Geotechnical engineering: unsaturated and saturated soils

Geotechnical

Engineering:

Unsaturated and

Saturated Soils

Geotechnical

Engineering:

Unsaturated and Saturated Soils

Jean-Louis Briaud

Cover image: C Art Koenig, Photographer/Artist

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Library of Congress Cataloging-in-Publication Data:

Briaud, J.-L.

Introduction to geotechnical engineering : unsaturated and saturated soils /

Jean-Louis Briaud.

pages cm

‘‘Published simultaneously in Canada’’—Title page verso.

Includes bibliographical references and index.

ISBN 978-0-470-94856-9 (cloth : acid-free paper); 978-1-118-41574-0 (ebk.);

978-1-118-41826-0 (ebk.)

1. Geotechnical engineering–Textbooks. 2. Soil mechanics–Textbooks. I. Title.

TA705.B75 2013

624–dc23

2013004684

Printed in the United States of America

10 9 8 7 6 5 4 3 2 1

CONTENTS

Acknowledgments xxi

CHAPTER 1 Introduction 1

1.1 Why This Book? 1

1.2 Geotechnical Engineering 1

1.3 The Past and the Future 2

1.4 Some Recent and Notable Projects 2

1.5 Failures May Occur 5

1.6 Our Work Is Buried 5

1.7 Geotechnical Engineering Can Be Fun 5

1.8 Units 5

Problems 10

Problems and Solutions 11

CHAPTER 2 Engineering Geology 15

2.1 Definition 15

2.2 The Earth 15

2.3 Geologic Time 15

2.4 Rocks 17

2.5 Soils 17

2.6 Geologic Features 19

2.7 Geologic Maps 20

2.8 Groundwater 20

Problems 22

Problems and Solutions 22

CHAPTER 3 Soil Components and Weight-Volume Parameters 26

3.1 Particles, Liquid, and Gas 26

3.2 Particle Size, Shape, and Color 26

3.3 Composition of Gravel, Sand, and Silt Particles 28

3.4 Composition of Clay and Silt Particles 28

3.5 Particle Behavior 29

3.6 Soil Structure 30

3.7 Three-Phase Diagram 30

3.8 Weight-Volume Parameters 31

3.9 Measurement of the Weight-Volume Parameters 32

3.10 Solving a Weight-Volume Problem 33

Problems 34

Problems and Solutions 35

v

vi CONTENTS

CHAPTER 4 Soil Classification 46

4.1 Sieve Analysis 46

4.2 Hydrometer Analysis 47

4.3 Atterberg Limits and Other Limits 50

4.4 Classification Parameters 53

4.5 Engineering Significance of Classification

Parameters and Plasticity Chart 55

4.6 Unified Soil Classification System 55

Problems 56

Problems and Solutions 57

CHAPTER 5 Rocks 63

5.1 Rock Groups and Identification 63

5.2 Rock Mass vs. Rock Substance 63

5.3 Rock Discontinuities 66

5.4 Rock Index Properties 66

5.5 Rock Engineering Properties 67

5.6 Rock Mass Rating 68

5.7 Rock Engineering Problems 69

5.8 Permafrost 71

Problems 72

Problems and Solutions 74

CHAPTER 6 Site Investigation, Drilling, and Sampling 80

6.1 General 80

6.2 Preliminary Site Investigation 80

6.3 Number and Depth of Borings and In Situ Tests 80

6.4 Drilling 81

6.4.1 Wet Rotary Drilling Method 81

6.4.2 Hollow Stem Auger Drilling Method 82

6.5 Sampling 83

6.5.1 Sample Disturbance 83

6.5.2 Common Sampling Methods 84

6.6 Groundwater Level 85

6.7 Field Identification and Boring Logs 87

6.8 Soil Names 88

6.9 Offshore Site Investigations 89

6.9.1 Offshore Geophysical Investigations 94

6.9.2 Offshore Geotechnical Drilling 95

6.9.3 Offshore Geotechnical Sampling 99

