Piles and Pile Foundations

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1 Piles and Pile Foundations Carlo Viggiani, Alessandro Mandolini and Gianpiero Russo * j \ Spon Press an imprint of Taylor & Francis LONDON AND NEWYORK

2 Contents List of illustrations Introduction PART I General 1 Drained and undrained conditions; total and effective stress analysis 1.1 Stress and pore pressure Permeability and seepage Principle of effective stress Consolidation Some examples In situ stress Piping Onedimensional consolidation Undrained conditions: analysis in terms of total stress Equivalence of the analysis in terms of total and effective stress in undrained conditions 17 2 Review of pile types 2.7 Introduction Replacement piles General Percussion boring Rotary boring Continuous flight auger piles Micropiles Displacement piles Driving equipment Prefabricated driven piles Cast in situ driven piles 41

3 ULS SLS viii Contents Displacement screw piles Partial displacement piles Driven H or tubular piles Large stem auger piles (PressoDrill, SVB) Advantages and shortcomings of the different pile types 49 3 Design issues 3.1 The steps of design Overall factor of safety Limit state design Introduction Ultimate Limit State Serviceability limit state PART II Present practice of piled foundations design under vertical loads 4 Bearing capacity under vertical load 4.1 Introduction Definition of bearing capacity Bearing capacity from fundamental soil properties Medium diameter piles; base resistance Medium diameter piles; shaft resistance Large diameter bored piles Micropiles Bearing capacity from correlation with penetrometer data CPT SPT Driving formulas The wave equation analysis Bearing capacity of pile groups Rock socketed piles Introduction Shaft resistance Base resistance 84 5 Settlement 5.1 Introduction Settlement of the single pile Empirical methods Load transfer curves Elastic continuum: simplified analytical solution Elastic continuum: solutions by BEM Solutions by FEM 105

4 Contents ix 5.3 Settlement of pile groups Empirical methods Equivalent raft and equivalent pier Elastic continuum Evaluation of soil properties and implementation of the analysis Nonlinearity Differential settlement Soilstructure interaction and the design of pile cap Introduction Design of the cap of small pile groups Design of the raft for large pile groups; Introduction FEM analysts of the raft 136 the code NAPRA Closed form solution for soil displacements Piles as nonlinear interacting springs Interaction between piles and raft elements Solution procedure Influence of the finite stiffness ofthe cap Influence of cap in contact and nonlinearity of the piles Influence of creep Concluding remarks Pile testing Vertical load tests General Test equipment Test procedure Test interpretation Qsterberg cell test Dynamic load test Introduction Experimental layout Dynamic tests and stress wave theory Results and interpretation Concluding remarks Horizontal load test Introduction Equipment and procedure Interpretation 174

5 x Contents PART III Present practice of piled foundations design under horizontal loads Bearing capacity under horizontal load Introduction Bearing capacity of the single pile General Freehead pile, cohesive soils Fixedhead pile, cohesive soils Freehead pile, cohesionless soils Fixedhead pile, cohesionless soils Miscellaneous Bearing capacity of the pile group Displacements and bending moments Single pile Experimental evidence Winkler linear spring model Nonlinear springs (p y curves) Characteristic load method Boundary Element Method Maximum bending moment Finite Element Method Pile groups Experimental evidence Methods of analysis 228 PART IV Analysis and design of piled rafts Piled rafts Introduction Vertical bearing capacity Settlement Introduction Small rafts Large rafts Horizontal load Raft foundations with disconnected piles 258 References 260 Index 2.73

Cavity Expansion Methods in Geomechanics

Cavity Expansion Methods in Geomechanics by Hai-Sui Yu School of Civil Engineering, University of Nottingham, U. K. KLUWER ACADEMIC PUBLISHERS DORDRECHT / BOSTON / LONDON TABLE OF CONTENTS Foreword Preface