). This

term is often used interchangeably with the imprecisely


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TERMINOLOGY

5

defined word overburden. Overburden is a mining

term meaning, among other things, material overlying a

useful material that has to be removed. Surficial

deposit is the preferred term.

In some localities, where the distinction between bedrock

and surficial deposits is not clear, even if assigned a

stratigraphic name, a uniform practice should be estab-

lished and documented and that definition followed for

the site or study.

Guidelines for the collection of data pertaining to bedrock

and surficial deposits are presented in chapter 6.

Engineering Classification of Geologic

Materials

General

Geologic classification of materials as surficial deposits or

bedrock is insufficient for engineering purposes. Usually,

surficial deposits are described as soil for engineering

purposes, and most bedrock is described as rock; however,

there are exceptions. Contract documents often classify

structure excavations as to their ease of excavation. Also,classification systems for tunneling in geologic materials

have been established.

Classification as Soil or Rock

In engineering applications, soilmay be defined as gener-

ally unindurated accumulations of solid particlesproduced by the physical and/or chemical disintegration

of bedrock and which may or may not contain organic

matter. Surficial deposits, such as colluvium, alluvium,

or residual soil, normally are described using Recla-


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FIELD MANUAL

6

mation Procedure 5005, Determining Unified Soil

Classification (Visual Method) [3]. American Society for

Testing and Materials (ASTM) Standards D2487-85,

Standard Test Method for Classification of Soils forEngineering Purposes or D2488-84, Standard Practice for

Description and Identification of Soils (Visual-Manual

Procedure), which are based on Reclamation 5000 and

5005 [3] also may be used. Instructions for the

description and classification of soils are provided in

chapter 3. Chapter 11 provides instructions for the

logging of soils in geologic explorations. In some cases,partially indurated soils may have rock-like

characteristics and may be described as rock.

The United States Department of Agriculture (USDA)

Agricultural Soils Classification System is used for drain-

age and land classification and some detailed Quaternary

geology studies, such as for seismotectonic investigations.

Rock as an engineering material is defined as lithified or

indurated crystalline or noncrystalline materials. Rock

is encountered in masses and as large fragments which

have consequences to design and construction differing

from those of soil. Field classification of igneous,

metamorphic, sedimentary, and pyroclastic rocks are

provided in chapter 4. Chapter 4 also presents asuggested description format, standard descriptors, and

descriptive criteria for the lithologic and engineering

physical properties of rock. Nonindurated materials with-

in bedrock should be described using the Reclamation soil

classification standards and soil descriptors presented in

chapter 3. Engineering and geological classification and

description of discontinuities which may be present ineither soil or rock are discussed in chapter 5.


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TERMINOLOGY

7

Classification of Excavations

The engineering classification of excavation as either rock

excavation or common excavation or the definition of rockin specifications must be evaluated and determined for

each contract document and should be based on the

physical properties of the materials (induration and other

characteristics), quantity and method of excavation, and

equipment constraints and size.

Classification of Materials for Tunneling

Classification systems are used for data reports, speci-

fications, and construction monitoring for tunnel designs

and construction. When appropriate for design, other

load prediction and classification systems may be used

such as the Q system developed by the Norwegian Geo-

technical Institute (NGI), Rock Mass Rating System

Geomechanics Classification (RMR), and Rock Structure

Rating (RSR).

The following terms for the classification of rock [4] for

tunneling are suggested:

Intact rockcontains neither joints nor hairline cracks.

If it breaks, it breaks across sound rock. On account ofdamage to the rock due to blasting, spalls may drop off

the roof several hours or days after blasting. This is

known as spalling condition. Hard, intact rock may also

be encountered in the popping condition (rock burst)

involving the spontaneous and violent detachment of rock

slabs from sides or roof.

Stratified rockconsists of individual strata with little

or no resistance against separation along the boundaries


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FIELD MANUAL

8

between strata. The strata may or may not be weakened

by transverse joints. In such rock, the spalling condition

is quite common.

Moderately jointed rockcontains joints and hairline

cracks, but the blocks between joints are locally grown

together or so intimately interlocked that vertical walls

do not require lateral support. In rocks of this type, both

the spalling and the popping condition may be

encountered.

Blocky and seamy rockconsists of chemically intact

or almost intact rock fragments which are entirely

separated from each other and imperfectly interlocked.

In such rock, vertical walls may require support.

Crushed but chemically intact rockhas the char-

acter of a crusher run. If most or all of the fragments areas small as fine sand and no recementation has taken

place, crushed rock below the water table exhibits the

properties of a water-bearing sand.

Squeezing rock slowly advances into the tunnel

without perceptible volume increase. Movement is the

result of overstressing and plastic failure of the rock mass

and not due to swelling.

Swelling rockadvances into the tunnel chiefly on ac-

count of expansion. The capacity to swell is generally

limited to those rocks which contain smectite, a

montmorillonite group of clay minerals, with a high

swelling capacity.

Although the terms are defined, no distinct boundaries

exist between rock categories. Wide variations in the

physical properties of rocks classified by these terms and

rock loading are often the case.


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TERMINOLOGY

9

Table 2-1, Ground behavior for earth tunneling with steel

supports, provides ground classifications for different

reactions of ground to tunneling operations.

Application and Use of Standard Indexes,

Terminology, and Descriptors

This section and subsequent chapters 3, 4, and 5 provide

definitions and standard descriptors for physical

properties of geologic materials which are of engineeringsignificance. The ability of a foundation to support loads

imposed by various structures depends primarily on the

deformability and stability of the foundation materials

and the groundwater conditions. Description of geologic

and some manmade materials (embankments) is one of

the geologist's direct contributions to the design process.

Judgment and intuition alone are not adequate for the

safe and economical design of large complex engineering

projects. Preparation of geologic logs, maps and sections,

and detailed descriptions of observed material is the least

expensive aspect and most continuous record of a sub-

surface exploration program. It is imperative to develop

design data properly because recent advances in soil and

rock mechanics have enabled engineers and geologists to

analyze more conditions than previously possible. Theseanalyses rely on physical models that are developed

through geologic observation and which must be

described without ambiguity.

