Principles of Foundation Engineering 7th Edition SI Units ED PDF

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CONVERSION FACTORS FROM ENGLISH TO SI UNITS Length: 1 ft 5 0.3048 m Stress: 1 lb>ft 2 5 47.88 N>m2 1 ft 5 30.48 cm 1 lb>ft 2 5 0.04788 kN>m2 1 ft 5 304.8 mm 1 U.S. ton>ft 2 5 95.76 kN>m2 1 in. 5 0.0254 m 1 kip>ft 2 5 47.88 kN>m2 1 in. 5 2.54 cm 1 lb>in2 5 6.895 kN>m2 1...

Description

CONVERSION FACTORS FROM ENGLISH TO SI UNITS Length:

Area:

Volume:

Force:

1 ft 1 ft 1 ft 1 in. 1 in. 1 in. 2

5 5 5 5 5 5

0.3048 m 30.48 cm 304.8 mm 0.0254 m 2.54 cm 25.4 mm 24

Stress:

1 lb>ft 2 1 lb>ft 2 1 U.S. ton>ft 2 1 kip>ft 2 1 lb>in2

5 5 5 5 5

Unit weight:

1 lb>ft 3 1 lb>in3

5 0.1572 kN>m3 5 271.43 kN>m3

Moment:

1 lb-ft 1 lb-in.

5 1.3558 N # m 5 0.11298 N # m

Energy:

1 ft-lb

5 1.3558 J

Moment of inertia:

1 in4 1 in4

5 0.4162 3 106 mm4 5 0.4162 3 1026 m4

Section modulus:

1 in3 1 in3

5 0.16387 3 105 mm3 5 0.16387 3 1024 m3

Hydraulic conductivity:

1 ft>min 1 ft>min 1 ft>min 1 ft>sec 1 ft>sec 1 in.>min 1 in.>sec 1 in.>sec

5 0.3048 m>min 5 30.48 cm>min 5 304.8 mm>min 5 0.3048 m>sec 5 304.8 mm>sec 5 0.0254 m>min 5 2.54 cm>sec 5 25.4 mm>sec

2

1 ft 1 ft 2 1 ft 2 1 in2 1 in2 1 in2

5 5 5 5 5 5

929.03 3 10 m 929.03 cm2 929.03 3 102 mm2 6.452 3 1024 m2 6.452 cm2 645.16 mm2

1 ft 3 1 ft 3 1 in3 1 in3

5 28.317 3 1023 m3 5 28.317 3 103 cm3 5 16.387 3 1026 m3 5 16.387 cm3

1 lb 1 lb 1 lb 1 kip 1 U.S. ton 1 lb 1 lb>ft

5 4.448 N 5 4.448 3 1023 kN 5 0.4536 kgf 5 4.448 kN 5 8.896 kN 5 0.4536 3 1023 metric ton 5 14.593 N>m

Coefficient of consolidation:

1 in2>sec 1 in2>sec 1 ft 2>sec

47.88 N>m2 0.04788 kN>m2 95.76 kN>m2 47.88 kN>m2 6.895 kN>m2

5 6.452 cm2>sec 5 20.346 3 103 m2>yr 5 929.03 cm2>sec

Principles of Foundation Engineering, SI Seventh Edition

BRAJA M. DAS

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Principles of Foundation Engineering, SI Seventh Edition Author Braja M. Das Publisher, Global Engineering: Christopher M. Shortt Senior Developmental Editor: Hilda Gowans Editorial Assistant: Tanya Altieri Team Assistant: Carly Rizzo Marketing Manager: Lauren Betsos Production Manager: Patricia M. Boies Content Project Manager: Darrell Frye Production Service: RPK Editorial Services, Inc. Copyeditor: Shelly Gerger-Knecthl Proofreader: Martha McMaster Indexer: Braja M. Das

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Printed in the United States of America 1 2 3 4 5 6 7 13 12 11 10 09

