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Fundamentals of Soil Mechanics for Sedimentary and Residual Soils

Fundamentals of Soil Mechanics for Sedimentary and Residual Soils

Laurence D. Wesley

ISBN: 978-0-470-54905-6

Aug 2009

464 pages

Description

Introducing the first integrated coverage of sedimentary and residual soil engineering

Despite its prevalence in under-developed parts of the United States and most tropical and sub-tropical countries, residual soil is often characterized as a mere extension of conventional soil mechanics in many textbooks. Now, with the rapid growth of construction in these regions, it is essential to gain a fuller understanding of residual soils and their properties—one that's based on an integrated approach to the study of residual and sedimentary soils. One text puts this understanding well within reach: Fundamentals of Soil Mechanics for Sedimentary and Residual Soils.

The first resource to provide equal treatment of both residual and sedimentary soils and their unique engineering properties, this skill-building guide offers:

  • A concise introduction to basic soil mechanics, stress-strain behavior, testing, and design
  • In-depth coverage that spans the full scope of soil engineering, from bearing capacity and foundation design to the stability of slopes
  • A focus on concepts and principles rather than methods, helping you avoid idealized versions of soil behavior and maintain a design approach that is consistent with real soils of the natural world
  • An abundance of worked problems throughout, demonstrating in some cases that conventional design techniques applicable to sedimentary soils are not valid for residual soils
  • Numerous end-of-chapter exercises supported by an online solutions manual
  • Full chapter-ending references

Taken together, Fundamentals of Soil Mechanics for Sedimentary and Residual Soils is a comprehensive, balanced soil engineering sourcebook that will prove indispensable for practitioners and students in civil engineering, geotechnical engineering, structural engineering, and geology.