Problems 99

Problems and Solutions 100

CHAPTER 7 In Situ Tests 104

7.1 Standard Penetration Test 104

7.2 Cone Penetration Test 107

7.3 Pressuremeter Test 111

7.4 Dilatometer Test 114

7.5 Vane Shear Test 115

CONTENTS vii

7.6 Borehole Shear Test 117

7.7 Plate Load Test 119

7.8 California Bearing Ratio Test 122

7.9 Pocket Penetrometer and Torvane Tests 122

7.10 Pocket Erodometer Test 123

7.11 Compaction Control Tests 124

7.11.1 Sand Cone Test 124

7.11.2 Rubber Balloon Test 124

7.11.3 Nuclear Density/Water Content Test 125

7.11.4 Field Oven Test 125

7.11.5 Lightweight Deflectometer Test 126

7.11.6 BCD Test 126

7.12 Hydraulic Conductivity Field Tests 127

7.12.1 Borehole Tests 127

7.12.2 Cone Penetrometer Dissipation Test 129

7.12.3 Sealed Double-Ring Infiltrometer Test 130

7.12.4 Two-Stage Borehole Permeameter Test 131

7.13 Offshore In Situ Tests 132

Problems 135

Problems and Solutions 136

CHAPTER 8 Elements of Geophysics 151

8.1 General 151

8.2 Seismic Techniques 151

8.2.1 Seismic Waves 151

8.2.2 Seismic Reflection 153

8.2.3 Seismic Refraction 154

8.2.4 Cross Hole Test, Seismic Cone Test,

and Seismic Dilatometer Test 155

8.2.5 Spectral Analysis of Surface Waves 156

8.3 Electrical Resistivity Techniques 160

8.3.1 Background on Electricity 160

8.3.2 Resistivity Tomography 160

8.4 Electromagnetic Methods 161

8.4.1 Electromagnetic Waves 161

8.4.2 Ground-Penetrating Radar 162

8.4.3 Time Domain Reflectometry 162

8.5 Remote Sensing Techniques 165

8.5.1 LIDAR 165

8.5.2 Satellite Imaging 165

Problems 166

Problems and Solutions 166

CHAPTER 9 Laboratory Tests 172

9.1 General 172

9.2 Measurements 172

9.2.1 Normal Stress or Pressure 172

9.2.2 Shear Stress 172

9.2.3 Water Compression Stress 173

9.2.4 Water Tension Stress 173

9.2.5 Normal Strain 179

viii CONTENTS

9.2.6 Shear Strain 180

9.2.7 Bender Elements 180

9.3 Compaction Test: Dry Unit Weight 181

9.3.1 Saturated Soils 181

9.3.2 Unsaturated Soils 181

9.4 Compaction Test: Soil Modulus 184

9.4.1 Saturated Soils 184

9.4.2 Unsaturated Soils 184

9.5 Consolidation Test 185

9.5.1 Saturated Soils 185

9.5.2 Unsaturated Soils 190

9.6 Swell Test 190

9.6.1 Saturated Soils 190

9.6.2 Unsaturated Soils 191

9.7 Shrink Test 192

9.7.1 Saturated Soils 192

9.7.2 Unsaturated Soils 192

9.8 Collapse Test 193

9.8.1 Saturated Soils 193

9.8.2 Unsaturated Soils 193

9.9 Direct Shear Test 193

9.9.1 Saturated Soils 193

9.9.2 Unsaturated Soils 195

9.10 Simple Shear Test 195

9.10.1 Saturated Soils 195

9.10.2 Unsaturated Soils 196

9.11 Unconfined Compression Test 196

9.11.1 Saturated Soils 196

9.11.2 Unsaturated Soils 197

9.12 Triaxial Test 198

9.12.1 Saturated Soils 198

9.12.2 Unsaturated Soils 199

9.13 Resonant Column Test 202

9.13.1 Saturated Soils 202

9.13.2 Unsaturated Soils 204

9.14 Lab Vane Test 206

9.14.1 Saturated Soils 206

9.14.2 Unsaturated Soils 206

9.15 Soil Water Retention Curve (Soil Water

Characteristic Curve) Test 206

9.15.1 Saturated Soils 206

9.15.2 Unsaturated Soils 208

9.16 Constant Head Permeameter Test 209

9.16.1 Saturated Soils 209

9.16.2 Unsaturated Soils 211

