Earth Anchors, Second Edition

345 Pages·2013·7.59 MB·English

by  Das

earth
anchors
second edition
Braja M. Das
sanjay Kumar shukla
Copyright © 2013 by J. Ross Publishing, Inc.
ISBN 978-1-60427-077-8
Printed and bound in the U.S.A. Printed on acid-free paper
10 9 8 7 6 5 4 3 2 1
Library of Congress Cataloging-in-Publication Data
Das, Braja M., 1941-
Earth anchors / by Braja M. Das and Sanjay Kumar Shukla. — Second
edition.
pages cm
Includes bibliographical references and index.
ISBN 978-1-60427-077-8 (hardcover : alk. paper) 1. Foundations. 2.
Anchorage (Structural engineering) I. Shukla, Sanjay Kumar. II. Title.
TA775.D226 2013
624.1′5—dc23
2013010895
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TABLE OF CONTENTS
Preface .................................................................................................................. ix
The Authors ........................................................................................................ xi
Chapter 1. Earth Anchors: General .................................................................. 1
1.1. Introduction ............................................................................................... 1
1.2. Plate Anchors ............................................................................................. 3
1.3. Direct Embedment Anchors .................................................................... 4
1.4. Helical Anchors ......................................................................................... 4
1.5. Grouted Anchors ....................................................................................... 7
1.6. Anchor Piles and Drilled Shafts ............................................................ 10
1.7. Suction Caisson and Drag Anchors ...................................................... 12
1.8. Geo-Anchors ............................................................................................ 12
1.9. Coverage of the Text .............................................................................. 13
1.10. Summary of Main Points ....................................................................... 14
Self-Assessment Questions ................................................................................ 15
References ........................................................................................................... 17
Chapter 2. Horizontal Plate Anchors in Sand .............................................. 19
2.1. Introduction ............................................................................................. 19
2.2. Early Theories .......................................................................................... 21
2.2.1. Soil Cone Method ........................................................................ 21
2.2.2. Friction Cylinder Method ........................................................... 23
2.3. Balla’s Theory .......................................................................................... 25
2.4. Baker and Kondner’s Empirical Relationship ...................................... 27
2.5. Mariupol’skii’s Theory ............................................................................ 29
iii
iv Earth Anchors
2.6. Meyerhof and Adams’s Theory ............................................................. 31
2.7. Veesaert and Clemence’s Theory .......................................................... 42
2.8. Vesic’s Theory ......................................................................................... 45
2.9. Saeedy’s Theory ....................................................................................... 48
2.10. Discussion of Various Theories ............................................................. 52
2.11. Load-Displacement Relationship ........................................................... 57
2.12. Anchors Subjected to Repeated Loading .............................................. 62
2.13. Uplift Capacity of Shallow Group Anchors ......................................... 65
2.14. Spread Foundations under Uplift ......................................................... 69
2.15. Inclined Load Resistance of Horizontal Plate Anchors ...................... 71
2.16. Other Studies ........................................................................................... 74
2.17. Summary of Main Points ....................................................................... 75
Self-Assessment Questions ................................................................................ 77
References ........................................................................................................... 79
Chapter 3. Horizontal Plate Anchors in Clay .............................................. 81
3.1. Introduction ............................................................................................... 81
3.2. Vesic’s Theory ........................................................................................... 82
3.3. Meyerhof’s Theory ................................................................................... 84
3.4. Das’s Theory .............................................................................................. 85
3.5. Three-Dimensional Lower Bound Solution ........................................... 93
3.6. Factor of Safety ......................................................................................... 96
3.7. Uplift Capacity of Anchors in Layered Soil ........................................... 96
3.8. Other Studies ............................................................................................. 99
3.9. Summary of Main Points ....................................................................... 101
Self-Assessment Questions .............................................................................. 102
References ......................................................................................................... 103
Chapter 4. Vertical Plate Anchors ................................................................ 105
4.1. Introduction ............................................................................................. 105
4.2. Anchors in Sand ...................................................................................... 108
4.2.1. Ultimate Holding Capacity from Rankine’s Theory ................ 108
4.2.2. Analysis of Ovesen and Stromann ............................................. 112
4.2.3. Analysis of Meyerhof ................................................................... 122
4.2.4. Analysis of Biarez et al. ............................................................... 124
4.2.5. Analysis of Neely et al. ................................................................ 125
4.2.6. Nature of Passive Pressure Distribution in Front of
a Shallow Vertical Anchor .......................................................... 132
4.2.7. Deep Vertical Anchor .................................................................. 134
4.2.8. Load-Displacement Relationship ................................................ 138
Table of Contents v
4.2.9. Design Considerations ............................................................... 141
4.2.10. Effect of Anchor Inclination ..................................................... 149
4.3. Anchors in Clay (Undrained Cohesion, φ = 0) .................................. 150
4.3.1. Ultimate Holding Capacity ......................................................... 150
4.3.2. Step-by-Step Procedure for Estimation of Ultimate Load ...... 157
4.3.3. Limitations of the Existing Study ............................................... 160
4.4. Other Studies ........................................................................................... 160
4.5. Summary of Main Points ....................................................................... 161
Self-Assessment Questions .............................................................................. 162
References ......................................................................................................... 164
Chapter 5. Inclined Plate Anchors ............................................................... 167
5.1. Introduction ............................................................................................. 167
5.2. Inclined Plate Anchors in Sand ............................................................. 168
5.2.1. Inclined Anchors: Axisymmetric Case (Analysis of Harvey
and Burley) .................................................................................. 168
5.2.2. Meyerhof’s Procedure ................................................................. 172
5.2.3. Analysis of Hanna et al. .............................................................. 180
5.2.4. Other Empirical Relationships .................................................... 189
5.2.5. General Remarks .......................................................................... 194
5.3. Inclined Plate Anchors in Clay (φ = 0 Condition) ............................ 196
5.3.1. Ultimate Holding Capacity ......................................................... 196
5.4. Other Studies ............................................................................................ 204
5.5. Summary of Main Points ....................................................................... 205
Self-Assessment Questions .............................................................................. 205
References ......................................................................................................... 206
Chapter 6. Helical Anchors in Sand ............................................................ 209
6.1. Introduction ............................................................................................. 209
6.2. Single-Helix (Screw) Anchors ................................................................ 210
6.2.1. Ultimate Holding Capacity of Single-Helix (Screw)
Anchors ........................................................................................ 210
6.2.2. Holding Capacity of Group of Single-Helix (Screw)
Anchors ........................................................................................ 220
6.3. Multi-Helix Anchors ............................................................................... 221
6.3.1. Geometric Parameters and Failure Mode ................................. 221
6.3.2. Net Ultimate Uplift Capacity for Shallow Anchor
Condition ..................................................................................... 224
6.3.3. Net Ultimate Uplift Capacity for Deep Anchor Condition .... 234
6.4. Interference of Closely Spaced Anchors ............................................... 236
vi Earth Anchors
6.5. Other Studies ........................................................................................... 237
6.6. Summary of Main Points ....................................................................... 237
Self-Assessment Questions .............................................................................. 238
References ......................................................................................................... 239
Chapter 7. Helical Anchors in Clay ............................................................. 241
7.1. Introduction ............................................................................................. 241
7.2. Failure Mode ........................................................................................... 241
7.3. Net Ultimate Uplift Capacity ................................................................ 243
7.4. Numerical Modeling Solution ............................................................... 248
7.5. Use of In Situ Tests to Predict Uplift Performance ........................... 250
7.6. Other Studies ........................................................................................... 250
7.7. Summary of Main Points ....................................................................... 251
Self-Assessment Questions .............................................................................. 251
References ......................................................................................................... 252
Chapter 8. Anchor Piles ................................................................................. 253
8.1. Introduction ............................................................................................. 253
8.2. Piles in Sand ............................................................................................ 255
8.2.1. Bored Piles .................................................................................... 255
8.2.2. Driven Piles .................................................................................. 265
8.2.3. Uplift Capacity of Inclined Piles Subjected to Axial Pull ....... 268
8.2.4. Uplift Capacity of Rigid Vertical Piles under Oblique Pull .... 276
8.2.5. Uplift Capacity of Group Piles ................................................... 283
8.2.6. Factor of Safety ............................................................................ 284
8.3. Piles in Clay (φ = 0 Condition) ............................................................ 286
8.3.1. Vertical Piles Subjected to Axial Pull ........................................ 286
8.3.2. Load-Displacement Relationship for Vertical Piles
Subjected to Axial Uplift ............................................................ 290
8.3.3. Inclined Pile Subjected to Axial Pull ......................................... 292
8.3.4. Uplift Capacity of Vertical Pile Subjected to Inclined Pull .... 293
8.3.5. Uplift Capacity of Group Piles in Clay ..................................... 294
8.4. Summary of Main Points ..................................................................... 297
Self-Assessment Questions .............................................................................. 299
References ......................................................................................................... 300
Chapter 9. Suction Caisson and Drag Anchors ......................................... 301
9.1. Introduction ............................................................................................. 301
9.2. Suction Caisson Anchors ....................................................................... 301
9.3. Drag Anchors .......................................................................................... 306
Table of Contents vii
9.4. Summary of Main Points ....................................................................... 310
Self-Assessment Questions .............................................................................. 311
References ......................................................................................................... 312
Chapter 10. Geo-Anchors .............................................................................. 313
10.1. Introduction ........................................................................................... 313
10.2. Geotextile-Wrapped Anchors ............................................................... 313
10.3. Trench Anchors ..................................................................................... 318
10.4. Summary of Main Points ..................................................................... 324
Self-Assessment Questions .............................................................................. 324
References .......................................................................................................... 325
Index ................................................................................................................. 327

