Principles of

Principles ofGeotech n ical E ngi neeri ngFIFTH EDITION

BRAJA M. DASCalifornia State Universitv, Sacramento

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THOIVISON LEARNING

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Library of Congress Cataloging-in-Publication Data

Das, Braja M.- e.in"i if"t of geotechnical engineering / Braja M Das'-5th cd'

D. Cm.

Iniludes bibliographical references and index'

ISBN 0-534-38742-X1. Soil mechanics. 2. Engineering geology'

TA710 .D2642001624.1'5136 - dc21

ffi

l-

Contents

7 nt Geotechnical Engineering-A Historical Perspective 1l . l Geotcchnical E,ngineering Prior to the ltJth Century I1.2 Pre-Classical Pcr iod of Soi l Mechanics (1 j00-11j6) 41.3 Classical Soi l Mechanics - Phase I (1776-1u56) 51.4 Classical Soi l Mechanics - Phase I I (18-56-1910) .51.5 Modern Soi l Mechanics 61.6 Geotcchnictrl E,nginecring Aftcr 1927 6

Refcrences I 1

4z 0r ig in of Soi l and Grain Size 132.1 Rock Cyclc and thc Origin of Soil l32.2 Soi l -Par t ic lc Size 202.3 Clay Minerals 2 l2.4 Spccil ic Gravity (G,) 282.5 Mechanical Analysis of Soil 292.6 Particle-Size Distribution Curve 362.7 Particle Shape 402.8 Summary 42

Problems 42References 44

3 Weight-Volume Belat ionships, Plastici ty,and Structure of Soi l 453.1 Weight-VolumeRelationships 453.2 Relationships Among Unit Weight, Void Ratio, Moisture Content,

and Specific Gravity 483.3 Relationships Among Unit Weight, Porosity, and Moisture Content 51

vi Contents

3.4 Various Unit-Weight Relationships 53

3.5 Relative DensitY 583.6 Consistency of Soil - Atterberg Limits

3.7 Liquid Limit (LL) 613.8 Plastic Limit (PL) 653.9 Shrinkage Limit (SL) 68

3.10 Liquidity Index and Consistency Index

3.L1 Activity 113.12 PlasticitY Chart 123.13 Soil Structure 733.14 SummarY 18Problems 78References tt I

4 Engineering Classif icat ion of Soi l 834.1 AASHTO Classification System 83

4.2 Unil ied SoilClassification System 81

4.3 Summary and Comparison Betwecn the AASHTO

and Unified SYstems 9-5

Problems 9uReferences 99

Soi l Compact ion 100

61

5

6

5.1 Compaction - General Principlcs 1(X)

5.2 Standard Proctor Test I01

5.3 Factors Affecting Compaction 104

5.4 Moclified Proctor Test 101

5.5 Structure of Compacted Clay Soil I I0

5.6 Fie ld ComPact ion 113

5.7 Specifications for Field Compaction I l6

5.8 Determination of Field Unit Weight of Compaction 120

5.9 Compaction of Organic Soil and Waste Materials 125

5.10 SpecialCompactionTcchniques 129

5.11 Summary and General Comments 135

Problems 135Referenccs 131

Permeabi l i ty 1396.1 Bernoulli 's Equation 1396.2 DarcY's Law 1416.3 Hydraulic ConductivitY 7436.4 Laboratory Determination of Hydraulic Conductivity 145

6.5 Empirical Relations for Hydraulic Conductivity 150

Contents

6.6 Directional Variation of permeability 15563 Equivalent Hydrauric conductivity in Stratified Soil 15i6.8 Hydraulic Conductivity of Compacted Clayey Soils 1606'9 considerations for Hydrauric Conductivity oi clayey Soirs

in Field Compaction l626.10 Moisture content - Unit weight criteria for clay Liner construction9.11

Permeabil ity Test in the Field by pumping from Wells t649'12 In situ Hydraulic concluctivity of compactecl cray Soirs 16g6.13 Summary and General Comments 172Problems 172References 176

