Geotechnical Engineering Principles and Practices of Mechanics and Engineering

V. N. S. Murthy Consulting Geotechnical Engineer Bangalore, India

MARCEL DEKKER, INC. NEW YORK • BASEL CONTENTS

Foreword Mark T. Bowers v Foreword Bengt B. Broms vii Preface ix

CHAPTER 1 INTRODUCTION 1 1.1 General Remarks 1 1.2 A Brief Historical Development 2 1.3 and Foundation Engineering 3

CHAPTER 2 SOIL FORMATION AND CHARACTERIZATION 5 2.1 Introduction 5 2.2 Rock Classification 5 2.3 Formation of 7 2.4 General Types of Soils 7 2.5 Soil Particle Size and Shape 9 2.6 Composition of Minerals 11 2.7 Structure of Clay Minerals 11 2.8 Clay Particle-Water Relations 14 2.9 Soil Mass Structure 17

XI x» Contents

CHAPTER 3 SOIL PHASE RELATIONSHIPS, INDEX PROPERTIES AND CLASSIFICATION 19 3.1 Soil Phase Relationships 19 3.2 Mass-Volume Relationships 20 3.3 Weight-Volume Relationships 24 3.4 Comments on Soil Phase Relationships 25 3.5 Index Properties of Soils 31 3.6 The Shape and Size of Particles 32 3.7 33 3.8 The Method of Analysis 35 3.9 Grain Size Distribution Curves 43 3.10 Relative Density of Cohesionless Soils 44 3.11 Consistency of Clay Soil 45 3.12 Determination of 47 3.13 Discussion on Limits and Indices 52 3.14 Plasticity Chart 59 3.15 General Considerations for Classification of Soils 67 3.16 Field Identification of Soils 68 3.17 Classification of Soils 69 3.18 Textural 69 3.19 AASHTO Soil Classification System 70 3.20 Unified Soil Classification System (USCS) 73 3.21 Comments on the Systems of Soil Classification 76 3.22 Problems' 80

CHAPTER 4 SOIL PERMEABILITY AND SEEPAGE 87 4.1 Soil Permeability 87 4.2 Darcy's Law 89 4.3 Discharge and Seepage Velocities 90 4.4 Methods of Determination of of Soils 91 4.5 Constant Head Permeability Test 92 4.6 Falling Head Permeability Test 93 4.7 Direct Determination of k of Soils in Place by Pumping Test 97 4.8 Permeability Tests 101 4.9 Approximate Values of the Hydraulic Conductivity of Soils 102 4.1Q Hydraulic Conductivity in Stratified Layers of Soils 102 4.11 Empirical Correlations for Hydraulic Conductivity 103 4.12 Hydraulic Conductivity of Rocks by Packer Method 112 4.13 Seepage 114 4.14 Laplace Equation 114 Contents xiii

4.15 Flow Net 116 4.16 Determination of Quantity of Seepage 120 4.17 Determination of Seepage Pressure 122 4.18 Determination of Uplift Pressures 123 4.19 Seepage Flow Through Homogeneous Earth 126 4.20 Flow Net Consisting of Conjugate Confocal Parabolas 127 4.21 Piping Failure 131 4.22 Problems 138

CHAPTER 5 AND 143 5.1 Introduction 143 5.2 Stresses when No Flow Takes Place Through the Saturated Soil Mass 145 5.3 Stresses When Flow Takes Place Through the Soil from Top to Bottom 146 5.4 Stresses When Flow Takes Place Through the Soil from Bottom to Top 147 5.5 Effective Pressure Due to Capillary Water Rise in Soil 149 5.6 Problems 170

CHAPTER 6 STRESS DISTRIBUTION IN SOILS DUE TO SURFACE LOADS 173 '6.1 Introduction 173 6.2 Boussinesq's Formula for Point Loads 174 6.3 Westergaard's Formula for Point Loads 175 6.4 Line Loads 178 6.5 Strip Loads 179 6.6 Stresses Beneath the Corner of a Rectangular Foundation 181 6.7 Stresses Under Uniformly Loaded Circular Footing 186 6.8 Vertical Stress Beneath Loaded Areas of Irregular Shape 188 6.9 Loadings 191