To our granddaughter, Elizabeth Madison

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Contents

Preface xvii

1

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 10 1.6 Atterberg Limits 15 1.7 Liquidity Index 16 1.8 Activity 17 1.9 Soil Classification Systems 17 1.10 Hydraulic Conductivity of Soil 25 1.11 Steady-State Seepage 28 1.12 Effective Stress 30 1.13 Consolidation 32 1.14 Calculation of Primary Consolidation Settlement 37 1.15 Time Rate of Consolidation 38 1.16 Degree of Consolidation Under Ramp Loading 44 1.17 Shear Strength 47 1.18 Unconfined Compression Test 52 1.19 Comments on Friction Angle, fr 54 1.20 Correlations for Undrained Shear Strength, Cu 57 1.21 Sensitivity 57 Problems 58 References 62

vii

viii

Contents

2

Natural Soil Deposits and Subsoil Exploration 64 2.1 Introduction 64 Natural Soil Deposits 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10

64

Soil Origin 64 Residual Soil 66 Gravity Transported Soil 67 Alluvial Deposits 68 Lacustrine Deposits 70 Glacial Deposits 70 Aeolian Soil Deposits 71 Organic Soil 73 Some Local Terms for Soils 73

Subsurface Exploration

74

2.11 Purpose of Subsurface Exploration 74 2.12 Subsurface Exploration Program 74 2.13 Exploratory Borings in the Field 77 2.14 Procedures for Sampling Soil 81 2.15 Split-Spoon Sampling 81 2.16 Sampling with a Scraper Bucket 89 2.17 Sampling with a Thin-Walled Tube 90 2.18 Sampling with a Piston Sampler 92 2.19 Observation of Water Tables 92 2.20 Vane Shear Test 94 2.21 Cone Penetration Test 98 2.22 Pressuremeter Test (PMT) 107 2.23 Dilatometer Test 110 2.24 Coring of Rocks 113 2.25 Preparation of Boring Logs 117 2.26 Geophysical Exploration 118 2.27 Subsoil Exploration Report 126 Problems 126 References 130

3

Shallow Foundations: Ultimate Bearing Capacity 133 3.1 3.2 3.3 3.4

Introduction 133 General Concept 133 Terzaghi’s Bearing Capacity Theory 136 Factor of Safety 140

Contents

3.5 3.6 3.7 3.8 3.9 3.10

Modification of Bearing Capacity Equations for Water Table 142 The General Bearing Capacity Equation 143 Case Studies on Ultimate Bearing Capacity 148 Effect of Soil Compressibility 153 Eccentrically Loaded Foundations 157 Ultimate Bearing Capacity under Eccentric Loading—One-Way Eccentricity 159 3.11 Bearing Capacity—Two-way Eccentricity 165 3.12 Bearing Capacity of a Continuous Foundation Subjected to Eccentric Inclined Loading 173 Problems 177 References 179

4

Ultimate Bearing Capacity of Shallow Foundations: Special Cases 181 4.1 Introduction 181 4.2 Foundation Supported by a Soil with a Rigid Base at Shallow Depth 181 4.3 Bearing Capacity of Layered Soils: Stronger Soil Underlain by Weaker Soil 190 4.4 Bearing Capacity of Layered Soil: Weaker Soil Underlain by Stronger Soil 198 4.5 Closely Spaced Foundations—Effect on Ultimate Bearing Capacity 200 4.6 Bearing Capacity of Foundations on Top of a Slope 203 4.7 Seismic Bearing Capacity of a Foundation at the Edge of a Granular Soil Slope 209 4.8 Bearing Capacity of Foundations on a Slope 210 4.9 Foundations on Rock 212 4.10 Uplift Capacity of Foundations 213 Problems 219 References 221

5

Shallow Foundations: Allowable Bearing Capacity and Settlement 223 5.1 Introduction 223 Vertical Stress Increase in a Soil Mass Caused by Foundation Load 5.2 Stress Due to a Concentrated Load 224