Seepage 1787.1 Laplace's Equation of Continuitv l TfJ

72 Cont inui ty Equat i .n for Sorut ion of Simple Flow problems lu0

7.3 Flow Nets 1837.4 Seepage Calculation from a Flow Nct lg-57.5 Flow Nets in Anisotropic Soil 1ll97.6 Mathemerr ica l Solur ior i for Secpage l9 l7.7 Uplift pressure Under Uydrauiic.structures l9l1.8 Seepage Through an E,arth Dam on an Impervious Base 1937:9 L. casagrande's Sorution for Seepage Through an Earth Dam 195

7.10 Suntmary 1L)7Problems 197References 198

ln Situ Stresses 1gg8.1 Stresses in Saturated Soil without Seepagc lgg8.2 Stresses in Saturated Soil with Upwarrl Seepage 2048.3 Stresses in Saturated Soil with Downward S""pug" 2068.4 Seepage Force 2088.5 Use of Filters to Increase thc Factor of Safety Against Heave 2138.6 Selection of Filter Material 2148.7 Capil lary Rise in Soils 2158.8 Effective Stress in the Zone of Capil lary Rise 21u8.9 Summary and General Comments 2Ig


Stresses in a Soil Mass ZZ49.1 Normal and Shear Stresses on a plane9.2 Stress Caused by a point Load Z2g9.3 Vertical Stress Caused by a Line Load

vtl

r64

7

I

I

I

z J l

vaii Contents

9.4 Vertical Stress Caused by a Strip Load (Finite Width and

Inlinite Length) 234

9.5 Vertical Strcss Due to Embankment Loading 231

9.6 Vertical Stress Below the Center of a Uniformly Loaded

Circular Area 241g.7 Vertical Stress at Any Point below a Uniformly Loaded Circular Area 242

9.8 Vertical Stress Caused by a Rectangularly Loadcd Arca 242

9.9 Influence Chart for Vertical Pressure 251


Problems 254Rcferences 25lt

1o Compressib i l i tY of Soi l 25910.1 Contact Prcssure and Scttlemcnt Profi le 259

10.2 Rclations l 'or Immediatc Settlement Calculation 261

10.3 Improved Rclat ionship for Immediate Sct t lemenl 263

10.4 Fundanentals of Clonsolicl irt ion 268

10.5 Onc-Dimensional Laboratory Consol idat ion Tcst 211

10.6 Void Rat io-Pressurc Plots 273

10.7 Normally Consolidatcd and Ovcrconsolidated Clays 214

10.8 ElTcct 9f Disturbance rtn Voicl Ratio-Prcssure Relationship 211

10.9 Calculal. ion clf Settlenlent from Onc-Dirnensional

Pr imaryConsol idat ion 2u0

10.10 Comprcssion Indcx (C,) and Swel l Index (C,) 281

10.11 SecondaryConsol idat ionSet t lcment 2t t5

10.12 Timc Ratc of Clonsoliditt ion 287

10.13 Coelficient o[ Consolidation 292

10.14 Calculat ion of Consol idat ion Sct t lemcnt Under a Foundat ion 300

10.15 Methoil of Accclerating Clonsolidation Scttlemcnt 302

10.16 Summary and General Commcnts 304

Problems 30-5Re[erences 309

' I t Shear Strength of Soi l 311l l .1 Mohr-Coulomb Fai lure Cr i ter ion 3 l I

| | . 2 I n c l i n a t i o n o f t h e P l a n e o f F a i l u r e C a u s e d b y S h e a r 3 1 311.3 Laboratory Tests for Determination of Shear Strength Parameters 314

11.4 Direct Shear Test 3 I -5

11.5 Drainecl Direct Shear Test on Saturatcd Sand and Clay 318

11.6 General Comments on Direct Shear Test 320

11.7 Triaxial Shear Test - General 323

11.8 Consolidated-Drained Triaxial Test 324

1L.9 Consolidated-UndrainedTriaxialTest 332

11.10 Unconsolidated-UndrainedTriaxialTest 331

12

Contents

11.11 Unconfined Compression Test on Saturated Clay 33911.12 Stress Path 34011.13 Vane Shear Test 34611.14 other Methods for Determining Undrainecr Shear strensth 35011.15 Sensitivity and Thixorropv of Clay 3-5011.16 Empirical Relationships Betwecn Undrained cohesion (c,,) and Effective