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CONTENTS

PREFACE xv

ACKNOWLEDGMENTS xix

1 SOIL FORMATION, COMPOSITION, AND BASIC CONCEPTS 1

1.1 Weathering Processes, Sedimentary and Residual Soils / 1

1.2 Clay Minerals / 3

1.3 Influence of Topography on Weathering Processes / 5

1.4 Factors Governing the Properties of Sedimentary and Residual Soils / 6

1.5 Remolded, or Destructured, Soils / 10

References / 11

2 BASIC DEFINITIONS AND PHASE RELATIONSHIPS 13

2.1 Components of Soil / 13

2.2 Phase Relationships / 14

2.3 Examples in Use of Phase Relationships / 17

2.4 Measurement of Basic Properties / 22

2.4.1 Bulk Density / 22

2.4.2 Water Content / 22

2.4.3 Solid Density and Specific Gravity / 22

Exercises / 24

3 BASIC INDEX TESTS, SOIL CLASSIFICATION AND DESCRIPTION 27

3.1 General / 27

3.1.1 Gravel and Sand / 27

3.1.2 Clay / 28

3.1.3 Silt / 28

3.2 Particle Size and Its Role in Influencing Properties / 28

3.2.1 Measurement of Particle Size / 29

3.3 Plasticity and Atterberg Limits / 31

3.3.1 Determination of Atterberg Limits / 31

3.4 Liquidity Index of Clay and Relative Density of Sand / 35

3.5 Sensitivity, Thixotropy, and Activity of Clays / 36

3.6 Systematic Classification Systems / 37

3.6.1 Unified Soil Classification System / 38

3.6.2 Additional Notes Regarding Classification / 40

3.6.3 Description of In situ (Undisturbed) Characteristics of Soil / 42

3.7 Classification of Residual Soils / 44

3.7.1 Parent Rock / 45

3.7.2 Usefulness of Existing Systems / 45

3.7.3 Classification of Weathering Profile / 46

3.7.4 Importance of Mineralogy and Structure / 47

References / 48

4 STRESS AND PORE PRESSURE STATE IN THE GROUND 49

4.1 Vertical Stress in the Ground / 49

4.2 Pore Pressures above Water Table and Seasonal Variations / 50

4.2.1 Case A: Coarse-Grained Soils / 52

4.2.2 Case B: Low-Permeability Clays / 53

4.2.3 Case C: Medium- to High-Permeability Clays / 53

4.3 Hill Slopes, Seepage, and Pore Pressures / 55

4.4 Significance of the Water Table (or Phreatic Surface) / 56

4.5 Horizontal Stress in Ground / 57

4.6 Worked Examples / 60

4.6.1 Worked Example 1 / 60

4.6.2 Worked Example 2 / 62

References / 64

Exercises / 64

5 STRESSES IN THE GROUND FROM APPLIED LOADS 67

5.1 General / 67

5.2 Elastic Theory Solutions for Stresses Beneath Loaded Areas / 68

References / 74

Exercises / 75

6 PRINCIPLE OF EFFECTIVE STRESS 77

6.1 The Basic Principle / 77

6.2 Applied Stresses, Drained and Undrained Behavior / 80

6.3 Pore Pressure Changes Under Undrained Conditions / 81

6.4 Some Practical Implications of the Principle of Effective Stress / 83

6.4.1 Stress State on Soil Element Below Submerged Surface (Bed of Lake or Seabed) / 83

6.4.2 Force Resisting Sliding of Concrete Gravity Dam / 84

6.4.3 Influence of Rainfall on Slope Stability / 85

6.4.4 Ground Settlement Caused By Lowering Water Table / 86

References / 87

7 PERMEABILITY AND SEEPAGE 89

7.1 General / 89

7.2 Pressure, “Head,” and Total Head / 90

7.3 Darcy’s Law / 92

7.3.1 Notes on Darcy’s Law / 92

7.3.2 Note on Seepage Velocity / 92

7.4 Measurement of Permeability / 93

7.5 General Expression for Seepage in a Soil Mass / 95

7.6 Steady-State Flow, Laplace Equation, and Flow Nets / 97

7.6.1 Flow nets—Conventions Used in Their Construction / 99

7.6.2 Boundary Conditions for Flow Nets / 100

7.6.3 Methods for Solution of Flow Nets / 101

7.6.4 Basic Requirements of Flow Net and Rules for Hand Sketching Flow Nets / 102

7.6.5 Use of Flow Nets for Practical Purposes / 103

7.7 Critical Hydraulic Gradient (and “Quicksand”) / 104

7.7.1 Quicksand / 106

7.7.2 Worked Example / 106

7.8 Unconfined Flow Nets and Approximations in Conventional Formulation / 108

7.9 Use of Filters in Designed Structures / 109

7.10 Vertical Flow Through Single Layers and Multilayers / 111

7.11 Note on Groundwater Studies and Groundwater Mechanics / 113

7.12 Flow into Excavations, Drains, and Wells / 115

References / 117

Exercises / 117

8 COMPRESSIBILITY, CONSOLIDATION, AND SETTLEMENT 121

8.1 General Concepts / 121

8.2 Estimation of Settlement Using Elasticity Theory / 122

8.2.1 Drained and Undrained Behavior / 123

8.2.2 Limitations of Elasticity Theory / 124

8.3 Estimation of Settlement Assuming 1-D Behavior / 124

8.4 Immediate (“Elastic”) Settlement and Long-Term (Consolidation) Settlement / 126

8.4.1 Immediate and Consolidation Settlement in Sands / 126

