1.
Principles and Practices of Ground
Improvement

2.
Principles and Practices of
Ground Improvement
Jie Han

3.
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Library of Congress Cataloging-in-Publication Data:
Han, Jie, 1964-
Principles and practice of ground improvement / Jie Han.
pages cm
Includes bibliographical references and index.
ISBN 978-1-118-25991-7 (hardback); 978-1-118-41960-1 (ebk.); 978-1-118-42130-7 (ebk.)
1. Soil stabilization. 2. Foundations. I. Title.
TA749.H36 2014
624.1’51–dc23
2014018379
Cover images courtesy of Serge Varaksin and Jie Han
Cover design: Wiley
Printed in the United States of America
10 9 8 7 6 5 4 3 2 1

4.
CONTENTS
Preface xiii
CHAPTER 1 INTRODUCTION 1
1.1 Introduction 1
1.2 Problematic Geomaterials and Conditions 1
1.2.1 Problematic Geomaterials 1
1.2.2 Problematic Conditions 1
1.3 Geotechnical Problems and Failures 2
1.4 Ground Improvement Methods and Classification 2
1.4.1 Historical Developments 2
1.4.2 Classification 3
1.4.3 General Description, Function, and Application 5
1.5 Selection of Ground Improvement Method 5
1.5.1 Necessity of Ground Improvement 5
1.5.2 Factors for Selecting Ground Improvement Method 10
1.5.3 Selection Procedure 12
1.6 Design Considerations 12
1.7 Construction 13
1.8 Quality Control and Assurance 14
1.9 Recent Advances and Trends for Future Developments 14
1.9.1 Recent Advances 14
1.9.2 Trends for Future Developments 14
1.10 Organization of Book 14
Problems 14
References 15
CHAPTER 2 GEOTECHNICAL MATERIALS, TESTING, AND DESIGN 17
2.1 Introduction 17
2.2 Geomaterials and Properties 17
2.2.1 Classifications 17
2.2.2 Physical Properties 18
2.2.3 Mechanical Properties 19
v

5.
vi CONTENTS
2.2.4 Hydraulic Properties 25
2.2.5 Compaction of Geomaterial 26
2.3 Geosynthetics and Properties 29
2.3.1 Type of Geosynthetic 29
2.3.2 Function 30
2.3.3 Properties and Test Methods 33
2.4 In situ Testing 40
2.4.1 Standard Penetration Test 40
2.4.2 Cone Penetration Test 42
2.4.3 Vane Shear Test 45
2.4.4 Pressuremeter Test 46
2.4.5 Plate Load Test 47
2.5 Shallow Foundation Design 48
2.5.1 Bearing Capacity 48
2.5.2 Settlement 50
2.5.3 Consolidation 54
2.6 Slope Stability Analysis 55
2.6.1 Introduction 55
2.6.2 Methods for Slope Stability Analysis 55
2.7 Earth Retaining Wall Analysis 61
2.7.1 Type of Wall 61
2.7.2 Lateral Earth Pressure Coefficient 61
2.7.3 Rankine’s Theory 61
2.7.4 Coulomb’s Theory 63
2.8 Liquefaction Analysis 64
2.8.1 Liquefaction Potential 64
2.8.2 Earthquake-Induced Settlement 66
Problems 67
References 70
CHAPTER 3 SHALLOW AND DEEP COMPACTION 73
3.1 Introduction 73
3.2 Densification Principles 73
3.3 Conventional Compaction 73
3.3.1 Introduction 73
3.3.2 Principles 74
3.3.3 Design Considerations 77
3.3.4 Design Parameters and Procedure 80
3.3.5 Design Example 80
3.3.6 Construction 81
3.3.7 Quality Control and Assurance 82
3.4 Intelligent Compaction 82
3.4.1 Introduction 82
3.4.2 Principles 83
3.4.3 Design Considerations 86
3.4.4 Construction 88
3.4.5 Quality Control and Assurance 88
3.5 Deep Dynamic Compaction 89
3.5.1 Introduction 89
3.5.2 Principles 90
3.5.3 Design Considerations 91
3.5.4 Design Parameters and Procedure 97
3.5.5 Design Example 98

