Principles of Foundation Engineering Solution Manual by Braja M Das 6th Ed 2007 0495082465

Principles of Foundation Engineering

Principles of Foundation Engineering Sixth Edition

Braja M. Das

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United Kingdom

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United States

Geotechnical Properties of Soil

1

1.1 Introduction 1 1.2 Grain-Size Distribution 2 1.3 Size Limits for Soils 5 1.4 Weight-Volume Relationships 5 1.5 Relative Density 9 1.6 Atterberg Limits 12 1.7 Soil Classification Systems 13 1.8 Hydraulic Conductivity of Soil 21 1.9 Steady-State Seepage 23 1.10 Effective Stress 25 1.11 Consolidation 27 1.12 Calculation of Primary Consolidation Settlement 32 1.13 Time Rate of Consolidation 33 1.14 Degree of Consolidation Under Ramp Loading 40 1.15 Shear Strength 43 1.16 Unconfined Compression Test 48 1.17 Comments on Friction Angle, q;' 49 1.18 Correlations for Undrained Shear Strength, c,, 52 1.19 Sensitivity 53 Problems 54 References 58

2

Natural Soil Deposits and Subsoil Exploration 2.1

Introduction 60

Natural Soil Deposits

2.2

60

60

Soil Origin 60

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Contents

2.3 2.4 2.5 2.6 2.7 2.8 2.9

Residual Soil 61 Gravity Transported Soil 62 Alluvial Deposits 62 Lacustrine Deposits 65 Glacial Deposits 65 Aeolian Soil Deposits 67 Organic Soil 68

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Subsurface Exploration 68 2.10 Purpose of Subsurface Exploration 68 2.11 Subsurface Exploration Program 68 2.12 Exploratory Borings in the Field 71 2.13 Procedures for. Sampling Soil 74 2.14 Observation of Water Tables 85 2.15 Vane Shear Test 86 2.16 Cone Penetration Test 90 2.17 Pressuremeter Test (PMT) 97 2.18 Dilatometer Test 99 2.19 Coring of Rocks 101 2.20 Preparation of Boring Logs 105 2.21 Geophysical Exploration 105 2.22 Subsoil Exploration Report 113 Problems 114 References 119

Shallow Foundations: Ultimate Bearing Capacity 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12

121

Introduction 121 General Concept 121 Terzaghi's Bearing Capacity Theory 124 Factor of Safety 128 Modification of Bearing Capacity Equations for Water Table 130 The General Bearing Capacity Equation 131 Meyerhofs Bearing Capacity, Shape, Depth, and Inclination Factors 136 Some Comments on Bearing Capacity Factor, N,. and Shape Factors 138 A Case History for Bearing Capacity Failure 140 Effect of Soil Compressibility 142 Eccentrically Loaded Foundations 146 Ultimate Bearing Capacity under Eccentric Loading-Meyerhofs Theory 148 3.13 Eccentrically Loaded Foundation-Prakash and Saran's Theory 154 3.14 Bearing Capacity of a Continuous Foundation Subjected to Eccentric Inclined Loading 161 Problems 165 References 168

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Contents

ix

Ultimate Bearing Capacity of Shallow Foundations: Special Cases 170 4.1 4.2 4.3

Introduction 170 Foundation Supported by a Soil with a Rigid Base at Shallow Depth Bearing Capacity of Layered Soils: Stronger Soil Underlain by Weaker Soil 177 4.4 Closely Spaced Foundations-Effect on Ultimate Bearing Capacity 185 4.5 Bearing Capacity of Foundations on Top of a Slope 188 4.6 Bearing Capacity of Foundations on a Slope 191 4.7 Uplift Capacity of Foundations 193 Problems 199 References 202

Shallow Foundations: Allowable Bearing Capacity and Settlement 203 5.1

Introduction 203

Ve~iical si~e;s increase in a Soil Mass Caused by Foundation Load .. 264 5.2 Stress Due to a Concentrated Load 204 5.3 Stress Due to a Circularly Loaded Area 205 5.4 Stress below a Rectangular Area 206 5.5 Average Vertical Stress Increase Due to a Rectangularly Loaded Area 213 5.6 Stress Increase under an Embankment 216 Elastic Settlement 220