9.17 Falling Head Permeameter Test for Saturated Soils 212

9.18 Wetting Front Test for Unsaturated Soils 213

9.19 Air Permeability Test for Unsaturated Soils 214

9.20 Erosion Test 215

9.20.1 Saturated Soils 215

9.20.2 Unsaturated Soils 217

Problems 218

Problems and Solutions 221

CONTENTS ix

CHAPTER 10 Stresses, Effective Stress, Water Stress, Air Stress,

and Strains 245

10.1 General 245

10.2 Stress Vector, Normal Stress, Shear Stress,

and Stress Tensor 245

10.3 Sign Convention for Stresses and Strains 246

10.4 Calculating Stresses on Any Plane: Equilibrium

Equations for Two-Dimensional Analysis 246

10.5 Calculating Stresses on Any Plane: Mohr Circle for

Two-Dimensional Analysis 247

10.6 Mohr Circle in Three Dimensions 248

10.7 Stress Invariants 248

10.8 Displacements 249

10.9 Normal Strain, Shear Strain, and Strain Tensor 249

10.10 Cylindrical Coordinates and Spherical Coordinates 250

10.11 Stress-Strain Curves 251

10.12 Stresses in the Three Soil Phases 251

10.13 Effective Stress (Unsaturated Soils) 252

10.14 Effective Stress (Saturated Soils) 253

10.15 Area Ratio Factors α and β 253

10.16 Water Stress Profiles 254

10.17 Water Tension and Suction 255

10.17.1 Matric Suction 256

10.17.2 Contractile Skin 257

10.17.3 Osmotic Suction 258

10.17.4 Relationship between Total Suction

and Relative Humidity 258

10.17.5 Trees 260

10.18 Precision on Water Content and Water Tension 260

10.19 Stress Profile at Rest in Unsaturated Soils 260

10.20 Soil Water Retention Curve 262

10.21 Independent Stress State Variables 264

Problems 264

Problems and Solutions 267

CHAPTER 11 Problem-Solving Methods 280

11.1 General 280

11.2 Drawing to Scale as a First Step 280

11.3 Primary Laws 280

11.4 Continuum Mechanics Methods 281

11.4.1 Solving a Failure Problem: Limit

Equilibrium, Method of Characteristics,

Lower and Upper Bound Theorems 281

11.4.2 Examples of Solving a Failure Problem 281

11.4.3 Solving a Deformation Problem 283

11.4.4 Example of Solving a Deformation

Problem 283

11.4.5 Solving a Flow Problem 286

11.4.6 Example of Solving a Flow Problem 286

11.5 Numerical Simulation Methods 289

11.5.1 Finite Difference Method 289

11.5.2 Examples of Finite Difference Solutions 291

x CONTENTS

11.5.3 Finite Element Method 294

11.5.4 Example of Finite Element Solution 300

11.5.5 Boundary Element Method 304

11.5.6 Discrete Element Method 304

11.6 Probability and Risk Analysis 305

11.6.1 Background 305

11.6.2 Procedure for Probability Approach 308

11.6.3 Risk and Acceptable Risk 310

11.6.4 Example of Probability Approach 312

11.7 Regression Analysis 313

11.8 Artificial Neural Network Method 314

11.9 Dimensional Analysis 315

11.9.1 Buckingham  Theorem 315

11.9.2 Examples of Dimensional Analysis 316

11.10 Similitude Laws for Experimental Simulations 317

11.10.1 Similitude Laws 317

11.10.2 Example of Similitude Laws Application

for a Scaled Model 317

11.10.3 Example of Similitude Laws Application

for a Centrifuge Model 317

11.11 Types of Analyses (Drained–Undrained, Effective

Stress–Total Stress, Short-Term–Long-Term) 319

Problems 319