The need for standard geologic terminology, indexes, and

descriptors has long been recognized because it is

important that design engineers and contractors, aswell as geologists, be able to have all the facts and quali-

tative information as a common basis to arrive at

conclusions from any log of exploration, report, or draw-

ing, regardless of the preparer. Geologic terminology,


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FIELD MANUAL

10

Table 2-1.Ground behavior for earth tunneling withsteel supports (after Terzaghi, 1977) [4]

Ground classification Reaction of ground to tunneling operation

HARD Tunnel heading may be advanced without roof support.FIRM Ground in which a roof section of a tunnel can be left

unsupported for several days without inducing a

perceptible movement of the ground.

RAVELING Chunks or flakes of soil begin to drop out of roof at some

point during the ground-movement period.

SLOW RAVELING The time required to excavate 5 feet of tunnel and

install a rib set and lagging in a small tunnel is about

6 hours. Therefore, if the stand-up time of raveling

ground is more than 6 hours, by using ribs and lagging,

the steel rib sets may be spaced on 5-foot centers. Sucha soil would be classed as slow raveling.

FAST RAVELING If the stand-up time is less than 6 hours, set spacing

must be reduced to 4 feet, 3 feet, or even 2 feet. If the

stand-up time is too short for these smaller spacings,

liner plates should be used, either with or without rib

sets, depending on the tunnel size.

SQUEEZING Ground slowly advances into tunnel without any signs

of fracturing. The loss of ground caused by squeeze and

the resulting settlement of the ground surface can be

substantial.

SWELLING Ground slowly advances into the tunnel partly or chiefly

because of an increase in the volume of the ground. The

volume increase is in response to an increase of water

content. In every other respect, swelling ground in a

tunnel behaves like a stiff non-squeezing, or slowly

squeezing, non-swelling clay.

RUNNING The removal of lateral support on any surface rising at

an angle of more than 34E(to the horizontal) is

immediately followed by a running movement of the soil

particles. This movement does not stop until the slope

of the moving soil becomes roughly equal to 34E if

running ground has a trace of cohesion, then the run is

preceded by a brief period of progressive raveling.

VERY SOFT SQUEEZING Ground advances rapidly into tunnel in a plastic flow.

FLOWING Ground supporting a tunnel cannot be classified as

flowing ground unless water flows or seeps through it

toward the tunnel. For this reason, a flowing condition

is encountered only in free air tunnels below the

watertable or under compressed air when the pressureis not high enough in the tunnel to dry the bottom. A

second prerequisite for flowing is low cohesion of soil.

Therefore, conditions for flowing ground occur only in

inorganic silt, fine silty sand, clean sand or gravel, or

sand-and-gravel with some clay binder. Organic silt

may behave either as a flowing or as a very soft,

squeezing ground.


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TERMINOLOGY

11

standard descriptors, and descriptive criteria for physical

properties have been established so that geologic data are

recorded uniformly, objectively, consistently, and accu-

rately. The application of these indexes, terminology,descriptors, and various manual and visual tests must be

applied consistently by all geologists for each particular

project. The need to calibrate themselves with others per-

forming similar tests and descriptions is imperative to

ensure that data are recorded and interpreted uniformly.

The use of these standard descriptors and terminology is

not intended to replace the geologist's or engineer's indi-vidual judgment. The established standard qualitative

and quantitative descriptors will assist newly employed

geologists and engineers in understanding Reclamation

terminology and procedures, permit better analysis of

data, and permit better understanding by other geologists

and engineers, and by contractors. Most of the physical

dimensions established for the descriptive criteria per-

taining to rock and discontinuity characteristics have

been established using a 1-3-10-30-100 progression for

consistency, ease of memory, conversion from English to

metric (30 millimeters [mm] = 0.1 foot [ft]) units, and to

conform to many established standards used throughout

the world. Their use will improve analysis, design and

construction considerations, and specifications prepara-

tion. Contractor claims also should be reduced due toconsistent and well defined terminology and descriptors.

Alphanumeric values for many physical properties have

been established to enable the geotechnical engineer and

engineering geologist to readily analyze the geologic data.

These alphanumeric descriptors also will assist in compi-

lation of data bases and computer searches when usingcomputer generated logs. For consistency, the lower the

alphanumeric value, the more favorable the condition

being described. However, alphanumeric codes do not

replace a complete description of what is observed. A


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FIELD MANUAL

12

complete description provides physical dimensions

including a range and/or average in size, width, length or

other physical property, and/or descriptive information.

It is important to start physical testing of the geologic

materials as early as possible in an exploration program;

descriptors alone are not sufficient. As data are inter-

preted, index properties tests can be performed in the

field to obtain preliminary strength estimates for repre-

sentative materials or materials requiring special con-

sideration. The scope of such a program must be tailoredto each feature. Tests which are to be considered include

point load, Schmidt hammer, sliding tilt, and pocket

Torvane or penetrometer tests. These tests are described

briefly in chapters 4 and 5. Indexes to be considered

include rock hardness, durability (slaking), and Rock

Quality Designation (RQD). The type of detailed labora-

tory studies can be formulated better and the amount of

sampling and testing may be reduced if results from field

tests are available.

Units of Measurements for Geologic Logs of

Exploration, Drawings, and Reports

Metric Units

For metric specifications and studies, metric (Interna-

tional System of Units) should be used from the start of

work if possible. Logs of exploration providing depth

measurements should be given to tenths or hundredths of

meters. All linear measurements such as particle or

crystal sizes, ranges or averages in thickness, openness,and spacing, provided in descriptor definitions in

chapters 3, 4, and 5, should be expressed in millimeters

or meters as appropriate. Pressures should be given in

pascals (Pa). Permeability (hydraulic conductivity)


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TERMINOLOGY

13

should be in centimeters per second (cm/s). In some

cases, local usage of other units such as kilogram per

square centimeter (kg/cm2) for pressure or centimeters

(cm) may be used.