Overburden Pressure (oj,) 35411.17 Shear Strength of Unsaturated Cohesive Soils 3-5611.18 Summary and General Commcnts 35i-Problcms 3-58Rcfercnces 363

Lateral Earth Pressure: At-Rest, Rankine, and coulomb 364l2.l At-Rest, Activc, and passive pressures 36412.2 Earth Pressure at Rcst 366l2-3 Earth Pressure at Rcst for partiaily Submerged Soir 36rJ12.4 Latcral Pressurc on Retzrining Walls from Surcharges _

Basccl on Theory of Elast ic i ty 3 l I12.5 Rankinc',s Theory of'Activc prcssure 31412.6 Thcory of Rankinc'.s passivc pressure 31712.7 Yiclcling of Wall of Lirnitecl Hcieht 37lJ12.8 Diagrams for Latcra l Ear th prcs.surc ' Dist r ibut i .n Asainst

Reta in ing Wal ls 38012.9 Rankine Active ancl passive prcssurc with Sloping Backfi l l 3g2

12.10 Coulomb'.s Activc prcssure 396l2. l l Graphic Solut ion for c .u lomb' .s Acl ive E,ar th pressure 39x12.12 Active Force .n Rctaining walls with E,arthquake Forces 40212.13 P,,"l-ctr t ' '-g'Soil Backfi l l 40712.14 Coulomb'.s Passive Prcssure 4ll12.15 Passive Forcc .n Reterining wails with E,arthquake Forces 41312.16 Summary and Generer l Clomments 414Problems 41-5References 419

Lateral Earth Pressure-curved Failure Surface 420Retaining Walls with Friction 420Properties of a Logarithmic Spiral 422Procedure for Determination of passive Earth pressure. p-(Cohesionless Backfi l l) 424Coefficient of Passive Earth pressure, K,, 426Passive Force on Walls with Earthquake Forces 42gBraced Cuts - General 430Determination of Active Thrust on Bracing Systems of open cutsin Granular Soil 434

13

13.113.213.3

13.413.513.6t3.7

, , [

Contents

14

13.8 Determination of Active Thrust on Bracing Systems for Cuts

in Cohesive Soil 437

L3.9 Pressure Variation for Design of Sheetings' Struts' 1n! Wates 438

t-.tO Oynamic Earth Pressure Diitribution Behind a Wall Rotating

About the ToP 441l3. l I SummarY 442Problems 442References 444

Slope Stability 44514.1 Factor of SafetY 441

14.2 Stabil ity of Infinite Slopes 448

14.3 Finite SloPes - General 453

14.4 Analysis of Finite Slopes with Plane Failure Surfaces

(Culmann's Method) 454

14.5 Analysis of plnite siop., with circular Failure Surfaces - General 457

14.6 Mass Procedure - Slopes in Homogeneous Clay Soil with d : 0 458

14.7 Mass Procedure for Stabil ity of Saturated clay Slopes (d : 0 condition)

with Earthquake Forces 463

14.8 Mass Procedure - Slopes in Homogeneous c'-<f ' Soil 466

14.9 OrdinarY Method of Slices 472

14.L0 Bishop's Simplif ied Method of Slices 476

l 4 . l l S t a b i l i t y A n a | y s i s b y M e t h o c l o f S l i c e s f o r S t e a d y S t a t c S e e p a g e 4 T ]14.12 MorgensterniMethod of Slices for Rapid Drawdown Condition 485

14.13 Cousin's Charts 4il8

14.14 Fluctuation of Factor of Safcty of Slopes in Clay Embankment

on Saturated ClaY 492


Problems 491

References 502

Soil-Bearing capacity for Shallow Foundations 503

15.1 Ultimate Soil-Bearing Capacity for Shallow Foundations 504

15.2 Terzaghi's Ultimate Bearing Capacity Equation 506

15.3 Geneial Bearing Capacity Equation 512

15.4 Effect of Ground Water Table -516

15.5 Factor of SafetY 57115.6Ul t imateLoadforSha l lowFoundat ionsUnderEccent r i cLoad52315.7 Bearing Capacity of Sand Based on Settlement 526