6.
CONTENTS vii
3.5.6 Construction 99
3.5.7 Quality Control and Assurance 99
3.6 Rapid Impact Compaction 100
3.6.1 Introduction 100
3.6.2 Principles 101
3.6.3 Design Considerations 101
3.6.4 Design Parameters and Procedure 103
3.6.5 Design Example 103
3.6.6 Construction 104
3.6.7 Quality Control and Assurance 104
3.7 Vibro-compaction 104
3.7.1 Introduction 104
3.7.2 Principles 106
3.7.3 Design Considerations 109
3.7.4 Design Parameters and Procedure 110
3.7.5 Design Example 111
3.7.6 Construction 112
3.7.7 Quality Control and Assurance 113
Problems 113
References 115
CHAPTER 4 OVEREXCAVATION AND REPLACEMENT 117
4.1 Introduction 117
4.1.1 Basic Concept 117
4.1.2 Suitability 117
4.1.3 Applications 117
4.1.4 Advantages and Limitations 117
4.2 Principles 118
4.2.1 Stress Distribution 118
4.2.2 Failure Modes 119
4.3 Design Considerations 119
4.3.1 General Shear Failure within Replaced Zone 120
4.3.2 Punching Failure through the Replaced Zone 120
4.3.3 Failure of Distributed Foundation 121
4.3.4 Punching Failure of Replaced Zone into In Situ Soil 121
4.3.5 Minimum Bearing Capacity and Factor of Safety 122
4.3.6 Settlement of a Footing on Layered Soils of Infinite Width 122
4.3.7 Settlement of a Footing on a Replaced Zone with Limited Area 122
4.4 Design Parameters and Procedure 124
4.4.1 Design Parameters 124
4.4.2 Design Procedure 124
4.5 Design Example 125
4.6 Construction 130
4.6.1 Selection of Fill 130
4.6.2 Excavation 131
4.6.3 Placement and Compaction 131
4.7 Quality Control and Assurance 131
4.7.1 Locations and Dimensions 131
4.7.2 Compacted Fill 131
4.7.3 Performance Evaluation 131
Problems 131
References 132

7.
viii CONTENTS
CHAPTER 5 DEEP REPLACEMENT 133
5.1 Introduction 133
5.1.1 Basic Concepts 133
5.1.2 Suitability 135
5.1.3 Applications 135
5.1.4 Advantages and Limitations 135
5.2 Principles 136
5.2.1 Functions 136
5.2.2 Densification 136
5.2.3 Load Transfer Mechanisms 137
5.2.4 Failure Modes 140
5.3 Design Considerations 141
5.3.1 General Rules 141
5.3.2 Densification Effect 142
5.3.3 Bearing Capacity 143
5.3.4 Settlement 145
5.3.5 Consolidation 148
5.3.6 Stability 151
5.3.7 Liquefaction 152
5.3.8 Design of Geosynthetic-encased Granular Columns 153
5.4 Design Parameters and Procedure 156
5.4.1 Granular Columns 156
5.4.2 Concrete Columns 157
5.4.3 Geosynthetic-encased Granular Column 157
5.5 Design Examples 158
5.6 Construction 163
5.6.1 Sand Compaction Columns 163
5.6.2 Stone Columns 163
5.6.3 Rammed Aggregate Columns 164
5.6.4 Vibro-Concrete Columns 164
5.6.5 Controlled Modulus (Stiffness) Columns 165
5.6.6 Geosynthetic-encased Granular Columns 165
5.7 Quality Control and Assurance 165
5.7.1 Locations and Dimensions 165
5.7.2 Fill Material 165
5.7.3 Installation Parameters 166
5.7.4 Performance Evaluation 167
Problems 168
References 170
CHAPTER 6 DRAINAGE AND DEWATERING 173
6.1 Introduction 173
6.2 Principles of Water Flow in Geomaterial 174
6.2.1 Bernoulli’s Equation 174
6.2.2 Flow Net 175
6.2.3 Pore Water Pressure and Uplift Force 176
6.2.4 Stresses Due to Seepage 176
6.3 Filtration 177
6.3.1 Introduction 177
6.3.2 Principles 178

