GeotechnicalEngineering

Principles and Practices of Soil Mechanicsand Foundation Engineering

V. N. S. MurthyConsulting Geotechnical EngineerBangalore, India

MARCEL DEKKER, INC. N E W YORK • BASEL

CONTENTS

Foreword Mark T. Bowers v

Foreword Bengt B. Broms vii

Preface ix

CHAPTER 1 INTRODUCTION 11.1 General Remarks 11.2 A Brief Historical Development 21.3 Soil Mechanics and Foundation Engineering 3

CHAPTER 2 SOIL FORMATION AND CHARACTERIZATION 52.1 Introduction 52.2 Rock Classification 52.3 Formation of Soils 72.4 General Types of Soils 72.5 Soil Particle Size and Shape 92.6 Composition of Clay Minerals 112.7 Structure of Clay Minerals 112.8 Clay Particle-Water Relations 142.9 Soil Mass Structure 17

X I

x» Contents

CHAPTER 3 SOIL PHASE RELATIONSHIPS, INDEX PROPERTIESAND CLASSIFICATION 19

3.1 Soil Phase Relationships 193.2 Mass-Volume Relationships 203.3 Weight-Volume Relationships 243.4 Comments on Soil Phase Relationships 253.5 Index Properties of Soils 313.6 The Shape and Size of Particles 323.7 Sieve Analysis 333.8 The Hydrometer Method of Analysis 353.9 Grain Size Distribution Curves 433.10 Relative Density of Cohesionless Soils 443.11 Consistency of Clay Soil 453.12 Determination of Atterberg Limits 473.13 Discussion on Limits and Indices 523.14 Plasticity Chart 593.15 General Considerations for Classification of Soils 673.16 Field Identification of Soils 683.17 Classification of Soils 693.18 Textural Soil Classification 693.19 AASHTO Soil Classification System 703.20 Unified Soil Classification System (USCS) 733.21 Comments on the Systems of Soil Classification 763.22 Problems' 80

CHAPTER 4 SOIL PERMEABILITY AND SEEPAGE 874.1 Soil Permeability 874.2 Darcy's Law 894.3 Discharge and Seepage Velocities 904.4 Methods of Determination of Hydraulic Conductivity of Soils 914.5 Constant Head Permeability Test 924.6 Falling Head Permeability Test 934.7 Direct Determination of k of Soils in Place by Pumping Test 974.8 Borehole Permeability Tests 1014.9 Approximate Values of the Hydraulic Conductivity of Soils 1024.1Q Hydraulic Conductivity in Stratified Layers of Soils 1024.11 Empirical Correlations for Hydraulic Conductivity 1034.12 Hydraulic Conductivity of Rocks by Packer Method 1124.13 Seepage 1144.14 Laplace Equation 114

Contents xiii

4.15 Flow Net Construction 1164.16 Determination of Quantity of Seepage 1204.17 Determination of Seepage Pressure 1224.18 Determination of Uplift Pressures 1234.19 Seepage Flow Through Homogeneous Earth Dams 1264.20 Flow Net Consisting of Conjugate Confocal Parabolas 1274.21 Piping Failure 1314.22 Problems 138

CHAPTER 5 EFFECTIVE STRESS AND PORE WATER PRESSURE 1435.1 Introduction 1435.2 Stresses when No Flow Takes Place Through the

Saturated Soil Mass 1455.3 Stresses When Flow Takes Place Through the Soil

from Top to Bottom 1465.4 Stresses When Flow Takes Place Through the Soil

from Bottom to Top 1475.5 Effective Pressure Due to Capillary Water Rise in Soil 1495.6 Problems 170

CHAPTER 6 STRESS DISTRIBUTION IN SOILSDUE TO SURFACE LOADS 173'6.1 Introduction 173

6.2 Boussinesq's Formula for Point Loads 1746.3 Westergaard's Formula for Point Loads 1756.4 Line Loads 1786.5 Strip Loads 1796.6 Stresses Beneath the Corner of a Rectangular Foundation 1816.7 Stresses Under Uniformly Loaded Circular Footing 1866.8 Vertical Stress Beneath Loaded Areas of Irregular Shape 1886.9 Embankment Loadings 1916.10 Approximate Methods for Computing az 1976.11 Pressure Isobars 1986.12 Problems . 203

