Soils and Foundations for Architects and Engineers Soils and Foundations for Architects and Engineers Chester I. Duncan, Jr., FASCE Professor of Architecture The University of Texas at Arlington RUf?TURA~ I ngmeermg s e r e s 1 ~SPRINGER SCIENCE+BUSINESS MEDIA, LLC Copyright © 1992 by Springer Science+ Business Media New York Originally published by Van Nostrand Reinhold in 1992 Library of Congress Catalog Card Number 91-33800 ISBN 978-1-4757-6547-2 ISBN 978-1-4757-6545-8 (eBook) DOI 10.1007/978-1-4757-6545-8 All rights reserved. No part of this work covered by the copyright hereon may be reproduced or used in any form or by any means-graphic, electronic, or mechanical, including photocopying, recording, taping, or information storage and retrieval systems-without written permission of the publisher. Library of Congress Cataloging-in-Publication Data Duncan, Jr., Chester 1., 1925- Soils and foundations for architects and engineers I Chester I. Duncan, Jr. p. em. Includes index. ISBN 978-1-4757-6547-2 1. Soil mechanics. 2. Foundations. I. Title. TA710.D865 1992 624.1 '5136--dc20 91-33800 CIP ACKNOWLEDGMENT Artwork prepared by Sherry Leigh Penley The University of Texas at Arlington Contents Preface XV A Brief Overview of Chapter Content xvii 1 CLASSIFICATION OF SOILS 1 1-1. General 1 1-2. Soil Terminology 1 Rock, Soil, Coarse Grained Soils, Fine Grained Soils, Gravel, Sand, Silt, Clay, Colloids, Organic Soil, Inorganic Soil, Loam, Top Soil, Consistency, Cohesion, Plasticity, Atterberg Limits 1-3. Soil Classification 4 General, Classification Systems 1-4. Particle Size 5 General, Sieve Test, Classification by Particle Size, Limitation to Classification by Particle Size 1-5. Particle Distribution 8 General, Different Kinds of Particle Distribution, Coefficients of Uniformity and Curvature, Sedimentation Test 1-6. Soil Classification by Texture 11 1-7. AASHO Classification System 12 1-8. ASTM Classification System 13 1-9. The Unified Soil Classification System 13 General, The Fifteen Soil Classifications, Identification of Organic Soils, Identification oflnorganic Soils, Plasticity Chart 1-10. Closure 19 1-11. Sample Problems 20 2 PHYSICAL PROPERTIES OF SOILS 27 2-1. General 27 2-2. Unit Weight, Density 29 2-3. Porosity 30 2-4. Void Ratio 30 vu Vlll Contents 2-5. Water Content 31 2-6. Specific Gravity 31 2-7. Representative Values of Physical Properties 32 2-8. Relative Density of Coarse Grained Soils 33 2-9. Angle of Internal Friction 35 2-10. Unconfined Compression Strength 36 2-11. Consistency 38 2-12. Cohesion 38 2-13. Sensitivity 38 2-14. Sample Problems 40 3 SUBSURFACE SOIL EXPLORATION 46 3-1. Preliminary Investigation of Site 46 General Considerations, Portable Sampling Equipment, Soil Examination by Test Pit 3-2. Preliminary Identification of Soils 50 Touch Test, Dry Strength Test, Shaking Test, Thread Test, Dispersion Test, Representative Test Results 3-3. Field Survey 51 3-4. Engineering Investigation 52 Laboratory Tests 3-5. Test Borings 54 General, Earth Core Borings, Standard Penetration Test, Depth to Bedrock, Refusal, Water Table, Perforated Pipe 3-6. Typical Test Boring Log 58 3-7. Core Borings 58 3-8. Geologic Description of Site 62 3-9. Shear Tests 63 Vane Shear Field Test, Direct Shear Laboratory Test, Triaxial Compression Test 3-10. Closure 67 4 ALLOWABLE SOIL BEARING PRESSURE 68 4-1. General Design Considerations 68 4-2. Soil Behavior at Ultimate Bearing Capacity 69 4-3. Equations for Ultimate Bearing Capacity 70 General Considerations, Footings on Mixed Grained Soil, Footings on Granular Soil, Footings on Cohesive Soil 4-4. Allowable Soil Bearing Pressure 73 4-5. Pressure Distribution-Pressure Bulbs 74 Footing Overlap 4-6. Effect of Ground Water on Ultimate Bearing Capacity 76 4-7. General Considerations of Settlement 76 Reasons for Settlement on Sand, Reasons for Settlement of Clay, Rate of Settlement, Permissible Settlement Contents ix 4-8. Settlement Calculations-Footings on Sand 80 Modification in Blow Count Due to Ground Water, Modification in Blow Count Due to Release of Overburden 4-9. Recommendations for Design of Footings on Sand 83 4-10. The Theory of Settlement-Footings on Oay 87 Overburden, Normally Loaded Soils, Preloaded Soils, Reduction in Void Ratio as a Function of Pressure, Settlement as a Function of Reduction in Void Ratio 4-11. Consolidation Test 89 Deformation as a Function of Time, Thee-Log p Curve 4-12. Settlement Calculations-Footings on Clay 93 The Formula For Settlement, Simplified Calculations For Ap, Settlement Calculation Procedure, The Effect of Site Excavation 4-13. Recommendations for Design of Footings on