Unsaturated Soil Mechanics in Engineering Practice

The definitive guide to unsaturated soil— from the world's experts on the subject

This book builds upon and substantially updates Fredlund and Rahardjo's publication, Soil Mechanics for Unsaturated Soils, the current standard in the field of unsaturated soils. It provides readers with more thorough coverage of the state of the art of unsaturated soil behavior and better reflects the manner in which practical unsaturated soil engineering problems are solved. Retaining the fundamental physics of unsaturated soil behavior presented in the earlier book, this new publication places greater emphasis on the importance of the "soil-water characteristic curve" in solving practical engineering problems, as well as the quantification of thermal and moisture boundary conditions based on the use of weather data. Topics covered include:

• Theory to Practice of Unsaturated Soil Mechanics
• Nature and Phase Properties of Unsaturated Soil
• State Variables for Unsaturated Soils
• Measurement and Estimation of State Variables
• Soil-Water Characteristic Curves for Unsaturated Soils
• Ground Surface Moisture Flux Boundary Conditions
• Theory of Water Flow through Unsaturated Soils
• Solving Saturated/Unsaturated Water Flow Problems
• Air Flow through Unsaturated Soils
• Heat Flow Analysis for Unsaturated Soils
• Shear Strength of Unsaturated Soils
• Shear Strength Applications in Plastic and Limit Equilibrium
• Stress-Deformation Analysis for Unsaturated Soils
• Solving Stress-Deformation Problems with Unsaturated Soils
• Compressibility and Pore Pressure Parameters
• Consolidation and Swelling Processes in Unsaturated Soils

Unsaturated Soil Mechanics in Engineering Practice is essential reading for geotechnical engineers, civil engineers, and undergraduate- and graduate-level civil engineering students with a focus on soil mechanics.

H. Rahardjo is head of the Division of Infrastructure Systems and Maritime Studies at the School of Civil and Environmental Engineering at Nanyang Technological University in Singapore. He is the coauthor of Soil Mechanics for Unsaturated Soils and over 200 technical publications.

M. D. Fredlund is the President/CEO of SoilVision Systems, Canada, a geotechnical/hydrological software development and numerical modeling company.

