Soils and Foundations Reference Manual Vol II

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Soils and Foundations Reference Manual Vol II

Soils and Foundations
Reference Manual Vol. II
Naresh C. Samtani*, PE, PhD
Edward A. Nowatzki*, PE, PhD

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Soils and Foundations II
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Preface

Since the primary purpose of this manual is to provide a concise treatment of the fundamental concepts in soil mechanics and an introduction to the practical design of various geotechnical features related to highway construction, the details of the theory underlying the methods of analysis have been largely omitted in favor of discussions on the application of those theories to geotechnical problems. Some exceptions to this general approach were made. For example, the concepts of lateral earth pressure and bearing capacity rely too heavily on a basic understanding of the Mohr’s circle for stress for a detailed presentation of the Mohr’s circle theory to be omitted. However, so as not to encumber the text, the basic theory of the Mohr’s circle is presented in Appendix B for the reader’s convenience and as an aid for the deeper understanding of the concepts of earth pressure and bearing capacity.

TOC

8.0 SHALLOW FOUNDATIONS .. 8-1
8.01 Prim ary References . 8-1
8.1 GENERAL APPROACH TO FOUNDATION DESIGN .. 8-1
8.1.1 Foundation Alternatives and Cost Evaluation .. 8-2
8.1.2 Loads and Limit States for Foundation Design 8-3
8.2 TYPES OF SHALLOW FOUNDATIONS 8-4
8.2.1 Isolated Spread Footings . 8-4
8.2.2 Continuous or Strip Footings. 8-6
8.2.3 Spread Footings with Cantilevered Stemwalls . 8-7
8.2.4 Bridge Abutments 8-7
8.2.5 Retaining Structures 8-9
8.2.6 Building Foundations. 8-9
8.2.7 Combined Footings . 8-9
8.2.8 Mat Foundations 8-11
8.3 SPREAD FOOTING DESIGN CONCEPT AND PROCEDURE 8-12
8.4 BEARING CAPACITY . 8-15
8.4.1 Failure Mechanisms . 8-16
8.4.1.1 General Shear .. 8-16
8.4.1.2 Local Shear .. 8-18
8.4.1.3 Punching Shear .. 8-18
8.4.2 Bearing Capacity Equation Formulation .. 8-18
8.4.2.1 Comparative Effect of Various Terms in Bearing Capacity Formulation . 8-22
8.4.3 Bearing Capacity Correction Factors.. 8-23
8.4.3.1 Footing Shape (Eccentricity and Effective Dimensions).. 8-24
8.4.3.2 Location of the Ground Water Table .. 8-27
8.4.3.3 Embedment Depth 8-28
8.4.3.4 Inclined Base 8-29
8.4.3.5 Inclined Loading 8-29
8.4.3.6 Sloping Ground Surface. 8-30
8.4.3.7 Layered Soils .. 8-30
8.4.4 Additional Considerations Regarding Bearing Capacity Correction Factors. 8-32
8.4.5 Local or Punching Shear 8-33
8.4.6 Bearing Capacity Factors of Safety . 8-35
8.4.6.1 Overstress Allowances 8-35
8.4.7 Practical Aspects of Bearing Capacity Formulations . 8-36
8.4.7.1 Bearing Capacity Computations 8-36
8.4.7.2 Failure Zones .. 8-38
8.4.8 Presum ptive Bearing Capacities 8-40
8.4.8.1 Presumptive Bearing Capacity in Soil 8-40
8.4.8.2 Presumptive Bearing Capacity in Rock . 8-40
8.5 SETTLEMENT OF SPREAD FOOTINGS. 8-44
8.5.1 Imme diate Settlement . 8-44
8.5.1.1 Schmertmann’s Modified Method for Calculation of Immediate Settlements 8-45
8.5.1.2 Comments on Schmertmann’s Method.. 8-47
8.5.1.3 Tabulation of Parameters in Schmertmann’s Method 8-52
8.5.2 Obtaining Limiting Applied Stress for a Given Settlement. 8-54
8.5.3 Consolidation Settlement .. 8-54
8.6 SPREAD FOOTINGS ON COMPACTED EMBANKMENT FILLS.. 8-55
8.6.1 Settlement of Footings on Structural Fills 8-57
8.7 FOOTINGS ON INTERMEDIATE GEOMATERIALS (IGMs) AND ROCK . 8-58
8.8 ALLOWABLE BEARING CAPACITY CHARTS 8-60
8.8.1 Comments on the Allowable Bearing Capacity Charts . 8-62
8.9 EFFECT OF DEFORMATIONS ON BRIDGE STRUCTURES. 8-64
8.9.1 Criteria for Tolerable Movements of Bridges. 8-68
8.9.1.1 Vertical Movements. 8-68
8.9.1.2 Horizontal Movements .. 8-69
8.9.2 Loads for Evaluation of Tolerable Movements Using Construction Point Concept . 8-70
8.10 SPREAD FOOTING LOAD TESTS .. 8-72
8.11 CONSTRUCTION INSPECTION .. 8-73
8.11.1 Structural Fill Materials . 8-73
8.11.2 Monitoring 8-75