8.4.2 Immediate and Consolidation Settlement in Clays / 126

8.5 Consolidation Behavior of Clays (and Silts) / 129

8.5.1 Odometer Test / 129

8.5.2 Consolidation Characteristics—Magnitude / 130

8.5.3 Consolidation Behavior–Time Rate / 142

8.6 Estimation of Settlement from Odometer Test Results / 154

8.6.1 Settlement of a Building Foundation / 154

8.6.2 Settlement of Fill on Soft Clay / 160

8.7 Approximations and Uncertainties in Settlement Estimates Based on Odometer Tests / 165

8.7.1 Interpretation of Void Ratio–Stress Curves and Sample Disturbance / 165

8.7.2 Assumptions Regarding Pore Pressure State / 167

8.7.3 Lateral Deformation / 168

8.7.4 Submergence of Fill Loads / 168

8.7.5 Use of Terzaghi Theory of Consolidation for Nonlinear Soils / 168

8.7.6 Influence of Inadequate Data on Actual Soil Conditions / 169

8.8 Allowable Settlement / 170

8.8.1 Total (or Absolute) Settlement / 170

8.8.2 Relative Movement between Structure and Surrounding Ground / 170

8.8.3 Differential Settlement of Buildings / 170

8.9 Radial Flow and Sand (or “Wick”) Drains / 172

8.9.1 Theory for Design of Sand and Wick Drains / 173

8.10 Settlement of Foundations on Sand / 174

8.10.1 Schmertman Method Using Static Cone Penetrometer Results / 175

8.10.2 Burland and Burbidge Method / 176

8.10.3 Worked Example / 178

References / 181

Exercises / 182

9 SHEAR STRENGTH OF SOILS 185

9.1 Basic Concepts and Principles / 185

9.1.1 General Expression for Shear Strength / 186

9.1.2 Undrained Shear Strength (su ) / 187

9.1.3 Relationship between Strength in Terms of Effective Stress and Undrained Strength / 187

9.2 Measurement of Shear Strength / 190

9.2.1 Direct Shear Test (or Shear Box Test) / 190

9.2.2 Triaxial Test / 191

9.2.3 Mohr’s Circle of Stress / 193

9.2.4 Use of Mohr’s Circle for Plotting Triaxial Test Results / 195

9.2.5 Soil Behavior in Consolidated Undrained and Drained Tests / 197

9.2.6 Area Correction in Triaxial Tests / 199

9.2.7 Failure Criteria in Terms of Principal Stresses / 200

9.2.8 Determination of Angle of Failure Plane / 201

9.2.9 Worked Example / 201

9.3 Practical Use of Undrained Strength and Effective Strength Parameters / 203

9.4 Shear Strength and Deformation Behavior of Sand / 204

9.5 Residual Strength of Clays / 206

9.5.1 Measurement of Residual Strength / 208

9.6 Stress Path Concept / 209

9.7 Pore Pressure Parameters A and B / 211

9.8 Shear Strength and Deformation Behavior of Clay / 212

9.8.1 Behavior of Fully Remolded Clay / 212

9.8.2 Behavior of Undisturbed Sedimentary Clays / 214

9.8.3 Behavior of Residual Soils / 221

9.8.4 Failure Criterion and Determination of c_ and φ from Consolidated Undrained Tests / 224

9.9 Typical Values of Effective Strength Parameters for Clays and Silts and Correlations with Other Properties / 225

9.10 Undrained Strength of Undisturbed and Remolded Soils / 228

9.10.1 Sedimentary Clays / 228

9.10.2 Remolded Soils / 230

9.10.3 Residual Soils / 231

9.11 Measurement of Undrained Shear Strength / 232

9.11.1 Unconfined Compression test / 232

9.11.2 Vane Test / 232

References / 232

Exercises / 233

10 SITE INVESTIGATIONS, FIELD TESTING, AND PARAMTER CORRELATIONS 235

10.1 Overview / 235

10.2 Drilling / 235

10.2.1 Hand Auguring / 236

10.2.2 Machine Drilling / 236

10.2.3 Continuous Coring with Single-Tube Core Barrel (Also Known as Open Barrel) / 238

10.2.4 Rotary Drilling Using Core Barrels / 238

10.2.5 Wash Drilling / 239

10.2.6 Percussion Boring / 239

10.3 Undisturbed Sampling Using Sample Tubes / 239

10.4 Block Sampling / 241

10.5 Investigation Pits (or Test Pits) / 242

10.6 In Situ Testing / 242

10.6.1 Limitations of Drilling and Undisturbed Sampling / 242

10.6.2 Standard Penetration Test (Dynamic Test) / 243

10.6.3 Dutch Static Cone Penetration Test CPT / 246

10.6.4 Shear Vane Test / 249

10.7 Correlations between In Situ Test Results and Soil Properties / 250

10.7.1 SPT N Values and CPT Values / 250

10.7.2 Undrained Shear Strength of Clay / 251

10.7.3 Relative Density of Sand / 252

10.7.4 Stiffness Modulus of Sand / 253

References / 254

11 STABILITY CONCEPTS AND FAILURE MECHANISMS 257

11.1 Basic Concepts / 257

11.2 Stability of Slopes / 259

11.3 Bearing Capacity / 261

11.4 Retaining Walls / 262

11.5 Further Observations / 264

11.5.1 Safety Factors, Load Factors, and Strength Reduction Factors / 264

11.5.2 Questions of Deformation Versus Stability / 264