8.
CONTENTS ix
6.3.3 Design Considerations 180
6.3.4 Design Parameters and Procedure 184
6.3.5 Design Example 185
6.3.6 Construction 185
6.3.7 Quality Control and Assurance 185
6.4 Drainage 185
6.4.1 Introduction 185
6.4.2 Principles 187
6.4.3 Design Considerations 188
6.4.4 Design Parameters and Procedure 193
6.4.5 Design Examples 194
6.4.6 Construction 195
6.4.7 Quality Control and Assurance 195
6.5 Dewatering 196
6.5.1 Introduction 196
6.5.2 Principles 199
6.5.3 Design Considerations 200
6.5.4 Design Parameters and Procedure 202
6.5.5 Design Example 205
6.5.6 Construction 206
6.5.7 Quality Control and Assurance 206
Problems 206
References 209
CHAPTER 7 PRELOADING 211
7.1 Introduction 211
7.1.1 Basic Concept 211
7.1.2 Suitability 211
7.1.3 Applications 212
7.1.4 Advantages and Limitations 212
7.2 Principles 212
7.2.1 Precompression 212
7.2.2 Stress and Ground Movement 213
7.2.3 Consolidation Theory 214
7.2.4 Vacuum and Fill Combined Preloading 217
7.2.5 Surcharge Preloading 217
7.3 Design Considerations 218
7.3.1 Vertical Drains 218
7.3.2 Preloading 220
7.3.3 Surcharge Effect 223
7.4 Design Parameters and Procedures 226
7.4.1 Design Parameters 226
7.4.2 Design Procedure 226
7.5 Design Example 227
7.6 Construction 235
7.6.1 Vertical Drains 235
7.6.2 Drainage Layer 235
7.6.3 Fill Preloading 236
7.6.4 Vacuum Preloading 237
7.7 Quality Control and Assurance 237
7.7.1 Materials 238

9.
x CONTENTS
7.7.2 Construction Details 238
7.7.3 Field Monitoring 238
7.7.4 Performance Evaluation 240
Problems 240
References 242
CHAPTER 8 DEEP MIXING AND GROUTING 245
8.1 Introduction 245
8.2 Deep Mixing 245
8.2.1 Introduction 245
8.2.2 Principles 248
8.2.3 Design Considerations 259
8.2.4 Design Parameters and Procedure 268
8.2.5 Design Example 268
8.2.6 Construction 270
8.2.7 Quality Control and Assurance 272
8.3 Grouting 273
8.3.1 Introduction 273
8.3.2 Principles 275
8.3.3 Design Considerations 283
8.3.4 Design Parameters and Procedure 289
8.3.5 Design Example 289
8.3.6 Construction 290
8.3.7 Quality Control and Assurance 291
Problems 291
References 293
CHAPTER 9 IN SITU GROUND REINFORCEMENT 297
9.1 Introduction 297
9.2 Ground Anchors 297
9.2.1 Introduction 297
9.2.2 Principles 300
9.2.3 Design Considerations 303
9.2.4 Design Parameters and Procedure 311
9.2.5 Design Example 311
9.2.6 Construction 313
9.2.7 Quality Control and Assurance 313
9.3 Soil Nailing 314
9.3.1 Introduction 314
9.3.2 Principle 315
9.3.3 Design Considerations 318
9.3.4 Design Parameters and Procedure 327
9.3.5 Design Example 328
9.3.6 Construction 329
9.3.7 Quality Control and Assurance 329
Problems 330
References 332
CHAPTER 10 FILL REINFORCEMENT 333
10.1 Introduction 333
10.2 Geosynthetic-Reinforced Slopes 333