6.10 Approximate Methods for Computing az 197 6.11 Pressure Isobars 198 6.12 Problems . 203

CHAPTER 7 COMPRESSIBILITY AND CONSOLIDATION 207 7.1 Introduction 207 7.2 Consolidation 208 7.3 Consolidometer 212 xiv Contents

7.4 The Standard One-Dimensional Consolidation Test 213 7.5 Pressure- Curves 214 7.6 Determination of Preconsolidation Pressure 218 7.7 e-logp Field Curves for Normally Consolidated and Overconsolidated Clays of Low to Medium Sensitivity 219 7.8 Computation of Consolidation Settlement 219 7.9 Settlement Due to Secondary Compression 224 7.10 Rate of One-dimensional Consolidation Theory of Terzaghi 233 7.11 Determination of the Coefficient of Consolidation 240 7.12 Rate of Settlement Due to Consolidation 242 7.13 Two- and Three-dimensional Consolidation Problems 243 7.14 Problems 247 CHAPTER 8 OF SOIL 253 8.1 Introduction 253 8.2 Basic Concept of Shearing Resistance and Shearing Strength 253 8.3 The Coulomb Equation 254 8.4 Methods of Determining Shear Strength Parameters 255 8.5 Shear Test Apparatus 256 8.6 Stress Condition at a Point in a Soil Mass 260 8.7 Stress Conditions in Soil During Triaxial Compression Test 262 8.8 Relationship Between the Principal Stresses and c 263 8.9 Mohr Circle of Stress 264 8.10 Mohr Circle of Stress When a Prismatic Element is Subjected to Normal and Shear Stresses 265 8.11 Mohr Circle of Stress for a Cylindrical Specimen Compression Test 266 8.12 Mohr-Coulomb Failure Theory 268 8.13 Mohr Diagram for Triaxial Compression Test at Failure 269 8.14 Mohr Diagram for a at Failure 270 8.15 Effective Stresses 274 8.16 Shear Strength Equation in Terms of Effective Principal Stresses 275 8.17 Stress-Controlled and Strain-Controlled Tests 276 8.18 Types of Laboratory Tests 276 8.19 Shearing Strength Tests on . . 278 8.20 Unconsolidated-Undrained Test 284 8.21 Unconfined Compression Tests 286 8.22 Consolidated-Undrained Test on Saturated Clay 294 8.23 Consolidated-Drained Shear Strength Test 296 8.24 Pore Pressure Parameters Under Undrained Loading 298 8.25 Vane Shear Tests 300 Contents xv

8.26 Other Methods for Determining Undrained Shear Strength of Cohesive Soils 302 8.27 The Relationship Between Undrained Shear Strength and Effective 304 8.28 General Comments 310 8.29 Questions and Problems 311

CHAPTER 9 SOIL EXPLORATION 317 9.1 Introduction 317 9.2 Boring of Holes 318 9.3 Sampling in Soil 322 9.4 Rock Core Sampling 325 9.5 Standard Penetration Test 327 9.6 SPT Values Related to Relative Density of Cohesionless Soils 330 9.7 SPT Values Related to Consistency of Clay Soil 330 9.8 Static (CPT) 332 9.9 Pressuremeter 343 9.10 The Flat Dilatometer Test .349 9.11 Field Vane Shear Test (VST) 3 51 9.12 Field Plate Load Test (PLT) 3 51 9.13 Geophysical Exploration 352 9.14 Planning of Soil Exploration 358 9.15 Execution of Soil Exploration Program 359 9.16 Report ' 361 9.17 Problems 362

CHAPTER 10 STABILITY OF SLOPES 365 10.1 Introduction 365 10.2 General Considerations and Assumptions in the Analysis 367 10.3 Factor of Safety 368 10.4 Stability Analysis of Infinite Slopes in Sand 371 10.5 Stability Analysis of Infinite Slopes in Clay 372 10.6 Methods of Stability Analysis of Slopes of Finite Height 376 10.7 Plane Surface of Failure . 376 10.8 Circular Surfaces of Failure 378

10.9 Failure Under Undrained Conditions (u = 0) 380 10.10 -Circle Method 382 10.11 Taylor's Stability Number 389 10.12 Tension Cracks 393 10.13 Stability Analysis by Method of Slices for Steady Seepage 393 xvi Contents