15.8 Plate Load Test 52815.9 Ultimate Bearing Capacity on Layered Soil 530



15

16

Contents

Landfi l l Liners and Geosynthetics 54416.1 Landfill Liners - Overview 54416.2 Geosynthetics 54516.3 Geotexti les 54516.4 Geomembranes 54816.5 Geonets 5-5016.6 Single clay Liner and Single Geomembrane Liner Systems 55116.7 Recent Advances in the Liner Systems for Landfil ls 55216.t1 Leachate Removal Systems -5-5316.9 Closure of Landfil ls -5-55

16.10 Summary and General Commcnts -556References 551

Subsoil Explorat ion 55817.l Plnnning for Soil E,xplorarion -5-5817.2 Boring Methods 56017.3 Common Sampling Methods -56317.4 Sample Disturbance -56617.5 Correlations for Standard Penetration Test -56617.6 Othcr 1n Sirrr Tcsrs -57017.7 Rock Coring 513l7.tl Soil Exploration Report -57-5

Problems 571References -57u

Answers to Selected Problems 581

Index 585

17

Preface

Principles of Geotechnicul .Lngineering, Fifth Edition is intended for introductorycourses in soils and geotechnical engineering taken by virtually all civil engineeringmaj.rs. The book als. is usefur for*prof'essionals ancLother."od"., wanting a gen_eral introduction to this important aipect of engineering. As in ito tirrt four eclit ionsof the book ( 1985, r 990; rgg4, ana tuosl, this new editi lon on".' on overview of soilpropertics and mechanics, together with coverage of l ierd practices and basic engi_neering procedures. principre"^ ,.f' Fbuntlari., Enl4ineering, Fourth Edition ( 1999), bythe same author, goes on to apply these gcncral concepts and procedures to earth,earth-supportcd, and earth-rctaining strtictures, with an emphasis on design. prin_

ciples of Geotechnical Engineering Fifth Edition provides the bact ground infor-mation nceded to support stucty in rater design-oriented .ou.r"r-o, rn professionalpractice.

Changes in the Fifth Edition

The Fifth Edition, consisting of 17 chapters, includes a number of new features thatwere incorporated in response to suggestions made by professors, students, and pro_fessionals famiriar with the earlier rl"rsions of the book. The major changes are thefollowing:

o SI units are used as the principal units throughout the text with English units inparenthesis when required.r Example problems and homework problems are in both SI and Engrish units.o chapter 1, entitred "Geotechnicar Engineering - A Historicar perspective,,,

provides a brief history of the developlent of-geotechnicar engineering fromthe early 18tr'century to the present.' chapter 4 discusses only the engineering classifications of soil (AASHTo andUnified classificarion sysrems). The textiral classification ,t;;;;r, which onryprovide a historical perspective, were deleted.' The most recent ASTM specifications for laboratory compaction of soil are in-corporated into Chapter 5.

Preface

In the previous editions of the text, permeabil ity and seepage were treated in

the same chapter. In this edition, permeabil ity is discussed in Chapter 6 and

seepage is presented in ChaPter 7.

In chapter 6 (permeabil ity), recent methods for determination of in situlty-

draulic conductivity of compact clay soils have been added.

The procedure for estimating vertical stress increase due to embankment load-

ing is included in ChaPter 9.

Chap te r l 0 p resen l s t hc compress ih i l i t y o l so i l . Thc sequence o f p resen la l i on o f '

the fopics has changed. Discussions on immediate (elastic) settlement precedes

consolidation settlement. Recently developed improved relationships for imme-

diate settlement calculation which account for the rigidity of foundations, depth

of embedment, l inear increase in the modulus ol'clasticity of soil, and the etTcct

of location of a rigicl layer at a l imited depth have been added. The hyperbola

method for estimating the cocfficient ol 'consolidation lrom laboratory test re-

sults also has been included in this chapter.