10.
CONTENTS xi
10.2.1 Introduction 333
10.2.2 Principles 334
10.2.3 Design and Analysis 336
10.2.4 Design Parameters and Procedure 341
10.2.5 Construction 344
10.2.6 Quality Control and Assurance 345
10.3 Geosynthetic-Reinforced Embankments 345
10.3.1 Introduction 345
10.3.2 Principles 345
10.3.3 Design Considerations 346
10.3.4 Design Parameters and Procedure 351
10.3.5 Construction 352
10.3.6 Quality Control and Assurance 353
10.4 Geosynthetic-Reinforced Column-Supported Embankments 353
10.4.1 Introduction 353
10.4.2 Principles 354
10.4.3 Design Considerations 359
10.4.4 Design Parameters and Procedure 362
10.4.5 Construction 363
10.4.6 Quality Control and Assurance 363
10.5 Mechanically Stabilized Earth Walls 364
10.5.1 Introduction 364
10.5.2 Principles 364
10.5.3 Design Considerations 367
10.5.4 Design Parameters and Procedure 370
10.5.5 Construction 374
10.5.6 Quality Control and Assurance 374
10.6 Geosynthetic-Reinforced Foundations 375
10.6.1 Introduction 375
10.6.2 Principles 375
10.6.3 Design Considerations 377
10.6.4 Design Parameters and Procedure 380
10.6.5 Construction 382
10.6.6 Quality Control and Assurance 382
10.7 Geosynthetic-Reinforced Roads 382
10.7.1 Introduction 382
10.7.2 Principles 383
10.7.3 Design Considerations for Unpaved Roads 387
10.7.4 Design Parameters and Procedure for Unpaved Roads 389
10.7.5 Design Considerations for Paved Roads 390
10.7.6 Design Parameters and Procedure for Paved Roads 392
10.7.7 Design Examples 393
10.7.8 Construction 396
10.7.9 Quality Control and Assurance 396
Problems 396
References 399
INDEX 403

11.
PREFACE
Ground improvement is popular in many countries to solve
difficult geotechnical problems, especially when construc-
tion necessarily occurs in problematic soils and under
difficult geotechnical conditions. Many recent developments
in equipment, materials, and design methods have made
ground improvement technologies more effective, efficient,
and economic. However, the state of practice for most ground
improvement technologies is that the practice is ahead of
theory. Some contractors have developed their proprietary
technologies, design methods, and construction techniques
for their competitive advantages. Most of the existing books
on ground improvement are focused on the concept, applica-
tion, and case study. However, few books have been devoted
to the principles and design methods of ground improvement.
This book covers both theoretical and practical aspects in the
design and construction of a variety of ground improvement
technologies commonly used in practice. This book includes
detailed design procedures for most of the ground improve-
ment methods, which enable their easy implementation in
practice. The design examples and homework assignments
in this book will help readers better understand the principles
of each ground improvement technology and how to apply
the principles to solve real problems. This book can be
used as a textbook for upper-level undergraduate students
and graduate students and a reference book for researchers
and practicing engineers. It can also be used a guide for
contractors and installers to implement ground improvement
technologies in field.
Writing this book was part of my big dream when I left
China in 1993 to pursue my Ph.D. degree at the Geor-
gia Institute of Technology. At that time, I set three goals:
(1) to obtain a Ph.D. degree in the United States, (2) to
publish technical papers on internationally well-recognized
journals, and (3) to write a book on ground improvement in
English. The first two goals were fulfilled in the late 1990s.
The last goal has taken much longer than I expected.
I started to become interested in ground improvement in
1985 when I took the class of ground improvement at Tongji
University in China, taught by Prof. Shulin Ye, as part of
my bachelor’s degree. I became a master’s student in 1986,
studying under Prof. Ye on stone columns. After I received
my master’s degree in 1989, I became a faculty member
at Tongji University, continuing my research in ground
improvement, including stone columns, deep mixed
columns, grouting, dynamic compaction, and micropiles. I
was fortunate to get involved in writing the first Shanghai
ground improvement design code. I also coauthored a
textbook on ground improvement in Chinese with Prof.
Shulin Ye and Prof. Guanbao Ye right before I left China.
The selection of the Georgia Institute of Technology for my
Ph.D. study was also related to ground improvement because
I had read the research report Design and Construction of
Stone Columns, written by then Prof. Richard D. Barksdale
for the U.S. Federal Highway Administration. I arrived at
Georgia Tech at a great time. I was exposed to many new
and innovative subjects and ideas and learned a great deal
about the scientific aspects of geotechnical engineering. My
Ph.D. research on fiber-reinforced polymeric piles, under
the supervision of Prof. J. David Frost, provided me the
great opportunity of learning composite mechanics and
geosynthetics. This led me to my first job in the United
States at one of the leading geosynthetics manufacturers,
the Tensar Corporation. I started with a design engineer and
was promoted to a senior engineer and then manager of
technology development. I was exposed to many practical
problems related to geosynthetic-reinforced earth structures.
After several attempts at obtaining faculty positions, I joined
Widener University in 2001 and taught the first ground
improvement class there. Since transfering to the University
of Kansas, I have worked closely with my colleague,
Prof. Robert L. Parsons, and been involved in many research
projects, which were sponsored by the federal agencies,
xiii