224

ix

x Contents

5.3 Stress Due to a Circularly Loaded Area 224 5.4 Stress below a Rectangular Area 226 5.5 Average Vertical Stress Increase Due to a Rectangularly Loaded Area 232 5.6 Stress Increase under an Embankment 236 5.7 Westergaard’s Solution for Vertical Stress Due to a Point Load 240 5.8 Stress Distribution for Westergaard Material 241 Elastic Settlement 243 Elastic Settlement of Foundations on Saturated Clay (␮S ⫽ 0.5) 243 Settlement Based on the Theory of Elasticity 245 Improved Equation for Elastic Settlement 254 Settlement of Sandy Soil: Use of Strain Influence Factor 258 Settlement of Foundation on Sand Based on Standard Penetration Resistance 263 5.14 Settlement in Granular Soil Based on Pressuremeter Test (PMT) 267 5.9 5.10 5.11 5.12 5.13

Consolidation Settlement

273

5.15 Primary Consolidation Settlement Relationships 273 5.16 Three-Dimensional Effect on Primary Consolidation Settlement 274 5.17 Settlement Due to Secondary Consolidation 278 5.18 Field Load Test 280 5.19 Presumptive Bearing Capacity 282 5.20 Tolerable Settlement of Buildings 283 Problems 285 References 288

6

Mat Foundations 291 6.1 Introduction 291 6.2 Combined Footings 291 6.3 Common Types of Mat Foundations 294 6.4 Bearing Capacity of Mat Foundations 296 6.5 Differential Settlement of Mats 299 6.6 Field Settlement Observations for Mat Foundations 300 6.7 Compensated Foundation 300 6.8 Structural Design of Mat Foundations 304 Problems 322 References 323

Contents

7

Lateral Earth Pressure 324 7.1 Introduction 324 7.2 Lateral Earth Pressure at Rest 325 Active Pressure 7.3 7.4 7.5 7.6 7.7 7.8 7.9

328

Rankine Active Earth Pressure 328 A Generalized Case for Rankine Active Pressure 334 Coulomb’s Active Earth Pressure 340 Active Earth Pressure Due to Surcharge 348 Active Earth Pressure for Earthquake Conditions 350 Active Pressure for Wall Rotation about the Top: Braced Cut 355 Active Earth Pressure for Translation of Retaining Wall—Granular Backfill 357

Passive Pressure

360

7.10 Rankine Passive Earth Pressure 360 7.11 Rankine Passive Earth Pressure: Vertical Backface and Inclined Backfill 363 7.12 Coulomb’s Passive Earth Pressure 365 7.13 Comments on the Failure Surface Assumption for Coulomb’s Pressure Calculations 366 7.14 Passive Pressure under Earthquake Conditions 370 Problems 371 References 373

8

Retaining Walls 375 8.1 Introduction 375 Gravity and Cantilever Walls 8.2 8.3 8.4 8.5 8.6 8.7 8.8 8.9 8.10

377

Proportioning Retaining Walls 377 Application of Lateral Earth Pressure Theories to Design 378 Stability of Retaining Walls 380 Check for Overturning 382 Check for Sliding along the Base 384 Check for Bearing Capacity Failure 387 Construction Joints and Drainage from Backfill 396 Gravity Retaining-Wall Design for Earthquake Conditions 399 Comments on Design of Retaining Walls and a Case Study 402

Mechanically Stabilized Retaining Walls 8.11 Soil Reinforcement 405

405

xi

xii Contents

8.12 8.13 8.14 8.15

Considerations in Soil Reinforcement 406 General Design Considerations 409 Retaining Walls with Metallic Strip Reinforcement 410 Step-by-Step-Design Procedure Using Metallic Strip Reinforcement 417 8.16 Retaining Walls with Geotextile Reinforcement 422 8.17 Retaining Walls with Geogrid Reinforcement—General 428 8.18 Design Procedure fore Geogrid-Reinforced Retaining Wall 428 Problems 433 References 435