10.14 Bishop's Simplified Method of Slices 400 10.15 Bishop and Morgenstern Method for Slope Analysis 403 10.16 Morgenstern Method of Analysis for Rapid Drawdown Condition 405 10.17 Spencer Method of Analysis 408 10.18 Problems 411

CHAPTER 11 419 11.1 Introduction 419 11.2 Lateral Earth Pressure Theory 420 11.3 Lateral Earth Pressure for at Rest Condition 421 11.4 Rankine's States of Plastic Equilibrium for Cohesionless Soils 425 11.5 Rankine's Earth Pressure Against Smooth Vertical Wall with Cohesionless Backfill 428 11.6 Rankine's Active Earth Pressure with Cohesive Backfill 440 11.7 Rankine's Passive Earth Pressure with Cohesive Backfill 449 11.8 Coulomb's Earth Pressure Theory for Sand for Active State 452 11.9 Coulomb's Earth Pressure Theory for Sand for Passive State 455 11.10 Active Pressure by Culmann's Method for Cohesionless Soils 456 11.11 Lateral Pressures by Theory of Elasticity for Surcharge Loads on the Surface of Backfill 458 11.12 Curved Surfaces of Failure for Computing Passive Earth Pressure 462 11.13 Coefficients of Passive Earth Pressure Tables and Graphs 464 11.14 Lateral Earth Pressure on Retaining Walls During 467 11.15 Problems 476

CHAPTER 12 I: ULTIMATE 481 12.1 Introduction 481 12.2 The Ultimate Bearing Capacity of Soil 483 12.3 Some of the Terms Defined 483 12.4 Types of Failure in Soil 485 12.5 An Overview of Bearing Capacity Theories 487 12.6 Terzaghi's Bearing Capacity Theory 488 12.7 Skempton's Bearing Capacity Factor TV. 493 12.8 Effect of Water Table on Bearing Capacity 494 12.9 The General Bearing Capacity Equation 503 12.10 Effect of Soil Compressibility on Bearing Capacity of Soil 509 12.11 Bearing Capacity of Foundations Subjected to Eccentric Loads 515 12.12 Ultimate Bearing Capacity of Footings Based on SPT Values (AO 518 12.13 The CPT Method of Determining Ultimate Bearing Capacity 518 Contents xvii

12.14 Ultimate Bearing Capacity of Footings Resting on Stratified Deposits of Soil 521 12.15 Bearing Capacity of Foundations on Top of a Slope 529 12.16 Foundations on Rock 532 12.17 Case History of Failure of the Transcona Grain Elevator 533 12.18 Problems 536

CHAPTER 13 SHALLOW FOUNDATION II: SAFE BEARING PRESSURE AND SETTLEMENT CALCULATION 545 13.1 Introduction 545 13.2 Field Plate Load Tests 548 13.3 Effect of Size of Footings on Settlement 554 13.4 Design Charts from SPT Values for Footings on Sand 555 13.5 Empirical Equations Based on SPT Values for Footings on Cohesionless Soils 558 13.6 Safe Bearing Pressure from Empirical Equations Based on CPT Values for Footings on Cohesionless Soil 559 13.7 Foundation Settlement 561 13.8 Evaluation of Modulus of Elasticity 562 13.9 Methods of Computing Settlements 564 13.10 Elastic Settlement Beneath the Corner of a Uniformly Loaded Flexible Area Based on the Theory of Elasticity 565 13.11 Janbu, Bjerrum and Kjaernsli's Method of Determining Elastic Settlement Under Undrained Conditions 568 13.12 Schmertmann's Method of Calculating Settlement in Granular Soils by Using CPT Values 569 13.13 Estimation of Consolidation Settlement by Using Data 575 13.14 Skempton-Bjerrum Method of Calculating Consolidation Settlement (1957) 576 13.15 Problems 580

CHAPTER 14 SHALLOW FOUNDATION III: COMBINED FOOTINGS AND MAT FOUNDATIONS 585 14.1 Introduction 585 14.2 Safe Bearing Pressures for Mat Foundations on Sand and Clay 587 14.3 Eccentric Loading 588 14.4 The Coefficient of Reaction 588 14.5 Proportioning of Cantilever Footing 591 xviii Contents