12.
xiv PREFACE
Kansas Department of Transportation, and the geosynthetics
and ground improvement industries.
Many people have made positive impacts on my career
in geotechnical engineering, especially in ground improve-
ment. In addition to my master’s advisor, Prof. Ye, and my
Ph.D. advisor, Prof. Frost, I have been fortunate to have op-
portunities to work with internationally recognized scholars
Dr. J.P. Giroud, Prof. Dov Leshchinsky, Dr. James Collin,
Prof. Mo Gabr, Prof. Hoe Ling and others. As part of the
major U.S. Strategic Highway Research Program (SHRP)
II R02 project team led by Prof. Vernon R. Schaefer and
Mr. Ryan Berg, I had the opportunity to work with the top
researchers and experts in ground improvement, including
Prof. James Mitchell. I have also been fortunate enough to
work with many talent and hard-working students and visit-
ing scholars through the years.
I appreciate the review comments and suggestions from
the experts in this field, including Dr. Dimiter Alexiew, Prof.
Jinchun Chai, Dr. Xin Chen, Prof. Jian Chu, Prof. Masaki
Kitazume, Prof. Dov Leshchinsky, Prof. Paul Mayne, Prof.
Shuilong Shen, Prof. Burak Tanyu, Dr. Mark Wayne, Prof.
Ming Xiao, and Mr. Kenny Yee. During the preparation of
this book, I received great help from my current and former
students, especially Yan Jiang, Shaymaa Kadhim, Deep Kha-
tri, Xiaohui Sun, Fei Wang, and Zhen Zhang. I am also thank-
ful for Mr. Serge Varaksin to provide the beautiful photo
for the book cover. Many organizations and individuals have
granted me permissions to republish their figures and tables
in this book and their generous support is greatly appreciated.
Finally, I would like to acknowledge the editors at John
Wiley & Sons, Inc. for their patience and great support. My
heartfelt thanks go to my dear wife, Jing Ye, and two sons,
Terry and Shawn, for their understanding and support for me
to complete this book.
Please go to www.wiley.com/go/GroundImprovement for
instructor materials.

