Analysis and Design of Shallow and Deep Foundations

Preface xvii

Acknowledgments xxi

Symbols and Notations xxiii

1 Introduction 1

1.1 Historical Use of Foundations 1

1.2 Kinds of Foundations and their Uses 1

1.2.1 Spread Footings and Mats 1

1.2.2 Deep Foundations 4

1.2.3 Hybrid Foundations 7

1.3 Concepts in Design 7

1.3.1 Visit the Site 7

1.3.2 Obtain Information on Geology at Site 7

1.3.3 Obtain Information on Magnitude and Nature of Loads on Foundation 8

1.3.4 Obtain Information on Properties of Soil at Site 8

1.3.5 Consider Long-Term Effects 9

1.3.6 Pay Attention to Analysis 9

1.3.7 Provide Recommendations for Tests of Deep Foundations 9

1.3.8 Observe the Behavior of the Foundation of a Completed Structure 10

Problems 10

2 Engineering Geology 11

2.1 Introduction 11

2.2 Nature of Soil Affected by Geologic Processes 12

2.2.1 Nature of Transported Soil 12

2.2.2 Weathering and Residual Soil 14

2.2.3 Nature of Soil Affected by Volcanic Processes 14

2.2.4 Nature of Glaciated Soil 15

2.2.5 Karst Geology 16

2.3 Available Data on Regions in the United States 16

2.4 U.S. Geological Survey and State Agencies 17

2.5 Examples of the Application of Engineering Geology 18

2.6 Site Visit 19

Problems 19

3 Fundamentals of Soil Mechanics 21

3.1 Introduction 21

3.2 Data Needed for the Design of Foundations 21

3.2.1 Soil and Rock Classification 22

3.2.2 Position of the Water Table 22

3.2.3 Shear Strength and Density 23

3.2.4 Deformability Characteristics 23

3.2.5 Prediction of Changes in Conditions and the Environment 24

3.3 Nature of Soil 24

3.3.1 Grain-Size Distribution 24

3.3.2 Types of Soil and Rock 26

3.3.3 Mineralogy of Common Geologic Materials 26

3.3.4 Water Content and Void Ratio 30

3.3.5 Saturation of Soil 31

3.3.6 Weight–Volume Relationships 31

3.3.7 Atterberg Limits and the Unified Soils Classification System 34

3.4 Concept of Effective Stress 37

3.4.1 Laboratory Tests for Consolidation of Soils 39

3.4.2 Spring and Piston Model of Consolidation 42

3.4.3 Determination of Initial Total Stresses 45

3.4.4 Calculation of Total and Effective Stresses 47

3.4.5 The Role of Effective Stress in Soil Mechanics 49

3.5 Analysis of Consolidation and Settlement 49

3.5.1 Time Rates of Settlement 49

3.5.2 One-Dimensional Consolidation Testing 57

3.5.3 The Consolidation Curve 64

3.5.4 Calculation of Total Settlement 67

3.5.5 Calculation of Settlement Due to Consolidation 68

3.5.6 Reconstruction of the Field Consolidation Curve 69

3.5.7 Effects of Sample Disturbance on Consolidation Properties 73

3.5.8 Correlation of Consolidation Indices with Index Tests 78

3.5.9 Comments on Accuracy of Settlement Computations 80

3.6 Shear Strength of Soils 81

3.6.1 Introduction 81

3.6.2 Friction Between Two Surfaces in Contact 81

3.6.3 Direct Shear Testing 84

3.6.4 Triaxial Shear Testing 84

3.6.5 Drained Triaxial Tests on Sand 89

3.6.6 Triaxial Shear Testing of Saturated Clays 92

3.6.7 The SHANSEP Method 119

3.6.8 Other Types of Shear Testing for Soils 122

3.6.9 Selection of the Appropriate Testing Method 123

Problems 124

4 Investigation of Subsurface Conditions 134

4.1 Introduction 134

4.2 Methods of Advancing Borings 136

4.2.1 Wash-Boring Technique 136

4.2.2 Continuous-Flight Auger with Hollow Core 137

4.3 Methods of Sampling 139

4.3.1 Introduction 139