English Units (U.S. Customary)

For specifications and studies using United States cus-

tomary or English units (inch-pound), depth measure-

ments should be given in feet and tenths of feet. Ranges

in thickness, openness, and spacing, are preferred intenths or hundredths of a foot, or feet as shown in the

descriptor definitions in chapters 4 and 5. Pressure

should be in pound-force per square inch (lbf/in2 or

PSI). Permeability should be in feet per year (ft/yr). The

exceptions to the use of English units (inch-pound) are for

describing particle and grain sizes and age dating.

Particle sizes for soils classified using American Society

for Testing and Materials/Unified Soil Classification

Systems (ASTM/USCS) should be in metric units on all

logs of exploration. For description of bedrock, particle

and grain sizes are to be in millimeters.

Age Dates

If age dates are abbreviated, the North American Strati-graphic Commission (NASC) recommends ka for thousand

years andMa for million years, but my or m.y. (million

years) for time intervals (for example, ". . . during a

period of 40 my . . .").

Conversion of Metric and English (U.S. Customary)

Units

Table 2-2 provides many of the most frequently used

metric and English (U.S. Customary) units for

geotechnical work.


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FIELD MANUAL

14

Table 2-2.Useful conversion factorsmetric and English units (inch-pound)

To convert units in column 1 to units in column 4, multiply column 1 by the factor in column 2.

To convert units in column 4 to units in column 1, multiply column 4 by the factor in column 3.

Column 1 Column 2 Column 3 Column 4

Length

inch (in) 2.540 X 10 1 3.937 X 10-2 millimeter (mm)

hundredths of feet 3.048 X 102 3.281 X 10 -3 millimeter (mm)

foot (ft) 3.048 X 10 -1 3.281 meter (m)

mile (mi) 1.6093 6.2137 X 10-1 kilometer (km)

Area

square inch (in2) 6.4516 X 10-4 1.550 X 10-3 square meter (m2)

square foot (ft2) 9.2903 X 10 -2 1.0764 X 101 square meter (m2)

acre 4.0469 X 10 -1 2.4711 hectare

square mile (mi2) 0.386 X 10 -2 259.0 hectares

Volume

cubic inch (in3) 1.6387 X 10-2 6.102 X 10-2 cubic centimeter (cm2)

cubic feet (ft3) 2.8317 X 10-2 3.5315 x 101 cubic meter (m3)

cubic yard (yd3) 7.6455 X 101 1.3079 cubic meter (ms)

cubic feet (ft3) 7.4805 1.3368 x 10-1 gallon (gal)

gallon (gal) 3.7854 2.6417 X 10-1 liter (L)

acre-feet (acre-ft) 1.2335 X 103 8.1071 X 10 -4 cubic meter (m3)

Flow

gallon per minute (gal/min) 6.309 X 10-2 1.5850 X 101 liter per second (L/s)

cubic foot per second (ft3/s) 4.4883 X 102 2.228 X 10-3 gallons per minute (gal/min)

1.9835 5.0417 X 10-1 acre-feet per day (acre-ft/d)

cubic foot per second (ft3/s) 7.2398 X 102 1.3813 X 10-3 acre-feet per year (acre-ft/yr)

2.8317 X 10-2 3.531 X 101 cubic meters per second (m3/s)

8.93 X 105 1.119 X 10-6 cubic meters per year (m3/yr)

Permeability

k, feet/year 9.651 X 10-7 1.035 X 106 k, centimeter per second

(cm/sec)

Density

pound-mass per cubic foot 1.6018 X 101 6.2429 X 10-2 kilogram per cubic meter

(lb/ft3) (kg/m3)

Unit Weight

pound force per cubic foot 0.157 6.366 kilonewton per cubic meter(lb/ft3) (kN/m3)

Pressure

pounds per square inch (psi) 7.03 X 10-2 1.4223 X 101 kilogram per square

centimeter (kg/cm3)

6.8948 0.145 kiloPascal (kPa)

Force

ton 8.89644 1.12405 X 10-1 kilonewton (kN)

pound-force 4.4482 X 10-3 224.8096 kilonewton (kN)

Temperature

EC = 5/9 (EF - 32 E) EF = (9/5 EC) + 32 E

GroutingMetric bag cement per meter 3.0 0.33 U.S. bag cement per foot

Water:cement ratio 0.7 1.4 water:cement ratio by weight

by volume

pounds per square inch 0.2296 4.3554 kilogram per square centi-

per foot meter per meter (kg/cm2/m)

k, feet/year 0.1 10 Lugeon


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TERMINOLOGY

15

BIBLIOGRAPHY

[1] The Glossary of Geology, 4th edition, American

Geologic Institute, Alexandria, VA, 1997.

[2] The American Association of Petroleum Geologists

Bulletin, v. 67, No. 5, pp. 841-875, May 1983.

[3] Bureau of Reclamation,Earth Manual, 3rd edition,

part 2, Denver, CO, 1990.

[4 ] Proctor, Robert V., and Thomas L. White, "Earth

Tunneling with Steel Supports," Commercial

Shearing, Inc., 1775 Logan Avenue, Youngstown, OH

44501, 1977.


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35/449

Chapter 3

ENGINEERING CLASSIFICATION

AND DESCRIPTION OF SOIL

General

Application

Soil investigations conducted for engineering purposes

t ha t use test pits, t renches, a uger a nd dr ill holes, or ot her

explora tory meth ods a nd surfa ce sam pling a nd m a ppingare logged and described according to the Unified Soil

Cla ssif ica tion S yst em (U SC S) a s present ed in B ureau of

Recla ma t ion (Recla ma tion) sta nda rds U S B R 5000 [1] a nd

5005 [2]. Also, bedr ock ma t eria ls w ith t he engin eering

properties of soils are described using these standards

(cha pter 2). The Recla ma t ion sta nda rds a re consist ent

w ith t he America n S ociet y for Testin g Ma t eria ls (AS TM)

D esigna t ion D 2487 a nd 2488 on t he U S C S syst em [3,4].

Descriptive criteria and terminology presented are

prima rily for t he visua l classi f ica tion a nd ma nua l tests .