13.
CHAPTER 1
Introduction
1.1 INTRODUCTION
With civilization and urbanization, there have been increased
demands for the use of land for better living and transporta-
tion. More and more houses, commercial buildings, high-rise
office buildings, highways, railways, tunnels, levees, and
earth dams have been constructed and will be continuously
built in the future. As suitable constrsuction sites with fa-
vorable geotechnical conditions become less available, the
need to utilize unsuitable or less suitable sites for construc-
tion increases. Engineers have faced increased geotechni-
cal problems and challenges, such as bearing failure, large
total and differential settlements, instability, liquefaction,
erosion, and water seepage. The options to deal with prob-
lematic geomaterials and geotechnical conditions include:
(1) avoiding the site, (2) designing superstructures accord-
ingly, (3) removing and replacing problematic geomaterials
with better and non-problematic geomaterials and (4) im-
proving geomaterial properties and geotechnical conditions
(Hausmann, 1990). It becomes increasingly necessary to im-
prove geomaterials and geotechnical conditions for many
projects.
Ground improvement has become an important part of
geotechnical practice. Different terminologies have been
used in the literature for ground improvement, such as
soil improvement, soil stabilization, ground treatment, and
ground modification. The term “ground improvement” has
been most commonly used in the literature and practice and
therefore adopted for this book.
1.2 PROBLEMATIC GEOMATERIALS
AND CONDITIONS
1.2.1 Problematic Geomaterials
Geomaterials include all the materials used for geotechnical
applications,whichconsistofnaturalgeomaterials,processed
or manufactured geomaterials, and improved geomaterials.
Natural geomaterials are mainly soil and rock. O’Neill and
Reese (1999) proposed a terminology of intermediate geo-
material, which has properties and behavior between soil and
rock. Cohesive intermediate geomaterial has an unconfined
compressive strength from 0.5 to 5.0 MPa, while a cohesion-
less intermediate geomaterial has the number of blow counts
of a standard penetration test (SPT) between 50 and 100.
Most rocks and intermediate geomaterials are strong and stiff
and therefore suitable for geotechnical applications. How-
ever, natural soils, especially soft clay and silt, loose sand,
expansive soil, collapsible soil, and frozen soil can be prob-
lematic to geotechnical applications.
Processed or manufactured geomaterials are produced
from other materials. For example, crushed stone aggregates
are produced from rock. Recycled asphalt pavement (RAP)
aggregates are produced from aged asphalt pavements.
Lightweight aggregates are produced by heating raw shale,
clay or slate in a rotary kiln at high temperatures, causing the
material to expand, and then cooling, crushing, and screen-
ing it for different applications. Processed or manufactured
geomaterials are mainly used for fill materials, which have
a wide variety, ranging from granular fill, lightweight fill,
uncontrolled fill, recycled material, fly ash, solid waste,
and bio-based byproducts to dredged material. Due to the
large variations of fill materials, some of them can be used
to improve soil properties (e.g., granular fill and fly ash),
but others can be problematic to geotechnical applications
(e.g., uncontrolled fill and sludge). Uncontrolled fill or
uncompacted fill is mostly loose and underconsolidated;
therefore, it settles under its own weight.
Improved geomaterials are the geomaterials treated hy-
draulically, mechanically, chemically, and biologically. For
example, fibers can be mechanically mixed with sand or clay
to form fiber-reinforced soil. Lime or cement can be added
into soil to form lime or cement-stabilized soil. Denitrifying
bacteria can be introduced into soil to generate tiny, inert ni-
trogen gas bubbles to reduce the degree of saturation of sand
(He et al., 2013). As a result, the liquefaction potential of
the sand is minimized. Improved geomaterials are often the
end products of ground improvement; therefore, they are not
problematic to geotechnical applications.
Table 1.1 lists problematic geomaterials and their potential
problems. Some natural geomaterials and fill are the targets
of ground improvement. When natural geomaterials are dis-
cussed in this book, soil and rock are often referred because
these terms are commonly used in practice.
1.2.2 Problematic Conditions
In addition to problematic geomaterials, geotechnical prob-
lems may occur due to problematic conditions induced nat-
urally and/or by human activities. Natural conditions in-
clude geologic, hydraulic, and climatic conditions, such
1