5.7 5.8 5.9 5.10 5.11

5.U 5.13 5.14

Elastic Settlement Based on the Theory of Elasticity 220 Elastic Settlement of Foundations on Saturated Clay 230 Improved Equation for Elastic Settlement 230 Settlement of Sandy Soil: Use of Strain Influence Factor 236 Range of Material Parameters for Computing Elastic Settlement 240 Settlement of Foundation on Sand Based on Standard Penetration Resistance 241 General Comments on Elastic Settlement Prediction 246 Seismic Bearing Capacity and Settlement in Granular Soil 247

Cons~lidation Settlement 252 5.15 Primary Consolidation Settlement Relationships 252 5.16 Three-Dimensional Effect on Primary Consolidation Settlement 254 5.17 Settlement Due to Secondary Consolidation 258 5.18 Field Load Test 260

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Contents

5.19 Presumptive Bearing Capacity 263 5.20 Tolerable Settlement of Buildings 264 Problems 266 References 269

6

Mat Foundations

272 ·

6.1 Introduction 272 6.2 Combined Footings 272 6.3 Common Types of Mat Foundations 275 6.4 Bearing Capacity of Mat Foundations 277 6.5 Differential Settlement of Mats 280 6.6 Field Settlement Observations for Mat Foundations 281 6.7 Compensated Foundation 281 6.8 Structural Design of Mat Foundations 285 Problems 304 References 307

7

Lateral Earth Pressure 7.1 7.2

308

Introduction 308 Lateral Earth Pressure at Rest 309

Active Pressure 312 7.3 Rankine Active Earth Pressure 312 7.4 A Generalized Case for Rankine Active Pressure 315 7.5 Coulomb's Active Earth Pressure 323 7.6 Active Earth Pressure for Earthquake Conditions 328 7.7 Active Pressure for Wall Rotation about the Top: Braced Cut 333 7.8 Active Earth Pressure for Translation of Retaining Wall-Granular Backfill 334 7.9 General Comments on Active Earth Pressure 338 Passive Pressure 338 7.10 Rankine Passive Earth Pressure 338 7.11 Rankine Passive Earth Pressure: Inclined Backfill 344 7.12 Coulomb's Passive Earth Pressure 345 7.13 Comments on the Failure Surface Assumption for Coulomb's Pressure Calculations 347 7.14 Passive Pressure under Earthquake Conditions 348 Problems 349 References 352

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Contents

Retaining Walls ~--·

353

Introduction 353

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355 Proportioning Retaining Walls 355 Application of Lateral Earth Pressure Theories to Design 356 Stability of Retaining Walls 358 Check for Overturning 359 Check for Sliding along the Base 361 Check for Bearing Capacity Failure 364 Construction Joints and Drainage from Backfill 374 Some Comments on Design of Retaining Walls 377

Gravity and Cantilever Walls 8.2 8.3 8.4 8.5 8.6 8.7 8.8 8.9

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Soil Reinforcement 379 Considerations in Soil Reinforcement 380 General Design Considerations 382 Retaining Walls with Metallic Strip Reinforcement 383 Step-by-Step-Design Procedure Using Metallic Strip Reinforcement 390 Retaining Walls with Geotextile Reinforcement 395 Retaining Walls with Geogrid Reinforcement 399 General Comments 402 Problems 404 References 407

8.10 8.11 8.12 8.13 8.14 8.15 8.16 8.17

Sheet Pile Walls 9.1 9.2 9.3 9.4 9.5 9.6 9.7 9.8 9.9 9.10 9.11 9.12 9.13 9.14 9.15 9.16

409

Introduction 409 Construction Methods 413 Cantilever Sheet Pile Walls 414 Cantilever Sheet Piling Penetrating Sandy Soils 415 Special Cases for Cantilever Walls Penetrating a Sandy Soil 422 Cantilever Sheet Piling Penetrating Clay 423 Special Cases for Cantilever Walls Penetrating Clay 428 Anchored Sheet-Pile Walls 429 Free Earth Support Method for Penetration of Sandy Soil 430 Design Charts for Free Earth Support Method (Penetration into Sandy Soil) 435 Moment Reduction for Anchored Sheet-Pile Walls 440 Computational Pressure Diagram Method for Penetration into Sandy Soil 443 Field Observations of an Anchored Sheet Pile Wall 447 Free Earth Support Method for Penetration of Clay 448 Anchors 452 Holding Capacity of Anchor Plates in Sand 454

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Contents

9.17 Holding Capacity of Anchor Plates in Clay (cp = 0 Condition) 9.18 Ultimate Resistance of Tiebacks 460 Problems 461 References 464