The ident ifica t ion port ion of t hese meth ods in a ssign ing

group symbols is l imited to soil particles smaller than

3 inches (in) (75 millimeters [mm]) and to naturally

occurr ing soils. P rovisions a re a lso ma de t o estima t e t he

percenta ges of cobbles a nd boulders by volume. Thisdescriptive system may also be applied to shale, shells,

crushed rock, and other materials if done according to

criteria est a blished in th is sect ion. C ha pter 11 a ddr esses

t he logging form a t a nd criteria for describing soil in t est

pits, t renches, a uger holes, a nd d rill hole logs.

All investiga t ions a ssocia t ed wit h la nd cla ssifica t ion forirriga t ion suita bility , da t a collect ion, a na lyses of soil

and substratum materia ls rela ted to drainage inves-

t igat ions, a nd Quat erna ry s tra t igraphy (e.g ., faul t a nd

pa leoflood st udies) a re logged a nd described using t he


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FIELD MANUAL

18

U .S. D epa rt ment of Agricultur e terminology outlined in

appendix I to Agr i cul tu r e H and book N o. 436 (Soi l

Taxonomy), da t ed D ecember 1975 [5].

All soil classification descriptions for particle sizes less

t ha n No. 4 sieve size a re t o be in m etric units.

Performing Tests and Obtaining Descriptive

Information

The U S C S g roups soils a ccord ing t o pot ent ia l engin eering

beha vior. The descriptive inform a t ion a ssists w ith esti-mating engineering properties such as shear strength,

compr essibility , a nd perm ea bilit y. These guidelines ca n

be used not only for ident ifica t ion of soils in th e field but

a lso in t he office, la bora t ory , or w herever soil sa mples a re

inspect ed a nd described.

Laboratory classification of soils [1] is not alwaysrequ ired but sh ould be perform ed a s necessa ry a nd can be

used a s a check of visua l-ma nu a l met hods. The descrip-

tors obtained from visual-manual inspection provide

valuable information not obtainable from laboratory

testing. Visual-manual inspection is always required.

The visual-manual method has particular value in

ident ifying a nd gr ouping simila r soil sa mples so t ha t only

a minimum num ber of la bora tory t ests a re required for

posit ive soil cla ssifica t ion. The a bilit y t o ident ify a nd

describe soils corr ect ly is lea rn ed more rea dily und er th e

guida nce of experienced personnel, but ca n be a cq uired by

compa ring la bora t ory t est r esult s for t ypica l soils of each

ty pe w ith their visua l a nd ma nua l cha ra cterist ics. When

identifying and describing soil samples from an area or

project , a ll t he procedures need not be follow ed. S imila rsoils m a y be gr ouped t ogether; for exa mple, one sa mple

should be ident ified a nd described complet ely, w ith t he

others identified as similar based on performing only a

few of the identification and descriptive procedures.


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SOIL

19

D escriptive inform a t ion sh ould be evalua t ed a nd r eport ed

on every sa mple.

The sa mple used for cla ssifica t ion m ust be representa t ive

of the s tra tum and be obtained by an appropriate ac-

cept ed or st a nda rd procedure. The origin of the ma t erial

mu st be corr ect ly ident ified. The origin descript ion ma y

be a boring n umber a nd d ept h a nd/or sa mple num ber, a

geologic stratum, a pedologic horizon, or a location

description with respect to a permanent monument, a

grid system, or a sta t ion num ber a nd offset .

Terminology for Soils

D efinitions for soil cla ssifica t ion a nd description a re in

accordance with USBR 3900 Standard Definit ions of

Terms a nd S ym bols Rela t ing t o S oil Mecha nics [6]:

Cobbles and boulderspa rt icles r eta ined on a 3-inch(75-mm ) U .S . St a nd a rd sieve. The follow ing t erminology

distingu ishes betw een cobbles a nd boulders:

Cobblesparticles of rock that will pass a 12-in

(300-mm ) sq ua re opening a nd be ret a ined on a 3-in

(75-mm) sieve.

Bouldersparticles of rock that will not pass a12-in (300-mm) sq ua re opening .

Gravelpa rt icles of rock t ha t w ill pa ss a 3-in (75-mm )

sieve a nd is ret a ined on a No. 4 (4.75-mm ) sieve. G ra vel

is furt her subdivided a s follow s:

Coarse gravelpa sses a 3-in (75-mm ) sieve a nd isret a ined on 3/4-in (19-mm) sieve.

Fine gravelpa sses a -in (19-mm ) sieve a nd is

ret a ined on No. 4 (4.75-mm) sieve.


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FIELD MANUAL

20

Sandpa rt icles of rock t ha t w ill pa ss a No. 4 (4.75-mm )

sieve a nd is r et a ined on a No. 200 (0.075-mm or 75-micro-

met er [m]) sieve. S a nd is furt her subd ivided a s follow s:

Coarse sandpa sses No. 4 (4.75-mm) sieve a nd is

ret a ined on No. 10 (2.00-mm) sieve.

Medium sandpa sses No. 10 (2.00-mm) sieve a nd

is r et a ined on No. 40 (425-m) sieve.

Fine sandpasses No. 40 (425-m) sieve and isretained on No. 200 (0.075-mm or 75-m) sieve.

Claypa ss es a No. 200 (0.075-mm or 75-m) siev e. S oil

ha s pla st icity w i thin a ra nge of wa ter contents a nd ha s

considera ble st rengt h w hen a ir-dry . For cla ssifica t ion,

cla y is a fine-gra ined soil, or t he fine-gra ined port ion of a

soil, w ith a pla stici ty index great er tha n 4 a nd t he plot ofpla st icity ind ex versus liquid limit fa lls on or a bove the

" A" -line (figur e 3-5, la t er in t his cha pter).

Siltpa sses a No. 200 (0.075-mm or 75-m) sieve. S oilis nonplastic or very sl ightly plastic and that exhibits

l it t le or no str ength wh en a ir-dry is a si lt . For

classification, a silt is a fine-grained soil , or the fine-gra ined port ion of a soil, wit h a pla st icity index less tha n

4 or t he plot of pla st icity index versus liqu id limit fa lls

below t he " A" -line (figur e 3-5).