CHAPTER 7 COMPRESSIBILITY AND CONSOLIDATION 2077.1 Introduction 2077.2 Consolidation 2087.3 Consolidometer 212

xiv Contents

7.4 The Standard One-Dimensional Consolidation Test 2137.5 Pressure-Void Ratio Curves 2147.6 Determination of Preconsolidation Pressure 2187.7 e-logp Field Curves for Normally Consolidated and

Overconsolidated Clays of Low to Medium Sensitivity 2197.8 Computation of Consolidation Settlement 2197.9 Settlement Due to Secondary Compression 2247.10 Rate of One-dimensional Consolidation Theory of Terzaghi 2337.11 Determination of the Coefficient of Consolidation 2407.12 Rate of Settlement Due to Consolidation 2427.13 Two- and Three-dimensional Consolidation Problems 2437.14 Problems 247

CHAPTER 8 SHEAR STRENGTH OF SOIL 2538.1 Introduction 2538.2 Basic Concept of Shearing Resistance and Shearing Strength 2538.3 The Coulomb Equation 2548.4 Methods of Determining Shear Strength Parameters 2558.5 Shear Test Apparatus 2568.6 Stress Condition at a Point in a Soil Mass 2608.7 Stress Conditions in Soil During Triaxial Compression Test 2628.8 Relationship Between the Principal Stresses and Cohesion c 2638.9 Mohr Circle of Stress 2648.10 Mohr Circle of Stress When a Prismatic Element is Subjected to

Normal and Shear Stresses 2658.11 Mohr Circle of Stress for a Cylindrical Specimen

Compression Test 2668.12 Mohr-Coulomb Failure Theory 2688.13 Mohr Diagram for Triaxial Compression Test at Failure 2698.14 Mohr Diagram for a Direct Shear Test at Failure 2708.15 Effective Stresses 2748.16 Shear Strength Equation in Terms of Effective Principal Stresses 2758.17 Stress-Controlled and Strain-Controlled Tests 2768.18 Types of Laboratory Tests 2768.19 Shearing Strength Tests on Sand . . 2788.20 Unconsolidated-Undrained Test 2848.21 Unconfined Compression Tests 2868.22 Consolidated-Undrained Test on Saturated Clay 2948.23 Consolidated-Drained Shear Strength Test 2968.24 Pore Pressure Parameters Under Undrained Loading 2988.25 Vane Shear Tests 300

Contents xv

8.26 Other Methods for Determining Undrained Shear Strengthof Cohesive Soils 302

8.27 The Relationship Between Undrained Shear Strength andEffective Overburden Pressure 304

8.28 General Comments 3108.29 Questions and Problems 311

CHAPTER 9 SOIL EXPLORATION 3179.1 Introduction 3179.2 Boring of Holes 3189.3 Sampling in Soil 3229.4 Rock Core Sampling 3259.5 Standard Penetration Test 3279.6 SPT Values Related to Relative Density of Cohesionless Soils 3309.7 SPT Values Related to Consistency of Clay Soil 3309.8 Static Cone Penetration Test (CPT) 3329.9 Pressuremeter 3439.10 The Flat Dilatometer Test .3499.11 Field Vane Shear Test (VST) 3 519.12 Field Plate Load Test (PLT) 3 519.13 Geophysical Exploration 3529.14 Planning of Soil Exploration 3589.15 Execution of Soil Exploration Program 3599.16 Report ' 3619.17 Problems 362

CHAPTER 10 STABILITY OF SLOPES 36510.1 Introduction 36510.2 General Considerations and Assumptions in the Analysis 367

10.3 Factor of Safety 36810.4 Stability Analysis of Infinite Slopes in Sand 37110.5 Stability Analysis of Infinite Slopes in Clay 37210.6 Methods of Stability Analysis of Slopes of Finite Height 37610.7 Plane Surface of Failure . 37610.8 Circular Surfaces of Failure 37810.9 Failure Under Undrained Conditions (</>u = 0) 38010.10 Friction-Circle Method 38210.11 Taylor's Stability Number 38910.12 Tension Cracks 39310.13 Stability Analysis by Method of Slices for Steady Seepage 393

xvi Contents

10.14 Bishop's Simplified Method of Slices 40010.15 Bishop and Morgenstern Method for Slope Analysis 40310.16 Morgenstern Method of Analysis for Rapid Drawdown Condition 40510.17 Spencer Method of Analysis 40810.18 Problems 411