Problems and Solutions 321

CHAPTER 12 Soil Constitutive Models 345

12.1 Elasticity 345

12.1.1 Elastic Model 345

12.1.2 Example of Use of Elastic Model 346

12.2 Linear Viscoelasticity 347

12.2.1 Simple Models: Maxwell and

Kelvin-Voigt Models 347

12.2.2 General Linear Viscoelasticity 348

12.3 Plasticity 349

12.3.1 Some Yield Functions and Yield Criteria 350

12.3.2 Example of Use of Yield Criteria 351

12.3.3 Plastic Potential Function and Flow Rule 352

12.3.4 Hardening or Softening Rule 352

12.3.5 Example of Application of Plasticity

Method 353

12.4 Common Models 353

12.4.1 Duncan-Chang Hyperbolic Model 353

12.4.2 Modified Cam Clay Model 354

12.4.3 Barcelona Basic Model 355

12.4.4 Water Stress Predictions 357

Problems 357

Problems and Solutions 358

CHAPTER 13 Flow of Fluid and Gas Through Soils 370

13.1 General 370

13.2 Flow of Water in a Saturated Soil 370

13.2.1 Discharge Velocity, Seepage Velocity,

and Conservation of Mass 370

13.2.2 Heads 371

CONTENTS xi

13.2.3 Hydraulic Gradient 371

13.2.4 Darcy’s Law: The Constitutive Law 371

13.2.5 Hydraulic Conductivity 372

13.2.6 Field vs. Lab Values of Hydraulic

Conductivity 373

13.2.7 Seepage Force 373

13.2.8 Quick Sand Condition and Critical

Hydraulic Gradient 374

13.2.9 Quick Clay 375

13.2.10 Sand Liquefaction 375

13.2.11 Two-Dimensional Flow Problem 375

13.2.12 Drawing a Flow Net for Homogeneous Soil 377

13.2.13 Properties of a Flow Net for Homogeneous

Soil 379

13.2.14 Calculations Associated with Flow Nets 379

13.2.15 Flow Net for Hydraulically Anisotropic

Soil 380

13.2.16 Flow and Flow Net for Layered Soils 381

13.3 Flow of Water and Air in Unsaturated Soil 382

13.3.1 Hydraulic Conductivity for Water

and for Air 382

13.3.2 One-Dimensional Flow 384

13.3.3 Three-Dimensional Water Flow 386

13.3.4 Three-Dimensional Air Flow 387

Problems 388

Problems and Solutions 391

CHAPTER 14 Deformation Properties 401

14.1 Modulus of Deformation: General 401

14.2 Modulus: Which One? 402

14.3 Modulus: Influence of State Factors 402

14.4 Modulus: Influence of Loading Factor 403

14.5 Modulus: Differences Between Fields

of Application 405

14.6 Modulus, Modulus of Subgrade Reaction,

and Stiffness 405

14.7 Common Values of Young’s Modulus

and Poisson’s Ratio 406

14.8 Correlations with Other Tests 408

14.9 Modulus: A Comprehensive Model 408

14.10 Initial Tangent Modulus Go or Gmax 411

14.11 Reduction of Gmax with Strain: The G/Gmax Curve 412

14.12 Preconsolidation Pressure and Overconsolidation

Ratio from Consolidation Test 413

14.13 Compression Index, Recompression Index, and Sec￾ondary Compression Index from Consolidation Test 415

14.14 Time Effect from Consolidation Test 416

14.15 Modulus, Time Effect, and Cyclic Effect from Pres￾suremeter Test 418

14.16 Resilient Modulus for Pavements 419

14.17 Unsaturated Soils: Effect of Drying and Wetting on

the Modulus 420

14.18 Shrink-Swell Deformation Behavior, Shrink-Swell

Modulus 422

xii CONTENTS

14.19 Collapse Deformation Behavior 424

Problems 426

Problems and Solutions 429

CHAPTER 15 Shear Strength Properties 443

15.1 General 443

15.2 Basic Experiments 443