10

Braced Cuts

460

466

10.1 Introduction 466 10.2 Pressure Envelope for Braced-Cut Design 467 10.3 Pressure Envelope for Cuts in Layered Soil 471 10.4 Design of Various Components of a Braced Cut 472 10.5 Bottom Heave of a Cut in Clay 482 10.6 Stability of the Bottom of a Cut in Sand 485 10.7 Lateral Yielding of Sheet Piles and Ground Settlement 487 Problems 489 References 490

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Pile Foundations 11.1 11.2 11.3 11.4 11.5 11.6 11.7 11.8 11.9 11.10 11.11 11.U 11.13 11.14 11.15 11.16 11.17 11.18 11.19 11.20 11.21

491

Introduction 491 Types of Piles and Their Structural Characteristics 493 Estimating Pile Length 502 Installation of Piles 504 Load Transfer Mechanism 508 Equations for Estimating Pile Capacity 509 Meyerhofs Method for Estimating Q, 512 Vesic's Method for Estimating Q, 515 Janbu's Method for Estimating Q, 516 Coyle and Castello's Method for Estimating Q, in Sand 520 Other Correlations for Calculating Q, with SPT and CPT Results 521 Frictional Resistance (Q,) in Sand 524 Frictional (Skin) Resistance in Clay 528 Point-Bearing Capacity of Piles Resting on Rock 531 Pile Load Tests 538 Comparison of Theory with Field Load Test Results 542 Elastic Settlement of Piles 543 Laterally Loaded Piles 546 Pile-Driving Formulas 562 Pile Capacity For Vibration-Driven Piles 568 Negative Skin Friction 570

Group Pile; 573 11.22 Group Efficiency 573 11.23 Ultimate Capacity of Group Piles in Saturated Clay 576 11.24 Elastic Settlement of Group Piles 580

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Contents

11.25 Consolidation Settlement of Group Piles 11.26 Piles in Rock 584 Problems 584 References 588

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Drilled-Shaft Foundations

581

591

U.1 U.2 U.3 U.4

Introduction 591 Types of Drilled Shafts 592 Construction Procedures 593 Other Design Considerations 598 u.s Load Transfer Mechanism 598 U.6 Estimation of Load-Bearing Capacity 599 U.7 Drilled Shafts in Granular Soil: Load-Bearing Capacity 602 U.8 Drilled Shafts in Clay: Load-Bearing Capacity 613 U.9 Settlement of Drilled Shafts at Working Load 620 U.10 Lateral Load-Carrying Capacity-Characteristic Load and Moment Method 622 U.11 Drilled Shafts Extending into Rock 631 Problems 635 References 639

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Foundations on Difficult Soils

640

13.1 Introduction 640 640 Definition and Types of Collapsible Soil 640 Physical Parameters for Identification 641 Procedure for Calculating Collapse Settlement 645 Foundation Design in Soils Not Susceptible to Wetting 646 Foundation Design in Soils Susceptible to Wetting 648

Collapsible Soil

13.2 13.3 13.4 13.S 13.6

649 13.7 General Nature of Expansive Soils 649 13.8 Laboratory Measurement of Swell 650 13.9· Classification of Expansive Soil on the Basis of Index Tests 655 13.10 Foundation Considerations for Expansive Soils 656 13.11 Construction on Expansive Soils' 661 Expansive Soils

Sanitary Landfills 665 13.U General Nature of Sanitary Landfills 665 13.13 Settlement of Sanitary Landfills 666 Problems 668 References 670 I

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xiv

Contents

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Soil Improvement and Ground Modification

672

Introduction 672 General Principles of Compaction 673 Correction for Compaction of Soils with Oversized Particles 676 Field Compaction 678 Compaction Control for Clay Hydraulic Barriers 681 Vibroflotation 682 Precompression 688 Sand Drains 696 Prefabricated Vertical Drains 706 Lime Stabilization 711 Cement Stabilization 714 Fly-Ash Stabilization 716 Stone Columns 717 Sand Compaction Piles 722 Dynamic Compaction 725 Jet Grouting 727 Problems 729 References 731

14.1 14.2 14.3 14.4 14.5 14.6 14.7 14.8 14.9 14.10 14.11 14.12 14.13 14.14 14.15 14.16

Appendix A 735 Answers to Selected Problems 740 Index 745

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