In the Fourth Edition of the text, static and clynamic lateral earth pressures

werc covered in Chapters 10 and 11, respcctively. Some rearrangement of topics

on latera l ear th pressure (Chapters 12 and 13) has been inc luded in th is edi t ion.

Static and dynamic lateral earth pressures with plane failure surfaces in soil are

treated in Chzrpter 12. Chapter l3 discusscs lateral earth prcssurcs detcrmined

with curved failure surfaccs in soils including problems with braccd cuts.

Spencer's solution for slopc stabil ity arnalysis wzrs replaced by Cousin'.s solution

in th is edi t ion (Chapter 14) .In chaptcr 1-5 (Soil Bearing capacity for Shallow Foundations), Meycrhof'.s re-

lationsirips for estimating bearing capircity of sand based on settlemcnt rcplaces

the char ts o l Peck, Hanson, and' l 'hornburn (1974). Discussions on the u l t imatc

bearing capacity of founclations on slope were deletcd since they are considered

advanCed topics. Thcories relating to the ultimate bearing capacity of layered

soi l were added (Sect ion 15.9) .

Acknowledgments

I am grateful to my wife, Janice, for typing the manuscript and preparing some of the

figures and tablcs- She has been the driving forcc in the completion of this edition of

the text .The previous four editions have been reviewedby 21 individuals; their helpful

comments and suggestions have improved the quality of the book. For their reviews

and helpful suggestions for the development of the Fifth Edition of the text, I would

like to thank the following persons: Tuncer B. Edil, University of Wisconsin - Madi-

son; Lois G. Schwarz, University of Arkansas - Fayetteville; and Raj V. Siddhalthan.

University of Nevada, Reno.And finally, many thanks are due to Publisher Bil l Stenquist and the produc-

tion staff at Brooks/Cole for the final development and production of the book'Braja M. Das

Sacramento, Califo rnia

Ahout the Author

Profbssor Braja Das receivecl his M.S. in Civil Ensi_neering from thc University of Iowa, Iowa City, aidhis Ph.D. in Georcchnical Engineer ing f rom thc Uni_vers i ty of Wisconsin, Madison. Ue lJ tne author ofscveral geotechnical engineering texts and ref.erenccbooks including princ:iples o.f GJcttechnicat| Lngineer-ing,. Principle.r of' Fountlution Engineering, trnd prin-ciples oJ Soil Dynarnics, all puUiisnea by ThomsonLearning. He has authorcd morc than 2dt) tcctrnicalpapers in the area of geotechnical engineering. Hisprimary areas of research include shIIt,rw fr;"l;_tions, earth anchors, and geosynthetics.

Professor Das has previously scrvecl on ASCE,sShal low Foundat ions Commit tee, Dcep Foundat ionsCommit tee, and Grout ing Commit tee. 'He was a lso amember crf ASCEIs editorial board lbr thc Jturnur of G\otechan.icat nngineerirg. alis the founder of t l.tc Geotechnical Engineering Division of the Iniernational Societyof offshore and Polar Engincers andias servecl as an associate editor of ISopEsInternational Journar o.f c)ff.shore antr prrar Engineering. He now serves on the edi_torial board of the journar Lowrarur rechnotogy International *t i.n is published inJapan' Recently he has been named as the co-edi tor of Geotechnical anrl GeologicalEngineering- An International Journal published by Kluwer Academic publishers

of the Netherlands' He was the chair of the committee on cr,,"-i.ur and MechanicalStabil ization of the Transportation Research Board of the Nationut R"r.u..t coun-c i l o f the Uni ted Srares (1995_2001).Dr' Das has received numerous awards for teaching excellence, incrudingthe AMoco Foundation Award, AT&T Award for Teaching Exce'ence from theAmerican Society for Ergineering Education, the Ralph Teetor Award from theSociety of Automotive Engineers,"and the Distinguish;d Ach;ement Award forTeaching Excellence from the University of ,lexas

at El paso.Since 1994, prof'essor Das has served as Dean o^f the college of Engineeringand Computer Science at California State University, Sacramento.

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