Foreword xiii

Preface xv

Acknowledgments xvii

CHAPTER 1 Theory to Practice of Unsaturated Soil Mechanics 1

1.1 Introduction 1

1.2 Moisture and Thermal Flux Boundary Conditions 6

1.3 Determination of Unsaturated Soil Properties 8

1.4 Stages in Moving Toward Implementation 9

1.5 Need for Unsaturated Soil Mechanics 11

1.6 Partial Differential Equations in Soil Mechanics 17

1.7 Engineering Protocols for Unsaturated Soils 26

CHAPTER 2 Nature and Phase Properties of Unsaturated Soil 29

2.1 Introduction 29

2.2 Soil Classification 34

2.3 Phase Properties 48

2.4 Volume-Mass Variables 66

2.5 Soil Compaction 73

2.6 Volume-Mass Relations When Mass Is Lost from System 76

CHAPTER 3 State Variables for Unsaturated Soils 80

3.1 Introduction 80

3.2 Basis for Stress State Variables 84

3.3 Stress State Variables for Unsaturated Soils 87

3.4 Representation of Stress States 94

3.5 Equations for Mohr Circle 98

3.6 Role of Osmotic Suction 105

CHAPTER 4 Measurement and Estimation of State Variables 109

4.1 Introduction 109

4.2 Measurement of Soil Suction 109

4.3 Measurement of Total Suction 149

4.4 Measurement of Osmotic Suction 164

4.5 Measurement of In Situ Water Content 165

4.6 Estimation of Soil Suction 169

CHAPTER 5 Soil-Water Characteristic Curves for Unsaturated Soils 184

5.1 Introduction 184

5.2 Volume-Mass Constitutive Relations 190

5.3 Equations for SWCC 200

5.4 Regression Analysis on SWCC Equations 214

5.5 Hysteresis, Initialization, and Interpretation of SWCC 217

5.6 Pham and Fredlund (2011) Equation for Entire SWCC 224

5.7 Gitirana and Fredlund (2004) SWCC 231

5.8 Measurement of SWCC Using Pressure Plate Devices 234

5.9 Single-Specimen Pressure Plate Devices for Geotechnical Engineering 242

5.10 Vacuum Desiccators for High Suctions 249

5.11 Use of Chilled-Mirror or Dew-Point Method 251

5.12 Estimation of SWCC 253

5.13 Two-Point Method of Estimating SWCC 263

5.14 Correlation of Fitting Parameters to Soil Properties 265

5.15 Application of SWCC 269

5.16 Guidelines and Recommendations for Engineering Practice 271

CHAPTER 6 Ground Surface Moisture Flux Boundary Conditions 273

6.1 Introduction 273

6.2 Climatic Classification for a Site 274

6.3 Boundary Value Framework for Near-Ground-Surface Design 278

6.4 Challenges of Numerical Modeling Ground Surface Moisture Flux Conditions 321

CHAPTER 7 Theory of Water Flow through Unsaturated Soils 327

7.1 Introduction 327

7.2 Theory of Flow of Water 327

7.3 Darcy’s Law for Unsaturated Soils 331

7.4 Partial Differential Equations for Steady-State Water Flow 344

7.5 Partial Differential Equations for Transient Seepage 351

7.6 Direct Measurement of Water Flow Properties 354

CHAPTER 8 Solving Saturated/Unsaturated Water Flow Problems 375

8.1 Introduction 375

8.2 Estimation of Permeability Function 375

8.3 Application to Saturated-Unsaturated Water Flow Problems 397

8.4 Conditions under Which Matric Suction Can Be Maintained 437

CHAPTER 9 Air Flow through Unsaturated Soils 450

9.1 Introduction 450

9.2 Theory of Free Air Flow 450

9.3 Fick’s Law and Darcy’s Law for Air Flow 451

9.4 Diffusion of Air through Water 458

9.5 Other Components of Air Flow 460

9.6 Partial Differential Equations for Air Flow through Unsaturated Soils 461

9.7 Direct Measurement of Air Coefficient of Permeability 465

9.8 Direct Measurement of Air Diffusion through Water 467

9.9 Indirect Estimation of Air Flow Properties 472

9.10 Applications to Saturated-Unsaturated Air Flow Problems 480

CHAPTER 10 Heat Flow Analysis for Unsaturated Soils 487

10.1 Introduction 487

10.2 Theory of Heat Flow 488

10.3 Theory of Freezing and Thawing Soils 492

10.4 Formulation of Partial Differential Equations for Conductive Heat Flow 495

10.5 Direct Measurement of Thermal Properties 500

10.6 Estimation Procedures for Thermal Properties 505

10.7 Applications to Thermal Problems 510

10.8 One-Dimensional Heat Flow in Unfrozen and Frozen Soils 511

10.9 Two-Dimensional Heat Flow Example Involving Chilled Pipeline 511

10.10 Two-Dimensional Heat Flow Example with Surface Temperatures above and below Freezing 512

10.11 Aldrich (1956) Example of Vertical Column 516

CHAPTER 11 Shear Strength of Unsaturated Soils 520

11.1 Introduction 520

11.2 Theory of Shear Strength 520

11.3 Measurement of Shear Strength 536

11.4 Special Equipment Design Considerations 541

11.5 Triaxial Test Procedures for Unsaturated Soils 551

11.6 Interpretation of Triaxial Test Results 554

11.7 Direct Shear Tests 565

11.8 Typical Laboratory Test Results 567

11.9 Selection of Strain Rate 578

CHAPTER 12 Shear Strength Applications in Plastic and Limit Equilibrium 588

12.1 Introduction 588

12.2 Estimation of Shear Strength Functions for Unsaturated Soils 588

12.3 Application to Practical Shear Strength Problems in Geotechnical Engineering 612

12.4 Bearing Capacity 626

12.5 Slope Stability 632

12.6 Optimization Procedures to Solve for Factor of Safety 642

12.7 Application of Slope Stability Analyses 651

12.8 Hazard Assessment and Decision Analysis Related to Slope Instability 662

CHAPTER 13 Stress-Deformation Analysis for Unsaturated Soils 666

13.1 Introduction 666

13.2 Concepts of Volume Change and Deformation 670

13.3 Volume-Mass Constitutive Relations 673

13.4 Compressibility Form for Unsaturated Soil Constitutive Relations 679

13.5 Relationship Among Volumetric Deformation Coefficients 685

13.6 Pham-Fredlund Volume-Mass Constitutive Model (2011a) 693

13.7 Formulation of Partial Differential Equations for Stress-Deformation in Unsaturated Soils 713

13.8 Measurement of Stress-Deformation Properties for Unsaturated Soils 721

CHAPTER 14 Solving Stress-Deformation Problems with Unsaturated Soils 731

14.1 Introduction 731

14.2 Estimation of Stress-Deformation Properties 731

14.3 Application to Practical Stress-Deformation Problems 735

14.4 Evaluation of Stress History in Unsaturated Soils 738

14.5 One-Dimensional Formulations for Deformation Analysis for Unsaturated Soil 756

14.6 Swelling Theory Formulated in Terms of Incremental Elasticity Parameters 768

14.7 Evaluation of Elasticity Parameter Functions from Volume Change Indices 771

14.8 One-Dimensional Solution Using Incremental Elasticity Formulation 775

14.9 Two-Dimensional Solution Using Incremental Elasticity Formulation 778

14.10 Challenges in Numerically Modeling of Expansive Soil Problems 778

CHAPTER 15 Compressibility and Pore Pressure Parameters 783

15.1 Introduction 783

15.2 Coupled and Uncoupled Solutions 784

15.3 Uncoupled Undrained Loading 786

15.4 Derivation of Pore Pressure Parameters 794

15.5 Drained and Undrained Loading 796

15.6 Solutions of Pore Pressure Equations and Comparisons with Experimental Results 802

15.7 Rheological Model to Represent Relative Compressibilities of Unsaturated Soil 807

CHAPTER 16 Consolidation and Swelling Processes in Unsaturated Soils 809

16.1 Introduction 809

16.2 Stress and Seepage Uncoupled and Coupled Systems 809

16.3 Solution of Consolidation Equations Using Finite Difference Technique 817

16.4 Typical Consolidation Test Results on Unsaturated Soils 819

16.5 Dimensionless Consolidation Parameters 823

16.6 Coupled Formulations and Three-Dimensional Consolidation 825

16.7 Water, Air Flow, and Nonisothermal Systems 829

16.8 Two-Dimensional Stress-Deformation and Saturated-Unsaturated Seepage Analysis 831

16.9 Computer Simulation of Edge Lift and Edge Drop of Slabs-on-Ground 845

16.10 Theory for Simulation of Swelling Pressure Development 848

16.11 Rheological Model for Unsaturated Soils 851

APPENDIX Units and Symbols 858

References 864

Index 911

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