4.3.2 Sampling with Thin-Walled Tubes 139

4.3.3 Sampling with Thick-Walled Tubes 142

4.3.4 Sampling Rock 142

4.4 In Situ Testing of Soil 144

4.4.1 Cone Penetrometer and Piezometer-Cone Penetrometer 144

4.4.2 Vane Shear Device 146

4.4.3 Pressuremeter 148

4.5 Boring Report 152

4.6 Subsurface Investigations for Offshore Structures 153

Problems 155

5 Principal Types of Foundations 158

5.1 Shallow Foundations 158

5.2 Deep Foundations 160

5.2.1 Introduction 160

5.2.2 Driven Piles with Impact Hammer 160

5.2.3 Drilled Shafts 162

5.2.4 Augercast Piles 168

5.2.5 GeoJet Piles 170

5.2.6 Micropiles 172

5.3 Caissons 172

5.4 Hybrid Foundation 173

Problems 175

6 Designing Stable Foundations 176

6.1 Introduction 176

6.2 Total and Differential Settlement 177

6.3 Allowable Settlement of Structures 178

6.3.1 Tolerance of Buildings to Settlement 178

6.3.2 Exceptional Case of Settlement 178

6.3.3 Problems in Proving Settlement 180

6.4 Soil Investigations Appropriate to Design 180

6.4.1 Planning 180

6.4.2 Favorable Profiles 181

6.4.3 Soils with Special Characteristics 181

6.4.4 Calcareous Soil 182

6.5 Use of Valid Analytical Methods 186

6.5.1 Oil Tank in Norway 187

6.5.2 Transcona Elevator in Canada 187

6.5.3 Bearing Piles in China 188

6.6 Foundations at Unstable Slopes 189

6.6.1 Pendleton Levee 189

6.6.2 Fort Peck Dam 190

6.7 Effects of Installation on the Quality of Deep Foundations 190

6.7.1 Introduction 190

6.8 Effects of Installation of Deep Foundations on Nearby Structures 192

6.8.1 Driving Piles 192

6.9 Effects of Excavations on Nearby Structures 193

6.10 Deleterious Effects of the Environment on Foundations 194

6.11 Scour of Soil at Foundations 194

Problems 194

7 Theories of Bearing Capacity and Settlement 196

7.1 Introduction 196

7.2 Terzaghi’s Equations for Bearing Capacity 198

7.3 Revised Equations for Bearing Capacity 199

7.4 Extended Formulas for Bearing Capacity by J. Brinch Hansen 200

7.4.1 Eccentricity 203

7.4.2 Load Inclination Factors 204

7.4.3 Base and Ground Inclination 205

7.4.4 Shape Factors 205

7.4.5 Depth Effect 206

7.4.6 Depth Factors 206

7.4.7 General Formulas 208

7.4.8 Passive Earth Pressure 208

7.4.9 Soil Parameters 209

7.4.10 Example Computations 209

7.5 Equations for Computing Consolidation Settlement of Shallow Foundations on Saturated Clays 213

7.5.1 Introduction 213

7.5.2 Prediction of Total Settlement Due to Loading of Clay Below the Water Table 214

7.5.3 Prediction of Time Rate of Settlement Due to Loading of Clay Below the Water Table 219

Problems 222

8 Principles for the Design of Foundations 223

8.1 Introduction 223

8.2 Standards of Professional Conduct 223

8.2.1 Fundamental Principles 223

8.2.2 Fundamental Canons 224

8.3 Design Team 224

8.4 Codes and Standards 225

8.5 Details of the Project 225

8.6 Factor of Safety 226

8.6.1 Selection of a Global Factor of Safety 228

8.6.2 Selection of Partial Factors of Safety 229

8.7 Design Process 230

8.8 Specifications and Inspection of the Project 231

8.9 Observation of the Completed Structure 232

Problems 233

Appendix 8.1 234

9 Geotechnical Design of Shallow Foundations 235

9.1 Introduction 235

9.2 Problems with Subsidence 235

9.3 Designs to Accommodate Construction 237

9.3.1 Dewatering During Construction 237

9.3.2 Dealing with Nearby Structures 237

9.4 Shallow Foundations on Sand 238