9

Sheet Pile Walls 437 9.1 9.2 9.3 9.4 9.5

Introduction 437 Construction Methods 441 Cantilever Sheet Pile Walls 442 Cantilever Sheet Piling Penetrating Sandy Soils 442 Special Cases for Cantilever Walls Penetrating a Sandy Soil 449 9.6 Cantilever Sheet Piling Penetrating Clay 452 9.7 Special Cases for Cantilever Walls Penetrating Clay 457 9.8 Anchored Sheet-Pile Walls 460 9.9 Free Earth Support Method for Penetration of Sandy Soil 461 9.10 Design Charts for Free Earth Support Method (Penetration into Sandy Soil) 465 9.11 Moment Reduction for Anchored Sheet-Pile Walls 469 9.12 Computational Pressure Diagram Method for Penetration into Sandy Soil 472 9.13 Fixed Earth-Support Method for Penetration into Sandy Soil 476 9.14 Field Observations for Anchor Sheet Pile Walls 479 9.15 Free Earth Support Method for Penetration of Clay 482 9.16 Anchors 486 9.17 Holding Capacity of Anchor Plates in Sand 488 9.18 Holding Capacity of Anchor Plates in Clay (f 5 0 Condition) 495 9.19 Ultimate Resistance of Tiebacks 495 Problems 497 References 500

Contents

10

Braced Cuts 501 10.1 Introduction 501 10.2 Pressure Envelope for Braced-Cut Design 502 10.3 Pressure Envelope for Cuts in Layered Soil 506 10.4 Design of Various Components of a Braced Cut 507 10.5 Case Studies of Braced Cuts 515 10.6 Bottom Heave of a Cut in Clay 520 10.7 Stability of the Bottom of a Cut in Sand 524 10.8 Lateral Yielding of Sheet Piles and Ground Settlement 529 Problems 531 References 533

11

Pile Foundations 535 11.1 11.2 11.3 11.4 11.5 11.6 11.7 11.8 11.9 11.10 11.11 11.12 11.13 11.14 11.15 11.16 11.17 11.18 11.19

Introduction 535 Types of Piles and Their Structural Characteristics 537 Estimating Pile Length 546 Installation of Piles 548 Load Transfer Mechanism 551 Equations for Estimating Pile Capacity 554 Meyerhof’s Method for Estimating Qp 557 Vesic’s Method for Estimating Qp 560 Coyle and Castello’s Method for Estimating Qp in Sand 563 Correlations for Calculating Qp with SPT and CPT Results 567 Frictional Resistance (Qs) in Sand 568 Frictional (Skin) Resistance in Clay 575 Point Bearing Capacity of Piles Resting on Rock 579 Pile Load Tests 583 Elastic Settlement of Piles 588 Laterally Loaded Piles 591 Pile-Driving Formulas 606 Pile Capacity For Vibration-Driven Piles 611 Negative Skin Friction 613

Group Piles

617

11.20 Group Efficiency 617 11.21 Ultimate Capacity of Group Piles in Saturated Clay 621 11.22 Elastic Settlement of Group Piles 624 11.23 Consolidation Settlement of Group Piles 626

xiii

xiv

Contents

11.24 Piles in Rock 629 Problems 629 References 634

12

Drilled-Shaft Foundations 637 12.1 12.2 12.3 12.4 12.5 12.6 12.7

Introduction 637 Types of Drilled Shafts 638 Construction Procedures 639 Other Design Considerations 645 Load Transfer Mechanism 646 Estimation of Load-Bearing Capacity 646 Drilled Shafts in Granular Soil: Load-Bearing Capacity 648 12.8 Load-Bearing Capacity Based on Settlement 652 12.9 Drilled Shafts in Clay: Load-Bearing Capacity 661 12.10 Load-Bearing Capacity Based on Settlement 663 12.11 Settlement of Drilled Shafts at Working Load 668 12.12 Lateral Load-Carrying Capacity—Characteristic Load and Moment Method 670 12.13 Drilled Shafts Extending into Rock 679 Problems 681 References 685