Organic claycla y w ith sufficient orga nic cont ent t o in-fluence t he soil propert ies is a n orga nic cla y. For cla ssifi-

ca tion, a n orga nic clay is a soil t ha t w ould be classi f ied a s

a cla y except t ha t i t s l iqu id limit va lue a fter oven-dry ing

is less than 75 percent of i ts l iquid limit value before

oven-drying.


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SOIL

21

Organic siltsilt w ith sufficient orga nic cont ent t o in-

flu-ence th e soil propert ies. For cla ssifica t ion, a n org a nic

si lt is a soil th a t w ould be classi f ied a s a si lt except th a t

its l iquid limit value after oven-drying is less than

75 percent of it s liqu id limit va lue before oven-dr yin g.

Peatma t eria l composed prima rily of veget a ble t issuesin various stages of decomposition, usually with an or-

ganic odor, a dark brown to black color, a spongy con-

sistency, and a texture ranging from fibrous to amor-

phous. Cla ssifica t ion procedures ar e not a pplied to pea t .

Classifications of Soils

Group Names and Group Symbols

The ident ifica t ion a nd n a ming of a soil ba sed on result s

of visua l an d ma nua l tests is present ed in a subsequentsect ion. S oil is given a n ident ifica t ion by a ssigning a

group sym bol(s) a nd group na me. Im port a nt informa t ion

about the soil is added to the group name by the term

" w it h " w hen a ppropria t e (figu res 3-1, 3-2, 3-3, 3-4). The

group name is modified using with to stress other

significa nt component s in th e soil.

Figure 3-2 is a flow cha rt for a ssigning ty pica l na mes a nd

gr oup sy mbols for inorga nic fine-gr a ined soils; figure 3-3

is a flow cha rt for orga nic fine-gra ined soils; figure 3-4 is

a flow cha rt for coa rs e-gra ined soils. Refer to t a bles 3-1

a nd 3-2 for t he basic group na mes wit hout modifiers. If

t he soil ha s properties w hich do not dist inctly pla ce it in


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FIELD MANUAL

22

FINE-GRAINED SOILS

Sandy BASIC

GROUP NAME

with sand

Gravelly with gravel

COARSE-GRAINED SOILS

with silt BASIC

GROUP NAME

with sand

with clay with gravel

Figure 3-1.Modifiers to basic soil group names

(for visual classification).

a specific group, bord erline sym bols ma y be used. There

is a distinction between dual symbol s a n d border l ine

symbols.

Dual Symbols.Dual symbols separated by a hyphen

a re used in la bora t ory cla ssifica t ion of soils a nd in visua lclassi f ication when soils are estimated to contain

10 percent fines. A dua l sym bol (t w o sym bols sepa ra t ed

by a hyphen, e.g. , GP-GM, SW-SC, CL-ML) should be

used to indicate that the soil has the properties of a

classi f ica tion w here tw o symbols a re required. D ua l sym-

bols are required when the soil has between 5 and

12 percent fines from la bora t ory t ests (t a ble 3-2), or fines

a re estima ted a s 10 percent by visual classi f ica tion. D ua l

symbols are also required when the l iquid l imit and

plasticity index values plot in the CL-ML area of the

pla st icity cha rt (figure 3-5, la t er in th is cha pter).


41/449

23 Figure 3-2.Flow chart for inorganic fine-grained s


42/449


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25 Figure 3-4.Flow chart for coarse-grained soils


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FIELD MANUAL

26

Ta ble 3-1.B a sic group na mes, prima ry groups

C oa rse-gra ined soils Fine-gra ined soils

G W - Well gra ded gra velG P - P oor ly gr ad ed gr avel

G M - Si lt y gra vel

G C - C la y ey gr a vel s a n d

SW - Well graded sand

S P - P oor ly gr a ded sa n d

S M - S ilt y sa n d

S C - C la yey sa n d

C L - L ea n cla yML - S ilt

OL - Orga nic clay (on or

a bove A-line

- Orga nic silt (below A-line)

C H - F a t cla y

MH - E la st ic silt

OH - Organ ic clay (on or a bove

A-line)- Orga nic silt (below A-line)

B a sic group nameha tched a rea on P last icity Ch a rt

(La bora tory C lassifica tion)

C L-ML - S ilt y cla y

G C-G M - Si lt y , clayey gravel

S C -S M - S ilt y , cla y ey s a n d

Ta ble 3-2.B a sic group na mes, 5 t o 12 percent fines

(La bora tory Cla ssifica tion)

G W-G M - Well gra ded gra vel w it h silt

G W-G C - Well gra ded gra vel w it h cla y (if fin es =

C L-ML) Well gra ded gra vel w ith silty clayG P -G M - P oor ly gr a ded g ra v el w it h silt

G P -G C - P oor ly g rad ed g ravel w i t h clay (if fines =

CL -ML) P oorly gra ded gra vel w ith silty clay

S W-S M - Well gra ded sa nd w it h silt

SW-SC - Well graded sand wi th clay (if f ines = CL-ML)

Well gra ded sa nd w ith silty clay

S P -S M - P oorly gra ded sa nd w it h silt

SP -SC - P oor ly g rad ed sand w i t h clay (if fines = CL -ML) P oorly gra ded sa nd w ith silty cla y


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SOIL

27

Borderline Symbols.Borderline symbols are used

w hen soil propert ies indica t e th e soil is close to a noth er

cla ssifica t ion group. Tw o sym bols sepa ra t ed by a sla sh,

such a s C L/CH , S C /C L, G M/S M, C L/ML , sh ould be used

to indicate that the soil has properties that do not

dist inctly pla ce t he soil int o a s pecific gr oup. B eca use th e

visual classification of soil is based on estimates of

pa rt icle-size dist ribution a nd pla st icity cha ra ct eristics, i t

ma y be difficult t o clea rly ident ify th e soil as belonging t o

one ca t egory. To indica t e t ha t t he soil ma y fa ll int o one

of t w o possible ba sic groups, a borderline symbol ma y be

used w i th the tw o symbols separa ted by a s lash. Aborderline classification symbol should not be used

indiscrimina t ely. E very effort should be ma de first to

pla ce th e soil int o a single group. B orderline symbols ca n

also be used in laboratory classification, but less

frequently.