9.0 DEEP FOUNDATIONS 9-1
9.1 TYPES OF DEEP FOUNDATIONS AND PRIMARY REFERENCES 9-3
9.1.1 Selection of Driven Pile or Cast-in-Place (CIP) Pile Based on Subsurface Conditions .. 9-5
9.1.2 Design and Construction Terminology . 9-5
9.2 DRIVEN PILE DESIGN-CONSTRUCTION PROCESS.. 9-7
9.3 ALTERNATE DRIVEN PILE TYPE EVALUATION. 9-18
9.3.1 Cost Evaluation of Alternate Pile Types 9-19
9.4 COMPUTATION OF PILE CAPACITY. 9-20
9.4.1 Factors of Safety 9-23
9.5 DESIGN OF SINGLE PILES. 9-29
9.5.1 Ultimate Geotechnical Capacity of Single Piles inCohesionless Soils 9-29
9.5.1.1 Nordlund Method.. 9-29
9.5.2 Ultimate Geotechnical Capacity of Single Piles in Cohesive Soils . 9-47
9.5.2.1 Total Stress – α-method. 9-47
9.5.2.2 Effective Stress – β-method . 9-52
9.5.3 Ultimate Geotechnical Capacity of Single Piles in Layered Soils 9-59
9.5.4 Plugging of Open Pile Sections . 9-60
9.5.5 Time Effects on Pile Capacity 9-64
9.5.5.1 Soil Setup .. 9-64
9.5.5.2 Relaxation . 9-65
9.5.6 Additional Design and Construction Considerations.. 9-66
9.5.7 The DRIVEN Computer Program 9-67
9.5.8 Ultimate Capacity of Piles on Rock and in Intermediate Geomaterials (IGMs) .. 9-75
9.6 DESIGN OF PILE GROUPS.. 9-76
9.6.1 Axial Compression Capacity of Pile Groups .. 9-78
9.6.1.1 Cohesionless Soils 9-78
9.6.1.2 Cohesive Soils. 9-79
9.6.1.3 Block Failure of Pile Groups .. 9-81
9.6.2 Settlement of Pile Groups . 9-82
9.6.2.1 Elastic Compression of Piles .. 9-82
9.6.2.2 Settlement of Pile Groups in Cohesionless Soils .. 9-83
9.6.2.3 Settlement of Pile Groups in Cohesive Soils .. 9-84
9.7 DESIGN OF PILES FOR LATERAL LOAD 9-84
9.8 DOWNDRAG OR NEGATIVE SHAFT RESISTANCE 9-87
9.9 CONSTRUCTION OF PILE FOUNDATIONS 9-90
9.9.1 Selection of Design Safety Factor Based on Construction Control . 9-90
9.9.2 Pile Driveability . 9-90
9.9.2.1 Factors Affecting Drivability .. 9-91
9.9.2.2 Driveability Versus Pile Type. 9-93
9.9.3 Pile Driving Equipment and Operation . 9-94
9.9.4 Dynamic Pile Driving Formulae 9-97
9.9.5 Dynamic Analysis of Pile Driving . 9-100
9.9.6 Wave Equation Methodology .. 9-103
9.9.6.1 Input to Wave Equation Analysis .. 9-105
9.9.6.2 Output Values from Wave Equation Analysis . 9-106
9.9.6.3 Pile Wave Equation Analysis Interpretation. 9-106
9.9.7 Driving Stresses .. 9-108
9.9.8 Guidelines for Assessing Pile Drivability.. 9-109
9.9.9 Pile Construction Monitoring Considerations . 9-112
9.9.10 Dynamic Pile Monitoring .. 9-114
9.9.10.1 Applications 9-115
9.9.10.2 Interpretation of Results and Correlation with Static Pile Load Tests . 9-117
9.10 CAST-IN-PLACE (CIP) PILES . 9-119