PREFACE
Anchors are primarily used in the construction of foundations for earth-sup-
ported and earth retaining structures. The fundamental reason for using earth
anchors in construction is to transmit the outwardly directed load to the soil
at a greater depth and(cid:1)or farther away from the structure. Although earth an-
chors have been used in practice for several hundred years, proper theoretical
developments for purposes of modern engineering design have taken place only
during the past 40 to 45 years or so. This book summarizes most theoretical and
experimental works related to the development of proper relationships for ul-
timate and allowable holding capacities of earth anchors.
The first edition of this book was published with a 1990 copyright by Elsevier
Science Publishers B.V., Amsterdam, The Netherlands, in the Developments in
Geotechnical Engineering Series (No. 50). It was reprinted with a 2007 copyright
by J. Ross Publishing in their Classics Series. Sanjay Kumar Shukla is the co-
author of this second edition. The book now has a total of ten chapters. In this
edition, the following major changes have been made:
• Horizontal plate anchors in sand are presented in Chapter 2 and hori-
zontal plate anchors in clay in Chapter 3.
• Helical anchors are now presented in two chapters: anchors in sand in
Chapter 6 and anchors in clay in Chapter 7. A discussion on single-helix
screw anchors in sand has been added to Chapter 6.
• Two new chapters have been added: suction and caisson anchors (Chap-
ter 9) and geo-anchors (Chapter 10).
• A summary section has been included for each chapter.
ix