13

Foundations on Difficult Soils 686 13.1 Introduction 686 Collapsible Soil

686

13.2 13.3 13.4 13.5

Definition and Types of Collapsible Soil 686 Physical Parameters for Identification 687 Procedure for Calculating Collapse Settlement 691 Foundation Design in Soils Not Susceptible to Wetting 692 13.6 Foundation Design in Soils Susceptible to Wetting 694 Expansive Soils 13.7 13.8 13.9 13.10

695

General Nature of Expansive Soils 695 Unrestrained Swell Test 699 Swelling Pressure Test 700 Classification of Expansive Soil on the Basis of Index Tests 705

Contents

13.11 Foundation Considerations for Expansive Soils 708 13.12 Construction on Expansive Soils 711 Sanitary Landfills

716

13.13 General Nature of Sanitary Landfills 716 13.14 Settlement of Sanitary Landfills 717 Problems 719 References 720

14

Soil Improvement and Ground Modification 722 14.1 Introduction 722 14.2 General Principles of Compaction 723 14.3 Field Compaction 727 14.4 Compaction Control for Clay Hydraulic Barriers 730 14.5 Vibroflotation 732 14.6 Blasting 739 14.7 Precompression 739 14.8 Sand Drains 745 14.9 Prefabricated Vertical Drains 756 14.10 Lime Stabilization 760 14.11 Cement Stabilization 764 14.12 Fly-Ash Stabilization 766 14.13 Stone Columns 767 14.14 Sand Compaction Piles 772 14.15 Dynamic Compaction 774 14.16 Jet Grouting 776 Problems 778 References 781

Answers to Selected Problems 783 Index 789

xv

Preface

Soil mechanics and foundation engineering have developed rapidly during the last fifty years. Intensive research and observation in the field and the laboratory have refined and improved the science of foundation design. Originally published in the fall of 1983 with a 1984 copyright, this text on the principles of foundation engineering is now in the seventh edition. The use of this text throughout the world has increased greatly over the years; it also has been translated into several languages. New and improved materials that have been published in various geotechnical engineering journals and conference proceedings have been incorporated into each edition of the text. Principles of Foundation Engineering is intended primarily for undergraduate civil engineering students. The first chapter, on Geotechnical Properties of Soil, reviews the topics covered in the introductory soil mechanics course, which is a prerequisite for the foundation engineering course. The text is composed of fourteen chapters with examples and problems, and an answer section for selected problems. The chapters are mostly devoted to the geotechnical aspects of foundation design. Both Systéime International (SI) units and English units are used in the text. Because the text introduces the application of fundamental concepts of foundation analysis and design to civil engineering students, the mathematical derivations are not always presented; instead, just the final form of the equation is given. A list of references for further information and study is included at the end of each chapter. Each chapter contains many example problems that will help students understand the application of the equations and graphs. For better understanding and visualization of the ideas and field practices, about thirty new photographs have been added in this edition. A number of practice problems also are given at the end of each chapter. Answers to some of these problems are given at the end of the text. The following is a brief overview of the changes from the sixth edition. • • •

•

In several parts of the text, the presentation has been thoroughly reorganized for better understanding. A number of new case studies have been added to familiarize students with the deviations from theory to practice. In Chapter 1 on Geotechnical Properties of Soil, new sections on liquidity index and activity have been added. The discussions on hydraulic conductivity of clay, relative density, and the friction angle of granular soils have been expanded. Expanded treatment of the weathering process of rocks is given in Chapter 2, Natural Soil Deposits and Subsoil Exploration. xvii

xviii

Preface

•

•

•

•

• • • • •

In Chapter 3 (Shallow Foundations: Ultimate Bearing Capacity), a new case study on bearing capacity failure in soft saturated clay has been added. Also included is the reduction factor method for estimating the ultimate bearing capacity of eccentrically loaded strip foundations on granular soil. Chapter 4, Ultimate Bearing Capacity of...