9.11 DRILLED SHAFTS.. 9-123
9.11.1 Characteristics of Drilled Shafts . 9-124
9.11.2 Advantages of Drilled Shafts 9-125
9.11.1.1 Special Considerations for Drilled Shafts 9-126
9.11.3 Subsurface Conditions and Their Effect on Drilled Shafts 9-126
9.12 ESTIMATING AXIAL CAPACITY OF DRILLED SHAFTS.. 9-127
9.12.1 Side Resistance in Cohesive Soil 9-129
9.12.1.1 Mobilization of Side Resistance in Cohesive Soil .. 9-130
9.12.2 Tip Resistance in Cohesive Soil . 9-131
9.12.2.1 Mobilization of Tip Resistance in Cohesive Soil. 9-131
9.12.3 Side Resistance in Cohesionless Soil 9-132
9.12.3.1 Mobilization of Side Resistance in Cohesionless Soil .. 9-133
9.12.4 Tip Resistance in Cohesionless Soil . 9-133
9.12.4.1 Mobilization of Tip Resistance in Cohesionless Soil. 9-134
9.12.5 Determination of Axial Shaft Capacity in Layered Soils or Soils with Varying Strength with Depth. 9-136
9.12.6 Group Action, Group Settlement, Downdrag and Lateral Loads .. 9-136
9.12.7 Estimating Axial Capacity of Shafts in Rocks. 9-140
9.12.7.1 Side Resistance in Rocks.. 9-140
9.12.7.2 Tip Resistance in Rocks 9-141
9.12.8 Estimating Axial Capacity of Shafts in Intermediate GeoMaterials (IGM’s) . 9-142
9.13 CONSTRUCTION METHODS FOR DRILLED SHAFTS. 9-142
9.14 QUALITY ASSURANCE AND INTEGRITY TESTING OF DRILLED SHAFTS.. 9-146
9.14.1 The Standard Crosshole Sonic Logging (CSL) Test 9-146
9.14.2 The Gamma Density Logging (GDL) Test 9-149
9.14.3 Selecting the Type of Integrity Test for Quality Assurance . 9-152
9.15 STATIC LOAD TESTING FOR DEEP FOUNDATIONS.. 9-153
9.15.1 Reasons for Load Testing .. 9-153
9.15.2 Advantages of Static Load Testing 9-153
9.15.3 When to Load Test . 9-154
9.15.4 Effective Use of Load Tests.. 9-156
9.15.4.1 Design Stage .. 9-156
9.15.4.2 Construction Stage .. 9-156
9.15.5 Prerequisites for Load Testing. 9-157
9.15.6 Developing a Static Load Test Program . 9-158
9.15.7 Compression Load Tests. 9-158
9.15.7.1 Compression Test Equipment 9-160
9.15.7.2 Recommended Compression Test Loading Method .. 9-165
9.15.7.3 Presentation and Interpretation of Compression Test Results . 9-165
9.15.7.4 Plotting the Failure Criteria 9-166
9.15.7.5 Determination of the Ultimate (Failure) Load .. 9-167
9.15.7.6 Determination of the Allowable Geotechnical Load . 9-168
9.15.7.7 Load Transfer Evaluations .. 9-168
9.15.8 Other Compression Load Tests 9-171
9.15.8.1 The Osterberg Cell Method 9-171
9.15.8.2 Statnamic Test Method . 9-176
9.15.9 Limitations of Compression Load Tests . 9-179
9.15.10Axial Tension and Lateral Load Tests . 9-179