A borderline symbol ma y be used w hen t he percent a ge offines is visua lly est ima t ed to be betw een 45 a nd 55 per-

cent . One symbol should be for a coa rs e-gra ined soil w ith

fines a nd t he ot her for a fine-gra ined soil. For exa mple:

G M/ML , C L/S C .

A borderline symbol ma y be used w hen t he percent a ge of

sand and the percentage of gravel is estimated to be

a bout t he sa me, for exa mple, G P /S P , S C/G C , G M/S M. It

is pra ct ica lly impossible t o ha ve a soil t ha t w ould ha ve a

border line sy mbol of G W/S W. H owever, a border line

symbol may be used when the soil could be either well

gr a ded or poorly gr a ded. For exa mple: G W/G P , S W/S P .

A bord erline sym bol ma y be used w hen t he soil could be

eith er a silt or a cla y. For exa mple: CL/ML, C H /MH ,S C /S M.


46/449


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SOIL

29

S oil ident ifica t ion procedures a re ba sed on t he minu s 3-in

(75-mm) pa r t icle sizes. All plus 3-in (75-mm) pa r t icles

must be manually removed from a loose sample, or

ment a lly for a n int a ct s a mple, before cla ssifying t he soil.

E st ima t e a nd n ot e th e percent by volume of t he plus 3-in

(75-mm ) pa rt icles, bot h t he percent a ge of cobbles a nd t he

percent a ge of boulders.

Not e: B eca use t he percent a ges of t he pa rt icle-

size distribution in laboratory classification

(AS TM: D 2487) a re by dry w eight a nd th e

estimates of percentages for gravel , sand, andfines are by dry weight, the description should

state that the percentages of cobbles and

boulders are by volume, not weight, for visual

cla ssifica t ion. E st ima t ion of the volume of cob-

bles a nd boulders is not a n easy t a sk. Accura te

estim a t ing req uires experience. While exper-

ienced loggers may be able to successfullyestimate the minus 3-in fraction to within

5 percent , th e ma rgin of error could be la rg er for

oversize pa rt icles. E st ima t es ca n be confirmed

or cal ibrated with large scale f ield gradation

t ests on crit ica l project s. G iven th e la rge pos-

sible errors in these estimates, the estimates

should n ot be used a s t he sole ba sis for d esign of

processing equipment. La rge sca le gra da t ions

should be obt a ined a s pa rt of th e process pla nt

designs.

In most cases, the volume of oversize is estimated in

three size ranges, 3 to 5, 5 to 12, and 12 inches and

la rger. Cobbles a re often divided int o t w o size ra nges,

because in roller compacted fill of 6-in compacted liftt hickness, t he ma ximum size cobble is 5 inches. If t he

purpose of the investigation is not for roller compacted

fill , a single size ra nge for cobbles can be est ima t ed.


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FIELD MANUAL

30

Estimate and note the percentage by dry weight of the

gra vel, sa nd, a nd fines of th e fra ct ion of t he soil sma ller

t ha n 3 in (75-mm ). The percenta ges a re est ima t ed to t he

closest 5 percent . The percent a ges of gr a vel, sa nd , a nd

fines must add up to 100 percent, excluding trace

a mount s. The presence of a component n ot in sufficient

quantity to be considered 5 percent in the minus 3-in

(75-mm ) port ion, is indica t ed by t he term " t ra ce." For ex-

a mple: t ra ce of fines. A t ra ce is not considered in t he

t ot a l of 100 percent for t he component s.

The first step in the identification procedure is todetermine the percentages of fine-grained and coarse-

gra ined ma t eria ls in t he sa mple. The soil is fine-gra ined

if it cont a ins 50 percent or more fines . The soil is coa rs e-

grained if i t contains less than 50 percent fines.

P rocedures for t he description a nd cla ssifica t ion of t hese

t w o prelimina ry ident ifica t ion groups follow .

Procedures and Criteria for Visual Classification

of Fine-Grained Soils

Select a representative sample of the material for

examination and remove particles larger than the

No. 40 sieve (medium sa nd a nd la rger) unt il a specimen

equiva lent t o a bout a ha ndful of represent a tive ma teria l

is a va ila ble. U se t his specimen for performing t he

ident ifica t ion test s.

Identification Criteria for Fine-Grained Soils.The

t ests for ident ifying propert ies of fines a re dry strength,

dilatency, toughness, and plasticity.

1. D r y st r en g th .S elect from t he specimen enough

material to mold into a ball about 1 in (25 mm) in

diam eter. Mold or w ork the ma teria l unt i l i t ha s the

consist ency of put t y, a dding w a t er if necessar y.


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SOIL

31

From t he molded ma teria l , ma ke a t lea st t hree test

specimens. E a ch test specimen should be a ba ll of

ma teria l a bout in (12 mm) in diam eter. Allow t he

t est specimens to dry in a ir or sun, or dry by a rt ificia l

mea ns, a s long a s t he tempera t ure does not exceed

60 degrees Cent igra de (EC ). In m ost ca ses, i t w ill be

necessa ry t o prepa re specimens a nd a l low th em t o

dry over night. I f the test specimen cont a ins nat ura l

dry lumps, those th a t a re about in (12 mm) in

dia met er ma y be used in pla ce of molded ba lls. (The

process of molding and drying usually produces

higher s trengths t ha n a re found in na tura l dry lumpsof soil). Test t he st reng t h of t he dry ba lls or lumps by

crushing them between the f ingers and note the

strength as none, low, medium, high, or very high

a ccording to t he crit eria in t a ble 3-3. If na t ura l dry

lumps a re used, do not use th e results of an y of t he

lumps t ha t a re found t o cont a in par ticles of coa rse

sand .