15.2.1 Experiment 1 443

15.2.2 Experiment 2 444

15.2.3 Experiment 3 444

15.2.4 Experiment 4 444

15.2.5 Experiment 5 444

15.2.6 Experiment 6 445

15.3 Stress-Strain Curve, Water Stress Response,

and Stress Path 445

15.4 Shear Strength Envelope 447

15.4.1 General Case 447

15.4.2 The Case of Concrete 448

15.4.3 Overconsolidated Fine-Grained Soils 448

15.4.4 Coarse-Grained Soils 448

15.5 Unsaturated Soils 449

15.6 Experimental Determination of Shear Strength (Lab

Tests, In Situ Tests) 450

15.7 Estimating Effective Stress Shear Strength

Parameters 451

15.7.1 Coarse-Grained Soils 451

15.7.2 Fine-Grained Soils 453

15.8 Undrained Shear Strength of Saturated

Fine-Grained Soils 454

15.8.1 Weak Soil Skeleton: Soft, Normally

Consolidated Soils 454

15.8.2 Strong Soil Skeleton: Overconsolidated

Soils 455

15.8.3 Rate of Loading Effect on the Undrained

Strength 456

15.9 The Ratio su/σ

ov and the SHANSEP Method 456

15.10 Undrained Shear Strength for Unsaturated Soils 458

15.11 Pore-Pressure Parameters A and B 458

15.12 Estimating Undrained Shear Strength Values 459

15.13 Residual Strength Parameters and Sensitivity 461

15.14 Strength Profiles 462

15.15 Types of Analyses 463

15.16 Transformation from Effective Stress Solution to

Undrained Strength Solution 463

Problems 464

Problems and Solutions 465

CHAPTER 16 Thermodynamics for Soil Problems 472

16.1 General 472

16.2 Definitions 472

16.3 Constitutive and Fundamental Laws 473

16.4 Heat Conduction Theory 473

CONTENTS xiii

16.5 Axisymmetric Heat Propagation 474

16.6 Thermal Properties of Soils 475

16.7 Multilayer Systems 476

16.8 Applications 477

16.9 Frozen Soils 478

Problems 479

Problems and Solutions 480

CHAPTER 17 Shallow Foundations 485

17.1 Definitions 485

17.2 Case History 485

17.3 Definitions and Design Strategy 485

17.4 Limit States, Load and Resistance Factors,

and Factor of Safety 488

17.5 General Behavior 491

17.6 Ultimate Bearing Capacity 491

17.6.1 Direct Strength Equations 491

17.6.2 Terzaghi’s Ultimate Bearing Capacity

Equation 494

17.6.3 Layered Soils 496

17.6.4 Special Loading 498

17.6.5 Ultimate Bearing Capacity of Unsaturated

Soils 499

17.7 Load Settlement Curve Approach 500

17.8 Settlement 502

17.8.1 General Behavior 502

17.8.2 Elasticity Approach for Homogeneouss

Soils 504

17.8.3 Elasticity Approach for Layered Soils 504

17.8.4 Chart Approach 506

17.8.5 General Approach 507

17.8.6 Zone of Influence 507

17.8.7 Stress Increase with Depth 508

17.8.8 Choosing a Stress-Strain Curve and Setting

Up the Calculations 510

17.8.9 Consolidation Settlement: Magnitude 510

17.8.10 Consolidation Settlement: Time Rate 511

17.8.11 Creep Settlement 511

17.8.12 Bearing Pressure Values 513

17.9 Shrink-Swell Movement 513

17.9.1 Water Content or Water Tension vs. Strain

Curve 513

17.9.2 Shrink-Swell Movement Calculation

Methods 514

17.9.3 Step-by-Step Procedure 514

17.9.4 Case History 516

17.10 Foundations on Shrink-Swell Soils 517

17.10.1 Types of Foundations on Shrink-Swell

Soils 517

17.10.2 Design Method for Stiffened Slabs

on Grade 518

17.11 Tolerable Movements 522