9.4.1 Introduction 238

9.4.2 Immediate Settlement of Shallow Foundations on Sand 239

9.4.3 Bearing Capacity of Footings on Sand 244

9.4.4 Design of Rafts on Sand 247

9.5 Shallow Foundations on Clay 247

9.5.1 Settlement from Consolidation 247

9.5.2 Immediate Settlement of Shallow Foundations on Clay 251

9.5.3 Design of Shallow Foundations on Clay 253

9.5.4 Design of Rafts 255

9.6 Shallow Foundations Subjected to Vibratory Loading 255

9.7 Designs in Special Circumstances 257

9.7.1 Freezing Weather 257

9.7.2 Design of Shallow Foundations on Collapsible Soil 260

9.7.3 Design of Shallow Foundations on Expansive Clay 260

9.7.4 Design of Shallow Foundations on Layered Soil 262

9.7.5 Analysis of a Response of a Strip Footing by Finite Element Method 263

Problems 265

10 Geotechnical Design of Driven Piles Under Axial Loads 270

10.1 Comment on the Nature of the Problem 270

10.2 Methods of Computation 273

10.2.1 Behavior of Axially Loaded Piles 273

10.2.2 Geotechnical Capacity of Axially Loaded Piles 275

10.3 Basic Equation for Computing the Ultimate Geotechnical Capacity of a Single Pile 277

10.3.1 API Methods 277

10.3.2 Revised Lambda Method 284

10.3.3 U.S. Army Corps Method 286

10.3.4 FHWA Method 291

10.4 Analyzing the Load–Settlement Relationship of an Axially Loaded Pile 297

10.4.1 Methods of Analysis 297

10.4.2 Interpretation of Load-Settlement Curves 303

10.5 Investigation of Results Based on the Proposed Computation Method 306

10.6 Example Problems 307

10.6.1 Skin Friction 308

10.7 Analysis of Pile Driving 312

10.7.1 Introduction 312

10.7.2 Dynamic Formulas 313

10.7.3 Reasons for the Problems with Dynamic Formulas 314

10.7.4 Dynamic Analysis by the Wave Equation 315

10.7.5 Effects of Pile Driving 317

10.7.6 Effects of Time After Pile Driving with No Load 320

Problems 321

11 Geotechnical Design of Drilled Shafts Under Axial Loading 323

11.1 Introduction 323

11.2 Presentation of the FHWA Design Procedure 323

11.2.1 Introduction 323

11.3 Strength and Serviceability Requirements 324

11.3.1 General Requirements 324

11.3.2 Stability Analysis 324

11.3.3 Strength Requirements 324

11.4 Design Criteria 325

11.4.1 Applicability and Deviations 325

11.4.2 Loading Conditions 325

11.4.3 Allowable Stresses 325

11.5 General Computations for Axial Capacity of Individual Drilled Shafts 325

11.6 Design Equations for Axial Capacity in Compression and in Uplift 326

11.6.1 Description of Soil and Rock for Axial Capacity Computations 326

11.6.2 Design for Axial Capacity in Cohesive Soils 326

11.6.3 Design for Axial Capacity in Cohesionless Soils 334

11.6.4 Design for Axial Capacity in Cohesive Intermediate Geomaterials and Jointed Rock 345

11.6.5 Design for Axial Capacity in Cohesionless Intermediate Geomaterials 362

11.6.6 Design for Axial Capacity in Massive Rock 365

11.6.7 Addition of Side Resistance and End Bearing in Rock 374

11.6.8 Commentary on Design for Axial Capacity in Karst 375

11.6.9 Comparison of Results from Theory and Experiment 376

Problems 377

12 Fundamental Concepts Regarding Deep Foundations Under Lateral Loading 379

12.1 Introduction 379

12.1.1 Description of the Problem 379

12.1.2 Occurrence of Piles Under Lateral Loading 379

12.1.3 Historical Comment 381

12.2 Derivation of the Differential Equation 382