CHAPTER 11 LATERAL EARTH PRESSURE 41911.1 Introduction 41911.2 Lateral Earth Pressure Theory 42011.3 Lateral Earth Pressure for at Rest Condition 42111.4 Rankine's States of Plastic Equilibrium for Cohesionless Soils 42511.5 Rankine's Earth Pressure Against Smooth Vertical Wall with

Cohesionless Backfill 42811.6 Rankine's Active Earth Pressure with Cohesive Backfill 44011.7 Rankine's Passive Earth Pressure with Cohesive Backfill 44911.8 Coulomb's Earth Pressure Theory for Sand for Active State 45211.9 Coulomb's Earth Pressure Theory for Sand for Passive State 45511.10 Active Pressure by Culmann's Method for Cohesionless Soils 45611.11 Lateral Pressures by Theory of Elasticity for Surcharge Loads

on the Surface of Backfill 45811.12 Curved Surfaces of Failure for Computing Passive Earth Pressure 46211.13 Coefficients of Passive Earth Pressure Tables and Graphs 46411.14 Lateral Earth Pressure on Retaining Walls During Earthquakes 46711.15 Problems 476

CHAPTER 12 SHALLOW FOUNDATION I:ULTIMATE BEARING CAPACITY 481

12.1 Introduction 481

12.2 The Ultimate Bearing Capacity of Soil 48312.3 Some of the Terms Defined 48312.4 Types of Failure in Soil 48512.5 An Overview of Bearing Capacity Theories 48712.6 Terzaghi's Bearing Capacity Theory 48812.7 Skempton's Bearing Capacity Factor TV. 49312.8 Effect of Water Table on Bearing Capacity 49412.9 The General Bearing Capacity Equation 50312.10 Effect of Soil Compressibility on Bearing Capacity of Soil 50912.11 Bearing Capacity of Foundations Subjected to Eccentric Loads 51512.12 Ultimate Bearing Capacity of Footings Based on SPT Values (AO 51812.13 The CPT Method of Determining Ultimate Bearing Capacity 518

Contents xvii

12.14 Ultimate Bearing Capacity of Footings Resting on StratifiedDeposits of Soil 521

12.15 Bearing Capacity of Foundations on Top of a Slope 52912.16 Foundations on Rock 53212.17 Case History of Failure of the Transcona Grain Elevator 53312.18 Problems 536

CHAPTER 13 SHALLOW FOUNDATION II:SAFE BEARING PRESSURE AND SETTLEMENT CALCULATION 545

13.1 Introduction 54513.2 Field Plate Load Tests 54813.3 Effect of Size of Footings on Settlement 55413.4 Design Charts from SPT Values for Footings on Sand 55513.5 Empirical Equations Based on SPT Values for Footings on

Cohesionless Soils 55813.6 Safe Bearing Pressure from Empirical Equations Based on

CPT Values for Footings on Cohesionless Soil 55913.7 Foundation Settlement 56113.8 Evaluation of Modulus of Elasticity 56213.9 Methods of Computing Settlements 56413.10 Elastic Settlement Beneath the Corner of a Uniformly Loaded

Flexible Area Based on the Theory of Elasticity 56513.11 Janbu, Bjerrum and Kjaernsli's Method of Determining

Elastic Settlement Under Undrained Conditions 56813.12 Schmertmann's Method of Calculating Settlement in Granular

Soils by Using CPT Values 56913.13 Estimation of Consolidation Settlement by Using Oedometer

Test Data 57513.14 Skempton-Bjerrum Method of Calculating Consolidation

Settlement (1957) 57613.15 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 58714.3 Eccentric Loading 58814.4 The Coefficient of Subgrade Reaction 58814.5 Proportioning of Cantilever Footing 591

xviii Contents

14.6 Design of Combined Footings by Rigid Method (ConventionalMethod) " 592

14.7 Design of Mat Foundation by Rigid Method 59314.8 Design of Combined Footings by Elastic Line Method 59414.9 Design of Mat Foundations by Elastic Plate Method 59514.10 Floating Foundation 59514.11 Problems 603