References / 265

12 BEARING CAPACITY AND FOUNDATION DESIGN 267

12.1 Bearing Capacity / 267

12.1.1 Bearing Capacity in Terms of Effective Stress / 270

12.1.2 Bearing Capacity in Terms of Total Stress (Undrained Behavior) / 270

12.1.3 Eccentric and Inclined Loads / 270

12.2 Shallow Foundations on Clay / 272

12.2.1 Use of Undrained Shear Strength / 272

12.2.2 Application of Factor of Safety / 272

12.2.3 Bearing Capacity Versus Settlement Tolerance in Design of Foundations / 273

12.2.4 Worked Examples / 274

12.3 Shallow Foundations on Sand / 276

12.3.1 Use of Bearing Capacity Theory / 276

12.3.2 Empirical Methods for Foundations on Sand / 277

12.4 Pile Foundations / 278

12.4.1 Basic Concepts and Pile Types / 278

12.4.2 Pile-Bearing Capacity—Basic Formula and Methods of Estimation / 281

12.4.3 Bearing Capacity of Piles in Clay / 282

12.4.4 Bearing Capacity of Piles in Sand / 285

12.4.5 Pile Group Behavior / 286

12.4.6 Lateral Load Capacity of Piles / 289

References / 303

Exercises / 304

13 EARTH PRESSURE AND RETAINING WALLS 307

13.1 Coulomb Wedge Analysis / 307

13.2 At-Rest Pressure, Active Pressure, Passive Pressure, and Associated Deformations / 312

13.3 Rankine Earth Pressures / 312

13.4 Influence of Wall Friction / 316

13.5 Earth Pressure Coefficients / 316

13.6 Total Stress Analysis / 317

13.7 Maximum Height of Unsupported Vertical Banks or Cuts / 317

13.8 Construction Factors Influencing Earth Pressures on Retaining Walls / 319

13.9 Propped (Strutted) Trenches / 321

13.10 Retaining-Wall Design Example / 322

13.11 Sheet Pile (and Similar) Retaining Walls / 329

13.11.1 FreeStanding and Propped Cantilever Walls / 329

13.12 Reinforced-Earth Walls / 337

13.12.1 Concept and General Behavior / 337

13.12.2 Reinforcement Types / 338

13.12.3 Basic Design Procedures / 339

13.12.4 Other Matters / 349

References / 351

Exercises / 351

14 STABILITY OF SLOPES 355

14.1 Introduction / 355

14.2 Analysis Using Circular Arc Failure Surfaces / 357

14.2.1 Circular Arc Analysis Using Total Stresses / 359

14.2.2 Circular Arc Analysis in Terms of Effective Stresses / 360

14.2.3 Example Calculation Using Bishop Method / 362

14.2.4 Bishop’s Method for Submerged Slopes / 363

14.3 Stability Analysis of Infinite Slopes / 366

14.4 Short- and Long-Term Stability of Built Slopes / 368

14.4.1 Excavated Slopes / 369

14.4.2 Embankments on Soft Clays / 371

14.5 Stability Analysis for Earth Dams / 377

14.5.1 Estimation of Pore-Water Pressures During or at End of Construction / 377

14.5.2 Full-Reservoir Steady-State Seepage Condition / 379

14.5.3 Rapid Drawdown Pore Pressures / 380

14.6 Influence of Climate and Weather on Stability of Slopes / 381

14.7 Stability Analysis Using Noncircular Failure Surfaces / 385

References / 387

Exercises / 387

15 SOIL COMPACTION 391

15.1 Earthworks and Soil Compaction / 391

15.2 Compaction Behavior of Soils / 391

15.3 Control of Compaction / 397

15.3.1 Traditional Method of Compaction Control / 397

15.3.2 Alternative Compaction Control Based on Undrained Shear Strength and Air Voids / 397

15.4 Difficulties in Compacting Clays / 401

15.4.1 Soils Considerably Wetter Than Optimum Water Content / 401

15.4.2 Soils That Soften During Compaction / 401

15.5 Compaction of Granular and Non-Plastic Materials / 402

References / 404

16 SPECIAL SOIL TYPES 405

16.1 General Comments / 405

16.2 Partially Saturated Soils / 406

16.2.1 Occurrence / 406

16.2.2 Measurements of Degree of Saturation / 407

16.2.3 Mechanics of Partially Saturated Soils / 408

16.3 Expansive or Swelling Clays / 415

16.3.1 Basic Concepts of Expansive Behavior / 415

16.3.2 Estimation of Swelling Pressure and Swell Magnitude / 416

16.3.3 Estimation of Swell Magnitude / 420

16.4 Collapsing Soils / 421

References / 424

INDEX 425

“Moreover, the inclusion of theory, measurement techniques and exercises at the end of each chapter provides a comprehensive teaching resource. For a soil scientist beginning to learn about soil mechanics, this textbook would be a very good choice.”  (European Journal of Soil Science, 1 August 2010)

""Designed for practitioners and students in civil engineering, geotechnical engineering, structural engineering, and geology, his text is the first to provide an equal and integrated coverage of sedimentary and residual soils and their unique engineering properties."" (Book News, December 2009)