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Boca Raton London New York Washington, D.C.CRC Press
SHALLOW FOUNDATIONSBearing Capacity and SettlementBearing Capacity and Settlement
Braja M. Das
PREFACE
Shallow Foundations: Bearing Capacity and Settlement is intended for use asa reference book by university faculty members and graduate students in thearea of geotechnical engineering as well as by consulting engineers.
The text is divided into eight chapters. Chapters 2, 3, and 4 present thevarious theories developed during the past fifty years for estimating the ultimatebearing capacity of shallow foundations under various types of loading andsubsoil conditions.
Chapter 5 discusses the principles for estimating the settlement offoundations—both elastic and consolidation. In order to calculate the founda-tion settlement, it is desirable to know the principles for estimating the stressincrease in a soil mass supporting a foundation which carries the load trans-mitted from the superstructure. These principles are also discussed in thisChapter 5. Recent developments regarding the ultimate bearing capacity ofshallow foundations due to earthquake loading are presented in Chapter 6. Alsoincluded in Chapter 6 are some details regarding the permanent founda-tionsettlement due to cyclic and transient loading derived from experimentalobservations obtained from laboratory and field tests.
During the past fifteen years, steady progress has been made to evaluatethe possibility of using reinforcement in soil to increase the ultimate andallowable bearing capacities of shallow foundations and also to reduce theirsettlement under various types of loading conditions. The reinforcementmaterials include galvanized steel strips, geotextile, and geogrid. Chapter 7presents the state-of-the-art on this subject.
Shallow foundations (such as transmission tower foundations) are, onsome occasions, subjected to uplifting forces. The theories relating to the esti-mation of the ultimate uplift capacity of shallow foundations in granular andclay soils are presented in Chapter 8.
Example problems to illustrate the theories are given in each chapter.I am grateful to my wife, Janice, for typing the manuscript in camera-
ready form and preparing the necessary artwork. It will be satisfying to knowfrom the users of the text if it serves the intended purpose.
Braja M. DasSacramento, California
CONTENTS
ONE INTRODUCTION 1.1 Shallow Foundations—General 1.2 Types of Failure in Soil at Ultimate Load 1.3 Settlement at Ultimate Load 1.4 Ultimate and Allowable Bearing Capacities References
TWO ULTIMATE BEARING CAPACITY THEORIES—CENTRIC VERTICAL LOADING 2.1 Introduction 2.2 Terzaghi’s Bearing Capacity Theory 2.3 Terzaghi’s Bearing Capacity Theory for
Local Shear Failure2.4 Meyerhof’s Bearing Capacity Theory 2.5 General Discussion on the Relationships
of Bearing Capacity Factors 2.6 Other Bearing Capacity Theories 2.7 Scale Effects on Bearing Capacity 2.8 Effect of Water Table 2.9 General Bearing Capacity Equation 2.10 Effect of Soil Compressibility 2.11 Bearing Capacity of Foundations on
Anisotropic Soil 2.12 Allowable Bearing Capacity With Respect
to Failure 2.13 Interference of Continuous Foundations in
Granular SoilReferences
THREE ULTIMATE BEARING CAPACITY UNDERINCLINED AND ECCENTRIC LOADS 3.1 Introduction
FOUNDATIONS SUBJECTED TO INCLINED LOAD
3.2 Meyerhof’s Theory (Continuous Foundation)3.3 General Bearing Capacity Equation 3.4 Other Results For Foundations With Centric
Inclined Load 3.5 Continuous Foundation With Eccentric Load3.6 Ultimate Load on Rectangular Foundations References
FOUR SPECIAL CASES OF SHALLOW FOUNDATIONS 4.1 Introduction4.2 Foundation Supported by a Soil With a Rigid
Rough Base at a Limited Depth 4.3 Foundation on Layered Saturated Anisotropic
Clay 4.4 Foundation on Layered c– Soil—Stronger Soil
Underlain by Weaker Soil 4.5 Foundation on Layered c– Soil—Weaker Soil
Underlain by a Stronger Soil 4.6 Continuous Foundation on Weak Clay With a
Granular Trench4.7 Shallow Foundations Above a Void4.8 Foundations on a Slope4.9 Foundations on Top of a Slope References
FIVE SETTLEMENT AND ALLOWABLE BEARINGCAPACITY 5.1 Introduction5.2 Stress Increase in Soil Due to Applied Load
ELASTIC SETTLEMENT
5.3 Flexible and Rigid Foundations 5.4 Settlement Under a Circular Area 5.5 Settlement Under a Rectangular Area5.6 Effect of a Rigid Base at a Limited Depth 5.7 Effect of Depth of Embedment 5.8 Elastic Parameters 5.9 Settlement of Foundations on Saturated Clay5.10 Settlement of Foundations on Sand 5.11 Field Plate Load Tests
CONSOLIDATION SETTLEMENT
5.12 General Principles of Consolidation Settlement 5.13 Relationships for Primary Consolidation
Settlement Calculation 5.14 Three-Dimensional Effect on Primary
Consolidation Settlement 5.15 Secondary Consolidation Settlement
DIFFERENTIAL SETTLEMENT
5.16 General Concepts of Differential Settlement 5.17 Limiting Values of Differential Settlement
ParametersReferences
SIX DYNAMIC BEARING CAPACITY AND SETTLEMENT 6.1 Introduction
( ! = 0) !
!
6.2 Effect of Load Velocity on Ultimate Bearing Capacity
6.3 Ultimate Bearing Capacity Under Earthquake Loading
6.4 Settlement of Foundations on Granular SoilDue to Earthquake Loading
6.5 Foundation Settlement Due to Cyclic Loading—Granular Soil
6.6 Foundation Settlement Due to Cyclic Loading in Saturated Clay
6.7 Settlement Due to Transient Load on FoundationReferences
SEVEN SHALLOW FOUNDATIONS ON REINFORCED SOIL7.1 Introduction
FOUNDATIONS ON METALLIC STRIP-REINFORCED
GRANULAR SOIL
7.2 Failure Mode7.3 Force in Reinforcement Ties7.4 Factor of Safety Against Tie Breaking
and Tie Pullout7.5 Design Procedure for a Continuous Foundation
FOUNDATIONS ON GEOTEXTILE-REINFORCED SOIL
7.6 Laboratory Model Test Results 7.7 Comments on Geotextile Reinforcement
FOUNDATIONS ON GEOGRID-REINFORCED SOIL
7.8 General Parameters 7.9 Relationships for Critical Nondimensional
Parameters for Foundations on Geogrid-Reinforced Sand
7.10 Relationship Between BCRu and BCRs in Sand 7.11 Critical Nondimensional Parameters for
Foundations on Geogrid-Reinforced Clay ( = 0 condition)
7.12 Bearing Capacity Theory 7.13 Settlement of Foundations on Geogrid-
Reinforced Soil Due to Cyclic Loading 7.14 Settlement Due to Impact Loading References
EIGHT UPLIFT CAPACITY OF SHALLOW FOUNDATIONS 8.1 Introduction
FOUNDATIONS IN SAND
8.2 Balla’s Theory8.3 Theory of Meyerhof and Adams
!
8.4 Theory of Vesic 58.5 Saeedy’s Theory 8.6 Discussion of Various Theories 8.7 Effect of Backfill on Uplift Capacity
FOUNDATIONS IN SATURATED CLAY
( = 0 CONDITION) 8.8 Ultimate Uplift Capacity—General 8.9 Vesic’s Theory 8.10 Meyerhof’s Theory 8.11 Modifications to Meyerhof’s Theory 8.12 Factor of SafetyReferences
APPENDIX Conversion Factors
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