CHAPTER 15 DEEP FOUNDATION I:PILE FOUNDATION 605

15.1 Introduction 605

15.2 Classification of Piles 60515.3 Types of Piles According to the Method of Installation 60615.4 Uses of Piles 60815.5 Selection of Pile 60915.6 Installation of Piles 610

PART A-VERTICAL LOAD BEARING CAPACITY OF A SINGLE VERTICAL PILE 61315.7 General Considerations 61315.8 Methods of Determining Ultimate Load Bearing Capacity of a

Single Vertical Pile 61715.9 General Theory for Ultimate Bearing Capacity 61815.10 Ultimate Bearing Capacity in Cohesionless Soils 62015.11 Critical Depth 62115.12 Tomlinson's Solution for Qb in Sand 62215.13 Meyerhof's Method of Determining Qbfor Piles in Sand 62415.14 Vesic's Method of Determining Qb 62515.15 Janbu's Method of Determining Qb 62815.16 Coyle and Castello's Method of Estimating Qb\n Sand 62815.17 The Ultimate Skin Resistance of a Single Pile in Cohesionless Soil 62915.18 Skin Resistance Qf by Coyle and Castello Method (1981) 63115.19 Static Bearing Capacity of Piles in Clay Soil 63115.20 Bearing Capacity of Piles in Granular Soils Based on SPT Value 63515.21 Bearing Capacity of Piles Based on Static Cone Penetration

Tests (CPT) 65215.22 Bearing Capacity of a Single Pile by Load Test 66315.23 Pile Bearing Capacity from Dynamic Pile Driving Formulas 66615.24 Bearing Capacity of Piles Founded on a Rocky Bed 67015.25 Uplift Resistance of Piles 671

Contents xix

PART B-PILE GROUP 67415.26 Number and Spacing of Piles in a Group 67415.27 Pile Group Efficiency 67615.28 Vertical Bearing Capacity of Pile Groups Embedded in

Sands and Gravels 67815.29 Settlement of Piles and Pile Groups in Sands and Gravels 68115.30 Settlement of Pile Groups in Cohesive Soils 68915.31 Allowable Loads on Groups of Piles 69015.32 Negative Friction 69215.33 Uplift Capacity of a Pile Group 69415.34 Problems 696

CHAPTER 16 DEEP FOUNDATION II:BEHAVIOR OF LATERALLY LOADED VERTICAL ANDBATTER PILES 699

16.1 Introduction 699

16.2 Winkler's Hypothesis 70016.3 The Differential Equation 70116.4 Non-dimensional Solutions for Vertical Piles Subjected to

Lateral Loads 70416.5 p-y Curves for the Solution of Laterally Loaded Piles 70616.6 Broms' Solutions for Laterally Loaded Piles 70916.7 A Direct Method for Solving the Non-linear Behavior of

Laterally Loaded Flexible Pile Problems 71616.8 Case Studies for Laterally Loaded Vertical Piles in Sand 72216.9 Case Studies for Laterally Loaded Vertical Piles in Clay 72516.10 Behavior of Laterally Loaded Batter Piles in Sand 73116.11 Problems 739

CHAPTER 17 DEEP FOUNDATION III:DRILLED PIER FOUNDATIONS 741

17.1 Introduction 741

17.2 Types of Drilled Piers 74117.3 Advantages and Disadvantages of Drilled Pier Foundations 74317.4 Methods of Construction 74317.5 Design Considerations 75117.6 Load Transfer Mechanism 75217.7 Vertical Bearing Capacity of Drilled Piers 75417.8 The General Bearing Capacity Equation for the Base Resistance

«. (= O 755

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17.9 Bearing Capacity Equations for the Base in Cohesive Soil 75617.10 Bearing Capacity Equation for the Base in Granular Soil 75617.11 Bearing Capacity Equations for the Base in Cohesive IGM or Rock 75917.12 The Ultimate Skin Resistance of Cohesive and