14.6 Design of Combined Footings by Rigid Method (Conventional Method) " 592 14.7 Design of Mat Foundation by Rigid Method 593 14.8 Design of Combined Footings by Elastic Line Method 594 14.9 Design of Mat Foundations by Elastic Plate Method 595 14.10 Floating Foundation 595 14.11 Problems 603

CHAPTER 15 DEEP FOUNDATION I: PILE FOUNDATION 605 15.1 Introduction 605 15.2 Classification of Piles 605 15.3 Types of Piles According to the Method of Installation 606 15.4 Uses of Piles 608 15.5 Selection of Pile 609 15.6 Installation of Piles 610

PART A-VERTICAL LOAD BEARING CAPACITY OF A SINGLE VERTICAL PILE 613 15.7 General Considerations 613 15.8 Methods of Determining Ultimate Load Bearing Capacity of a Single Vertical Pile 617 15.9 General Theory for Ultimate Bearing Capacity 618 15.10 Ultimate Bearing Capacity in Cohesionless Soils 620 15.11 Critical Depth 621

15.12 Tomlinson's Solution for Qb in Sand 622

15.13 Meyerhof's Method of Determining Qbfor Piles in Sand 624

15.14 Vesic's Method of Determining Qb 625

15.15 Janbu's Method of Determining Qb 628

15.16 Coyle and Castello's Method of Estimating Qb\n Sand 628 15.17 The Ultimate Skin Resistance of a Single Pile in Cohesionless Soil 629

15.18 Skin Resistance Qf by Coyle and Castello Method (1981) 631 15.19 Static Bearing Capacity of Piles in Clay Soil 631 15.20 Bearing Capacity of Piles in Granular Soils Based on SPT Value 635 15.21 Bearing Capacity of Piles Based on Static Cone Penetration Tests (CPT) 652 15.22 Bearing Capacity of a Single Pile by Load Test 663 15.23 Pile Bearing Capacity from Dynamic Pile Driving Formulas 666 15.24 Bearing Capacity of Piles Founded on a Rocky Bed 670 15.25 Uplift Resistance of Piles 671 Contents xix

PART B-PILE GROUP 674 15.26 Number and Spacing of Piles in a Group 674 15.27 Pile Group Efficiency 676 15.28 Vertical Bearing Capacity of Pile Groups Embedded in and 678 15.29 Settlement of Piles and Pile Groups in Sands and Gravels 681 15.30 Settlement of Pile Groups in Cohesive Soils 689 15.31 Allowable Loads on Groups of Piles 690 15.32 Negative Friction 692 15.33 Uplift Capacity of a Pile Group 694 15.34 Problems 696

CHAPTER 16 DEEP FOUNDATION II: BEHAVIOR OF LATERALLY LOADED VERTICAL AND BATTER PILES 699 16.1 Introduction 699 16.2 Winkler's Hypothesis 700 16.3 The Differential Equation 701 16.4 Non-dimensional Solutions for Vertical Piles Subjected to Lateral Loads 704 16.5 p-y Curves for the Solution of Laterally Loaded Piles 706 16.6 Broms' Solutions for Laterally Loaded Piles 709 16.7 A Direct Method for Solving the Non-linear Behavior of Laterally Loaded Flexible Pile Problems 716 16.8 Case Studies for Laterally Loaded Vertical Piles in Sand 722 16.9 Case Studies for Laterally Loaded Vertical Piles in Clay 725 16.10 Behavior of Laterally Loaded Batter Piles in Sand 731 16.11 Problems 739

CHAPTER 17 DEEP FOUNDATION III: DRILLED PIER FOUNDATIONS 741 17.1 Introduction 741 17.2 Types of Drilled Piers 741 17.3 Advantages and Disadvantages of Drilled Pier Foundations 743 17.4 Methods of Construction 743 17.5 Design Considerations 751 17.6 Load Transfer Mechanism 752 17.7 Vertical Bearing Capacity of Drilled Piers 754 17.8 The General Bearing Capacity Equation for the Base Resistance «. (= O 755 xx Contents

17.9 Bearing Capacity Equations for the Base in Cohesive Soil 756 17.10 Bearing Capacity Equation for the Base in Granular Soil 756 17.11 Bearing Capacity Equations for the Base in Cohesive IGM or Rock 759 17.12 The Ultimate Skin Resistance of Cohesive and Intermediate Materials 760 17.13 Ultimate Skin Resistance in Cohesionless Soil and Gravelly Sands 763 17.14 Ultimate Side and Total Resistance in Rock 764 17.15 Estimation of Settlements of Drilled Piers at Working Loads 765 17.16 Uplift Capacity of Drilled Piers 777 17.17 Lateral Bearing Capacity of Drilled Piers 779 17.18 Case Study of a Drilled Pier Subjected to Lateral Loads 787 17.19 Problems 787