10.0 EARTH RETAINING STRUCTURES .. 10-1
10.01 Primary References .. 10-4
10.1 CLASSIFICATION OF EARTH RETAINING STRUCTURES 10-4
10.1.1 Classification by Load Support Mechanism 10-4
10.1.2 Classification by Construction Method . 10-6
10.1.3 Classification by System Rigidity. 10-7
10.1.4 Temporary and Permanent Wall Applications 10-7
10.1.5 Wall Selection Considerations 10-8
10.2 LATERAL EARTH PRESSURES .. 10-8
10.2.1 At-Rest Lateral Earth Pressure 10-10
10.2.2 Active and Passive Lateral Earth Pressures.. 10-12
10.2.3 Effect of Cohesion on Lateral Earth Pressures 10-16
10.2.4 Effect of Wall Friction and Wall Adhesion on Lateral Earth Pressures. 10-16
10.2.5 Theoretical Lateral Earth Pressures in Stratified Soils 10-23
10.2.6 Semi Empirical Lateral Earth Pressure Diagrams . 10-24
10.2.7 Lateral Earth Pressures in Cohesive Backfills. 10-24
10.3 LATERAL PRESSURES DUE TO WATER.. 10-27
10.4 LATERAL PRESSURE FROM SURCHARGE LOADS. 10-29
10.4.1 General. 10-29
10.4.2 Uniform Surcharge Loads .. 10-31
10.4.3 Point, Line, and Strip Loads . 10-31
10.5 WALL DESIGN . 10-35
10.5.1 Steps 1, 2, and 3 – Established Project Requirements, Subsurface Conditions, Design Parameters .. 10-36
10.5.2 Step 4 – Select Base Dimension Based on Wall Height . 10-37
10.5.3 Step 5 – Select Lateral Earth Pressure Distribution.. 10-37
10.5.4 Step 6 – Evaluate Bearing Capacity . 10-41
10.5.4.1 Shallow Foundations .. 10-41
10.5.4.2 Deep Foundations . 10-42
10.5.5 Step 7 – Evaluate Overturning and Sliding .. 10-43
10.5.6 Step 8 – Evaluate Global Stability. 10-44
10.5.7 Step 9 – Evaluate Settlement and Tilt.. 10-45
10.5.8 Step 10 – Design Wall Drainage Systems . 10-45
10.5.8.1 Subsurface Drainage 10-46
10.5.8.2 Drainage System Components .. 10-48
10.5.8.3 Surface Water Runoff. 10-50
10.6 EXTERNAL STABILITY ANALYSIS OF A CIP CANTILEVER WALL .. 10-52
10.7 CONSTRUCTI ON INSPECTION .10.56

11.0 GEOTECHNICAL REPORTS . 11-1
11.01 Primary References .. 11-1
11.1 TYPES OF REPORTS 11-1
11.1.1 Geotechnical Investigation Reports . 11-2
11.1.2 Geotechnical Design Reports.. 11-3
11.1.3 GeoEnvironmental Reports.. 11-6
11.2 DATA PRESENTATION. 11-7
11.2.1 Boring Logs . 11-7
11.2.2 Boring Location Plans 11-8
11.2.3 Subsurface Profiles .. 11-9
11.3 TYPICAL SPECIAL CONTRACT NOTES 11-11
11.4 SUBSURFACE INFORMATION MADE AVAILABLE TO BIDDERS 11-14
11.5 LIMITATIONS (DISCLAIMERS) .. 11-15