12.2.1 Solution of the Reduced Form of the Differential Equation 386

12.3 Response of Soil to Lateral Loading 393

12.4 Effect of the Nature of Loading on the Response of Soil 396

12.5 Method of Analysis for Introductory Solutions for a Single Pile 397

12.6 Example Solution Using Nondimensional Charts for Analysis of a Single Pile 401

Problems 411

13 Analysis of Individual Deep Foundations Under Axial Loading Using t-z Model 413

13.1 Short-Term Settlement and Uplift 413

13.1.1 Settlement and Uplift Movements 413

13.1.2 Basic Equations 414

13.1.3 Finite Difference Equations 417

13.1.4 Load-Transfer Curves 417

13.1.5 Load-Transfer Curves for Side Resistance in Cohesive Soil 418

13.1.6 Load-Transfer Curves for End Bearing in Cohesive Soil 419

13.1.7 Load-Transfer Curves for Side Resistance in Cohesionless Soil 421

13.1.8 Load-Transfer Curves for End Bearing in Cohesionless Soil 425

13.1.9 Load-Transfer Curves for Cohesionless Intermediated Geomaterials 426

13.1.10 Example Problem 430

13.1.11 Experimental Techniques for Obtaining Load-Transfer Versus Movement Curves 436

13.2 Design for Vertical Ground Movements Due to Downdrag or Expansive Uplift 437

13.2.1 Downward Movement Due to Downdrag 438

13.2.2 Upward Movement Due to Expansive Uplift 439

Problems 440

14 Analysis and Design By Computer or Piles Subjected to Lateral Loading 441

14.1 Nature of the Comprehensive Problem 441

14.2 Differential Equation for a Comprehensive Solution 442

14.3 Recommendations for p-y Curves for Soil and Rock 443

14.3.1 Introduction 443

14.3.2 Recommendations for p-y Curves for Clays 447

14.3.3 Recommendations for p-y Curves for Sands 464

14.3.4 Modifications to p-y Curves for Sloping Ground 473

14.3.5 Modifications for Raked (Battered Piles) 477

14.3.6 Recommendations for p-y Curves for Rock 478

14.4 Solution of the Differential Equation by Computer 484

14.4.1 Introduction 484

14.4.2 Formulation of the Equation by Finite Differences 486

14.4.3 Equations for Boundary Conditions for Useful Solutions 487

14.5 Implementation of Computer Code 489

14.5.1 Selection of the Length of the Increment 490

14.5.2 Safe Penetration of Pile with No Axial Load 491

14.5.3 Buckling of a Pipe Extending Above the Groundline 492

14.5.4 Steel Pile Supporting a Retaining Wall 492

14.5.5 Drilled Shaft Supporting an Overhead Structure 496

Problems 499

15 Analysis of Pile Groups 503

15.1 Introduction 503

15.2 Distribution of Load to Piles in a Group: The Two-Dimensional Problem 503

15.2.1 Model of the Problem 504

15.2.2 Detailed Step-by-Step Solution Procedure 510

15.3 Modification of p-y Curves for Battered Piles 510

15.4 Example Solution Showing Distribution of a Load to Piles in a Two-Dimensional Group 511

15.4.1 Solution by Hand Computations 511

15.5 Efficiency of Piles in Groups Under Lateral Loading 517

15.5.1 Modifying Lateral Resistance of Closely Spaced Piles 517

15.5.2 Customary Methods of Adjusting Lateral Resistance for Close Spacing 518

15.5.3 Adjusting for Close Spacing under Lateral Loading by Modified p-y Curves 521

15.6 Efficiency of Piles in Groups Under Axial Loading 527

15.6.1 Introduction 527

15.6.2 Efficiency of Piles in a Group in Cohesionless Soils 529

15.6.3 Efficiency of Piles in a Group in Cohesive Soils 531

15.6.4 Concluding Comments 534

Problems 535

Appendix 537

References 539

Index 559