Ta ble 3-3.Crit eria for d escribing d ry st reng t h

None The dry specimen crumbles w it h mere

pressure of ha ndling.

Low The dry specimen crumbles w it h some

finger pressure.

M ed iu m Th e d ry specimen br ea k s in t o pieces or

crum bles w ith considera ble finger

pressure.

H igh The dry specimen ca nnot be broken w it h

finger pressure. S pecimen will brea k int o

pieces betw een t humb a nd a ha rd surfa ce.

Very High The dry specimen ca nnot be broken

betw een th umb an d a ha rd surfa ce.


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SOIL

33

3. Toughness.Following completion of the

dila ta ncy test , t he specimen is sha ped into a n

elonga t ed pat a nd rolled by ha nd on a smooth surfa ce

or between the palms into a thread about c in

(3 mm ) dia met er. (If t he sa mple is too w et t o roll

easi ly, spread the sample out into a thin layer and

a llow some w a ter loss by eva pora t ion). Fold the

sa mple threa ds a nd reroll repeat edly unt i l th e threa d

crumbles a t a dia meter of a bout c in (3 mm) when

th e soil is nea r the plast ic l imit . Note the t ime

required to reroll the thread to reach the plastic

limit . Not e t he pressure requ ired t o roll t he t hr ea dnea r t he pla st ic limit . Also, note t he st rengt h of t he

t hrea d. After t he thr ea d crum bles, the pieces should

be lumped together and kneaded unti l the lump

crum bles. Not e t he t oughn ess of t he ma t erial during

kneading.

Describe the toughness of the thread and lump aslow, medium, or high according to the criteria in

table 3-5.

Ta ble 3-5.C rit eria for describing t ough ness

Low Only slight pressure is req uired to roll t he

th rea d nea r the plast ic l imit . The th rea da nd the lump are wea k and sof t .

Medium Medium pressure is required to rol l the

th rea d to nea r th e pla stic l imit . The th rea d

a nd t he lump ha ve medium sti f fness.

H igh C on sid er a ble pr essur e is r eq uir ed t o r oll t heth rea d to nea r th e pla stic l imit . The th rea d

a nd t he lump ha ve very high sti f fness.


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FIELD MANUAL

34

4 . P las t i c i t y .On t he basis of observa tions m a de

during t he toughness t est, describe t he pla st icity of

the material according to the cri teria given in

t a ble 3-6 (figur e 3-5).

Ta ble 3-6.Crit eria for describing plas t icity

Nonpla st ic A 3-mm t hread ca nnot be rolled a t a ny

w a ter content .

Low The th rea d ca n ba rely be rolled, a nd th elump ca nnot be formed w hen drier t ha n

t he pla st ic limit .

Medium The t hrea d is eas y t o roll , a nd not much

t ime is required t o rea ch t he pla st ic limit .

The t hr ead ca nnot be rerolled a fter

rea ching th e pla st ic limit . The lump

crumbles w hen drier t ha n t he plast ic

limit.

H igh I t t a kes considera ble t ime rolling a nd

knea ding to rea ch th e pla st ic limit . The

th rea d ca n be rolled severa l t imes a fter

rea ching th e pla st ic limit . The lump ca n

be form ed wit hout crum bling w hen drierth a n th e pla stic l imit .

After the dry strength, di latency, toughness, and

plasticity tests have been performed, decide on

whether the soil is an organic or an inorganic fine-

gra ined soil.


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35 Figure 3-5.Plasticity chart.


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FIELD MANUAL

36

Identification of Inorganic Fine-Grained Soils.Classify the soils using the results of the manual tests

a nd t he ident ifying crit eria show n in t a ble 3-7. P ossible

inorga nic soils include lea n cla y (C L), fa t cla y (C H ), silt

(ML), a nd ela st ic silt (MH ). The propert ies of a n ela st ic

silt a re simila r to t hose for a lea n cla y. H ow ever, the silt

w ill dry q uickly on th e ha nd a nd ha ve a smooth , silky feel

w hen dry. S ome soils wh ich cla ssify a s MH a ccording to

t he field cla ssifica t ion crit eria a re difficult to distingu ish

from lean clay s, CL . I t m a y be necessa ry to perform

la bora t ory t esting t o ensure proper cla ssifica t ion.

Ta ble 3-7.Ident ifica t ion of inorga nic fine-gr a ined

soils from ma nua l tests

Group

symbol

Dry

st rengt h D ila t a ncy Toughness

ML None t o low S low t o

rapid

Low or th read

cannot be formed

CL Medium t o high None t o slow Medium

MH Low to medium None t o slow Low t o medium

CH H igh t o very

high

None H igh

S ome soils undergo irreversible cha nges upon a ir dr ying.

These irreversible processes may cause changes in

a tt erberg limits a nd oth er index tests . E ven unsuspected

soils such as low plasticity silts may have differing

atterberg limits due to processes like disaggregation.

When t ested a t na tur a l moisture, clay par ticles cl ing t o

silt par ticles resulting in less pla st icity . When dried, t heclay disa ggregat es, ma king a f iner a nd more w ell gra ded

mix of pa rt icles w ith increa sed pla st icity.


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SOIL

37

For foundation studies of existing or new structures,

na tur a l moisture a t terberg l imits a re preferred beca use

th e in-pla ce ma teria l w ill rema in moist . Na tur a l mois-

tur e a t terberg limits a re especial ly import a nt in cri t ica l

studies, such as earthquake l iquefaction evaluation of

silt s. On some founda t ion stu dies, such a s for pumping

pla nt d esign, consolida tion tests w ill govern, a nd na tur a l

moistur e a tt erbergs a re not required. For borrow st udies,

soils will l ikely undergo moisture changes, and natural

moistur e a tt erberg limits a re not required unless unusua l

minera logy is encount ered.

Identification of Organic Fine-Grained Soils.I f the

soil cont a ins enough orga nic pa rt icles to influence t he soil

propert ies, cla ssify th e soil as a n or gani c soi l, OL or OH .