Clay 96 4-14. Recommendations for Design of Footings on Mixed grained Soil 97 4-15. Closing Recommendations 98 General, Minimum Soil Pressure, Local Shear, Support Options, Minimum Footing Width 4-16. Presumptive Bearing Pressure 100 4-17. Sample Problems 101 5 SPREAD FOOTINGS 117 5-1. General 117 5-2. Footing Excavation 117 Earth Formed Footings, Wood Formed Footings 5-3. Approval of Subgrade 119 5-4. Interaction Between Footing and Ground 119 5-5. Typical Footing Reinforcement 120 5-6. Vertical Dowels 121 Column Dowels, Wall Dowels, Requirements Relating to Dowels 5-7. Typical Footing Details 122 Purpose, Wall Footings, Individual Column Footings, Combined Footings, Required Footing Area, Mat Foundations 5-8. Property Line Considerations 125 Rectangular Footings, Strap Footings, Combined Footings 5-9. Factors Affecting Vertical Placement of Footings 128 Acceptable Soil Bearing Pressure, Placement With Respect to Frost, Placement With Respect to Expansive Soil, Proximity to Adjacent Footings, Proximity To Adjacent Properties, Effect of Ground Water 5-10. Dead Load Bearing Pressure 132 5-11. Sample Problems 132 X Contents 6 PILES, PIERS AND CAISSONS 137 6-1. General 137 6-2. Piles 137 Timber Piles, Structural Steel HP Piles, Steel Shell Piles, Steel Pipe 6-3. Piers 144 Installation in Clay, Installation in Sand, With Slurry, Installation in Sand, With Hollow Shaft Auger 6-4. Caissons 147 6-5. Ultimate Load Carrying Capacity 150 6-6. Unit Shear Stress Due to Cohesion-Clay 152 6-7. Unit Shear Stress Due to Skin Friction-Sand 153 6-8'. Unit End Bearing Stress-Clay 154 6-9. Unit End Bearing Stress-Sand 155 6-10. Evaluation of Design by Formula 156 6-11. Load Tests 156 Load Test Scheduling, General Requirements, Testing Procedures, Test Evaluation, Safety Factors 6-12. Pile Clusters 160 Load Capacity, Minimum Number of Piles 6-13. Battered Piles 162 6-14. Advantages and Disadvantages 162 Piles, Piers, Caissons 6-15. Appropriate Use of Piles, Piers and Caissons 164 6-16. Concreting With Tremie or Elephant Trunk 165 6-17. Sample Problems 166 7 LATERAL EARTH PRESSURE 178 7-1. General 178 7-2. The Concept of Lateral Earth Pressure 178 Angle of Repose(), Angle of Rupture a, Angle of Internal Friction~ 7-3. The Coulomb Equation for Shear Resistance 181 7-4. The Concept of Active Earth Pressure 182 7-5. The Wedge Theory of Active Earth Pressure 183 7-6. Coefficient of Active Pressure 185 7-7. Validity of the Active Pressure Formulas 187 7-8. Equivalent Liquid Pressure Theory 187 7-9. Numerical Accuracy of"Ka and Pa 189 7-10. Charts for Estimating Backfill Pressure 190 7-11. Sample Problems 191 8 WALLS-CONSTRUCTION DETAILS 196 8-1. General 196 8-2. Earth Embankment 197 Contents xi 8-3. Sheet Piling Retaining Walls 197 8-4. Soldier Beam Retaining Walls 200 8-5. Basement Wall-Typical Detail 202 8-6. Basement Wall-Special Conditions 204 Face Brick Below Grade, Exposed Concrete Wall, Recessed Entrance, First Floor Slab Extension, Basement Wall Bearing on a Continuous Footing, Basement Wall Designed as a Grade Beam 8-7. Gravity Retaining Walls 209 8-8. Cantilever Retaining Wall 210 8-9. Wails Requiring Special Restraints 211 Battered Piles, Prestressed Tiedowns, Prestressed Tiebacks 8-10. Prestressed Tiedowns and Tiebacks 214 Purpose, Material, Installation, Protection of Cables, Destruction Tests 8-11. Requirements Relative to Backfill 218 Material Source, Factors in the Selection and Use of Backfill, Use of Granular Materials, Use of Cohesive Materials, Installation of Backfi.ll, Design Responsibility 8-12. Drainage 222 General, Drainage System-Basement Wall, Drainage System -Cantilever Retaining Wall, Drainage System- Gravity Retaining Wall, Drainage Filter Design 8-13. Sample Problems 225 9 WALLS-DESIGN CONSIDERATIONS 228 9-1. Lateral Pressure Design Requirements 228 General, Lateral Pressure as a Function of Excavation, Concerns Regarding Water Pressure 9-2. Basement Wall Design Options 231 Wails Designed to Span Vertically, Wails Designed to Span Horizontally, General Details of Reinforcement, Evaluation of Design Options, A Special Word of Caution 9-3. Cantilever Retaining Wall-Modes of Failure 236 ·Overturning Mode, Sliding Mode 9-4. Cantilever Retaining Walls-Different Types 237 Type 1, Type 2, Type 3, General Proportions 9-5. Typical Reinforcing-Cantilever Retaining Wall 239 9-6. Counterfort Retaining Walls 240 9-7. Earth Pressure Transfer-Concrete to Concrete 241 General, Types 1 and 2, Type 3 9-8. Earth Pressure Transfer-Footing to Ground 243 General, Resistance Developed by Shear, Resistance Developed by Passive Pressure, Safety Factor Against Lateral Movement