Intermediate Materials 76017.13 Ultimate Skin Resistance in Cohesionless Soil and Gravelly Sands 76317.14 Ultimate Side and Total Resistance in Rock 76417.15 Estimation of Settlements of Drilled Piers at Working Loads 76517.16 Uplift Capacity of Drilled Piers 77717.17 Lateral Bearing Capacity of Drilled Piers 77917.18 Case Study of a Drilled Pier Subjected to Lateral Loads 78717.19 Problems 787

CHAPTER 18 FOUNDATIONS ON COLLAPSIBLE ANDEXPANSIVE SOILS 791

18.1 General Considerations 791

PART A-COLLAPSIBLE SOILS 79318.2 General Observations 79318.3 Collapse Potential and Settlement 79518.4 Computation of Collapse Settlement 79618.5 Foundation Design 79918.6 Treatment .Methods for Collapsible Soils 800

PART B-EXPANSIVE SOILS 80018.7 Distribution of Expansive Soils 80018.8 General Characteristics of Swelling Soils 80118.9 Clay Mineralogy and Mechanism of Swelling 80318.10 Definition of Some Parameters 80418.11 Evaluation of the Swelling Potential of Expansive Soils by Single

Index Method 80418.12 Classification of Swelling Soils by Indirect Measurement 80618.13 Swelling Pressure by Direct Measurement 81218.14 Effect of Initial Moisture Content and Initial Dry Density on

Swelling Pressure 81318.15 Estimating the Magnitude of Swelling 81418.16 Design of Foundations in Swelling Soils 81718.17 Drilled Pier Foundations 81718.18 Elimination of Swelling 82718.19 Problems 828

Contents xxi

CHAPTER 19 CONCRETE AND MECHANICALLY STABILIZEDEARTH RETAINING WALLS 833

PART A-CONCRETE RETAINING WALLS 83319.1 Introduction 83319.2 Conditions Under Which Rankine and Coulomb Formulas Are

Applicable to Retaining Walls Under the Active State 83319.3 Proportioning of Retaining Walls 83519.4 Earth Pressure Charts for Retaining Walls 83619.5 Stability of Retaining Walls 839

PART B-MECHANICALLY STABILIZED EARTH RETAINING WALLS 84919.6 General Considerations 84919.7 Backfill and Reinforcing Materials 85119.8 Construction Details 85519.9 Design Considerations for a Mechanically Stabilized Earth Wall 85719.10 Design Method 85919.11 External Stability 86319.12 Examples of Measured Lateral Earth Pressures 87519.13 Problems 877

CHAPTER 20 SHEET PILE WALLS AND BRACED CUTS 88120.1 Introduction 88120.2 Sheet Pile Structures 88320.3 Free Cantilever Sheet Pile Walls 88320.4 Depth of Embedment of Cantilever Walls in Sandy Soils 88520.5 Depth of Embedment of Cantilever Walls in Cohesive Soils 89620.6 Anchored Bulkhead: Free-Earth Support Method—Depth of

Embedment of Anchored Sheet Piles in Granular Soils 90820.7 Design Charts for Anchored Bulkheads in Sand 91320.8 Moment Reduction for Anchored Sheet Pile Walls 91620.9 Anchorage of Bulkheads 92520.10 Braced Cuts 93120.11 Lateral Earth Pressure Distribution on Braced-Cuts 93520.12 Stability of Braced Cuts in Saturated Clay 93820.13 Bjerrum and Eide Method of Analysis 94020.14 Piping Failures in Sand Cuts 94520.15 Problems 945

XXII Contents

CHAPTER 21 SOIL IMPROVEMENT21.1 Introduction21.2 Mechanical Compaction21.3 Laboratory Tests on Compaction21.4 Effect of Compaction on Engineering Behavior21.5 Field Compaction and Control21.6 Compaction for Deeper Layers of Soil21.7 Preloading21.8 Sand Compaction Piles and Stone Columns21.9 Soil Stabilization by the Use of Admixtures21.10 Soil Stabilization by Injection of Suitable Grouts21.11 Problems

APPENDIX A SI UNITS IN GEOTECHNICAL ENGINEERING

APPENDIX B SLOPE STABILITY CHARTS AND TABLES

REFERENCES

INDEX

951951

952

953

959

962

973

974

980

981

983

983

987

993

1007

1025