CHAPTER 18 FOUNDATIONS ON COLLAPSIBLE AND EXPANSIVE SOILS 791 18.1 General Considerations 791

PART A-COLLAPSIBLE SOILS 793 18.2 General Observations 793 18.3 Collapse Potential and Settlement 795 18.4 Computation of Collapse Settlement 796 18.5 Foundation Design 799 18.6 Treatment .Methods for Collapsible Soils 800

PART B-EXPANSIVE SOILS 800 18.7 Distribution of Expansive Soils 800 18.8 General Characteristics of Swelling Soils 801 18.9 Clay Mineralogy and Mechanism of Swelling 803 18.10 Definition of Some Parameters 804 18.11 Evaluation of the Swelling Potential of Expansive Soils by Single Index Method 804 18.12 Classification of Swelling Soils by Indirect Measurement 806 18.13 Swelling Pressure by Direct Measurement 812 18.14 Effect of Initial Moisture Content and Initial Dry Density on Swelling Pressure 813 18.15 Estimating the Magnitude of Swelling 814 18.16 Design of Foundations in Swelling Soils 817 18.17 Drilled Pier Foundations 817 18.18 Elimination of Swelling 827 18.19 Problems 828 Contents xxi

CHAPTER 19 AND MECHANICALLY STABILIZED EARTH RETAINING WALLS 833 PART A-CONCRETE RETAINING WALLS 833 19.1 Introduction 833 19.2 Conditions Under Which Rankine and Coulomb Formulas Are Applicable to Retaining Walls Under the Active State 833 19.3 Proportioning of Retaining Walls 835 19.4 Earth Pressure Charts for Retaining Walls 836 19.5 Stability of Retaining Walls 839

PART B-MECHANICALLY STABILIZED EARTH RETAINING WALLS 849 19.6 General Considerations 849 19.7 Backfill and Reinforcing Materials 851 19.8 Construction Details 855 19.9 Design Considerations for a Mechanically Stabilized Earth Wall 857 19.10 Design Method 859 19.11 External Stability 863 19.12 Examples of Measured Lateral Earth Pressures 875 19.13 Problems 877

CHAPTER 20 SHEET PILE WALLS AND BRACED CUTS 881 20.1 Introduction 881 20.2 Sheet Pile Structures 883 20.3 Free Cantilever Sheet Pile Walls 883 20.4 Depth of Embedment of Cantilever Walls in Sandy Soils 885 20.5 Depth of Embedment of Cantilever Walls in Cohesive Soils 896 20.6 Anchored Bulkhead: Free-Earth Support Method—Depth of Embedment of Anchored Sheet Piles in Granular Soils 908 20.7 Design Charts for Anchored Bulkheads in Sand 913 20.8 Moment Reduction for Anchored Sheet Pile Walls 916 20.9 Anchorage of Bulkheads 925 20.10 Braced Cuts 931 20.11 Lateral Earth Pressure Distribution on Braced-Cuts 935 20.12 Stability of Braced Cuts in Saturated Clay 938 20.13 Bjerrum and Eide Method of Analysis 940 20.14 Piping Failures in Sand Cuts 945 20.15 Problems 945 XXII Contents

CHAPTER 21 SOIL IMPROVEMENT 951 21.1 Introduction 951 21.2 Mechanical Compaction 952 21.3 Laboratory Tests on Compaction 953 21.4 Effect of Compaction on Engineering Behavior 959 21.5 Field Compaction and Control 962 21.6 Compaction for Deeper Layers of Soil 973 21.7 Preloading 974 21.8 Sand Compaction Piles and Stone Columns 980 21.9 Soil Stabilization by the Use of Admixtures 981 21.10 Soil Stabilization by Injection of Suitable 983 21.11 Problems 983

APPENDIX A SI UNITS IN 987

APPENDIX B SLOPE STABILITY CHARTS AND TABLES 993

REFERENCES 1007

INDEX 1025