Orga nic soils usua lly a re da rk brow n t o bla ck a nd usua lly

ha ve a n orga nic odor. Often orga nic soils w ill cha nge

color, (bla ck to brown ) w hen exposed t o a ir. Orga nic soils

norma lly do not ha ve high toughness or pla st icity. Theth read for th e toughness test is spongy. In some ca ses,

furt her identifica t ion of orga nic soils a s orga nic silts or

orga nic cla ys, OL or OH is possible. C orrela t ions betw een

the di la tancy, dry s trength, and toughness tests wi th

laboratory tests can be made to classify organic soils in

simila r ma teria ls.

Modifiers for Fine-Grained Soil Classifications.I f

ba sed on visua l observa t ion, t he soil is est ima t ed to ha ve

15 to 25 percent sa nd a nd/or gr a vel, th e words " w ith sa nd

a nd/or gr a vel" a re a dded t o t he group na me, for exa mple,

LE AN C LAY WITH S AND , (CL); S ILT WITH S AND AND

G RAVE L (ML). Refer t o figur es 3-2 a nd 3-3. I f th e soil is

visua lly est ima t ed t o be 30 percent or more sa nd a nd /or

gra vel , the w ords "sa ndy" or " gra vel ly " a re added to thegroup na me. Add the w ord " sa ndy" i f th ere a ppear s to be

more sa nd tha n gra vel . Add the w ord "gra velly" i f th ere

appears to be more gravel than sand, for example,

S AND Y LE AN C LAY (CL); G RAVEL LY F AT CLAY (CH );


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SOIL

39

Classify the soil as a CLAYEY GRAVEL (GC) or a

C LAYEY S AND (S C ) if t he fines a re cla yey a s determ ined

by t he procedures for fine-gra ined soil ident ifica t ion.

Id entify t he soil a s a S IL TY G RAVE L (G M) or a S IL TY

S AND (S M) if the fines a re silt y a s determ ined by th e pro-

cedures for fine-gra ined soil ident ifica t ion.

If the soil is visually estimated to contain 10 percent

fines, give t he soil a dua l cla ssifica t ion us ing t w o group

sym bols. The first g roup sym bol should corr espond t o a

clea n gr a vel or sa nd (G W, G P , SW, SP ), a nd t he secondsym bol should corr espond t o a gra vel or sa nd w ith fines

(G C , G M, S C , S M). The typica l na me is the first group

symbol plus "with clay" or "with si l t " to indicate the

pla st icity cha ra ct eristics of t he fines. For exa mple,

WELL GRADED GRAVEL WITH CLAY (GW-GC);

P OORLY G RAD E D S AND WITH S IL T (S P -S M). Refer to

figure 3-4.

If t he specimen is predomina nt ly sa nd or gra vel but con-

tains an estimated 15 percent or more of the other

coarse-grained consti tuent, the words "with gravel" or

" w ith san d" a re a dded to th e group na me. For exam ple:

P OORLY G RAD E D G RAVE L WITH S AND (G P ); CL AY-

E Y S AND WITH G RAVE L (S C). Refer t o figur e 3-4.

I f t he field sa mple cont a ined a ny cobbles a nd /or boulders,

the words "with cobbles" or "with cobbles and boulders"

a re a dded to th e group na me, for exa mple, SI LTY G RA-

VE L WITH C OB B LE S (G M).

Abbreviated Soil Classification Symbols

I f spa ce is l imited, a n a bbrevia ted syst em ma y be used t o

indica t e the soil cla ssifica t ion sym bol an d na me such a s

in logs, da t a ba ses, t a bles, etc. The a bbrevia t ed syst em


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40

is not a subst itut e for t he full na me a nd descriptive infor-

ma tion but ca n be used in supplementa ry present a tions.

The a bbrevia t ed syst em consist s of th e soil cla ssifica t ion

syst em ba sed on t his cha pter, wit h prefixes a nd suffixes

a s list ed below .

P refix: s = sa ndy g = gra velly

S uffix: s = w it h sa nd g = w it h gra vel

c = w it h cobbles b = w it h bou ld er s

The soil cla ssifica t ion sym bol is enclosed in pa rent heses.

E xamples a re :

C L, sa ndy lea n cla y s(C L)

S P -S M, poorly gra ded sa nd (S P -G M)g

w i th s il t a nd gra vel

G P , poor ly gra ded gra vel w it h sa nd, (G P )scb

cobbles, a nd boulders

ML, gra velly silt w ith sa nd g(ML)sc a nd cobbles

Description of the Physical Properties of Soil

Descriptive information for classification and reporting

soil properties such a s a ngula rity , sha pe, color, m oistur e

condit ions, a nd consist ency a re present ed in t he follow ing

paragraphs .

Angularity

Angularity is a descriptor for coarse-grained materials

only. The a ng ula rit y of t he sa nd (coa rse sizes only),

gra vel, cobbles, a nd boulders, a re described a s a ngula r,


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SOIL

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suba ngula r, subrounded, or rounded a s indica ted by t he

cri teria in ta ble 3-8. A ra nge of a ngula ri ty m a y be sta ted,

such a s: sub-round ed t o round ed.

Ta ble 3-8.C rit eria for d escribing a ngu la rit y of

coa rse-gra ined pa rt icles

Angula r P a r t icles ha ve sha rp edges a nd rela t ively

pla na r sides with unpolished surfa ces.

Su bangula r P a r t i cles a r e s imila r t o angu la r d escr ipt ion

but h a ve rounded edges.

Su br ou nded P ar t i cles have nea r ly plana r s id es bu t w ell-

rounded corners and edges.

R oun ded P a r t icles h a ve sm oot hly cur ved sides a n d n o

edges.

Shape

D escribe the sha pe of t he gra vel, cobbles, a nd boulders a s

f la t , elonga ted or f la t a nd elonga ted i f th ey meet t he

criteria in ta ble 3-9. In dica t e the fra ct ion of t he pa rt icles

t ha t ha ve t he sha pe, such a s: one-t hird of gra vel pa rt icles

a re f la t . I f the ma

ENGINEERING GEOLOGY FIELD MANUAL

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