14.
2 1 INTRODUCTION
Table 1.1 Problematic Geomaterials and Potential Problems
Type of Geomaterial Name Potential Problems
Natural Soft clay Low strength, high compressibility, large creep deformation, low permeability
Silt Low strength, high compressibility, high liquefaction potential, low
permeability, high erodibility
Organic soil High compressibility, large creep deformation
Loose sand Low strength, high compressibility, high liquefaction potential, high
permeability, high erodibility
Expansive soil Large volume change
Loess Large volume change, high collapsible potential
Fill Uncontrolled fill Low strength, high compressibility, nonuniformity, high collapsible potential
Dredged material High water content, low strength, high compressibility
Reclaimed fill High water content, low strength, high compressibility
Recycled material Nonuniformity, high variability of properties
Solid waste Low strength, high compressibility, nonuniformity, and high degradation
potential
Bio-based by-product Low strength, high compressibility, and high degradation potential
as earthquakes, cavities and sinkholes, floods, wind, and
freeze−thaw cycles. Geotechnical conditions are part of ge-
ologic conditions, which exist close to the ground surface
and are more related to construction and human activities.
Examples of problematic geotechnical conditions are exis-
tence of problematic geomaterials, a high groundwater table,
inclined bedrock, and steep natural slopes. Human activities,
mainly the construction of superstructures, substructures, and
earth structures, can change geotechnical conditions, which
may cause problems for projects, for example, excavation,
tunneling, pile driving, rapid drawdown of surface water,
elevation of surface water by levees and dams, and ground-
water withdrawal. Human activities can also change other
conditions, such as the application of static, dynamic, and
impact loads.
1.3 GEOTECHNICAL PROBLEMS AND FAILURES
Common geotechnical problems include bearing failure,
large total and differential settlements, hydrocompression,
ground heave, instability, liquefaction, erosion, and water
seepage. The theoretical bases and reasons for these
geotechnical problems are provided in Table 1.2.
Failures can happen if geotechnical problems are not prop-
erly addressed and become excessive, which typically results
in significant financial loss, sometimes even cause loss of life.
1.4 GROUND IMPROVEMENT METHODS
AND CLASSIFICATION
1.4.1 Historical Developments
Ground improvement methods have been used since ancient
times. For example, about 6000 years ago (in the Neolithic
Age), the Banpo people in China used rammed columns to
support wooden posts in the ground (Chen et al., 1995).
Soil compaction methods using rammers have also been em-
ployed since the Neolithic Age. Different types of rammers
were used, from stone rammers (in the Neolithic Age) to iron
rammers (about 1000 years ago). One type of rammer was
operated by 8−12 people, each pulling a rope connected to
the rammer to raise it and then letting it fall freely to pound
the ground (Chen et al., 1995). About 3500 years ago, reeds
in the form of bound cables (approximately 100 mm in di-
ameter) were used in Iraq as horizontal drains for dissipation
of pore water pressure in soil mass in high earth structures
(Mittal, 2012). About 2000 years ago, The Romans used lime
for roadway construction. More than 1000 years ago in the
Han dynasty, Chinese people built earth retaining walls us-
ing local sand and weeds for border security and paths to the
Western world. About 500 years ago (in the Ming dynasty of
China), lime was mixed with clayey soil in proportion (typ-
ically 3:7 or 4:6 in volume) to form compacted lime−soil
foundations for load support (Chen et al., 1995).
Modern ground improvement methods were developed
since the 1920s. For example, the use of vertical sand drains
to accelerate consolidation of soft soil was first proposed in
1925 and then patented in 1926 by Daniel D. Moran in the
United States. Cotton fabric was used as reinforcement by
South Carolina Highway Department in the United States for
roadway construction in 1926. The vibro-flotation method
was developed in Germany to densify loose cohesionless soil
in 1937. The first type of prefabricated vertical drains was
developed by Walter Kjellman in Sweden in 1947. Fernando
Lizzi developed and patented the root pile method to under-
pin existing foundations in Italy in 1952. In the 1960s, there

15.
GROUND IMPROVEMENT METHODS AND CLASSIFICATION 3
Table 1.2 Geotechnical Problems and Possible Causes
Problem Theoretical Basis Possible Causes
Bearing failure Applied pressure is higher than ultimate
bearing capacity of soil
High applied pressure
Inclined load
Small loading area
Low-strength soil
Large total and differential
settlements
Hooke’s law and particle re-arrangement High applied pressure
Large loading area
Highly compressible soil
Nonuniform soil
Large creep deformation
Hydrocompression High applied pressure is higher than
threshold collapse stress
High applied pressure
Collapsible soil
Water
Ground heave Swelling pressure is higher than applied
pressure
Water
Expansive soil
Frozen soil
Low temperature
Instability (sliding,
overturning, and slope
failure)
Shear stress is higher than shear strength;
driving force is higher than resisting
force; driving moment is higher than
resisting moment
High earth structure
Steep slope
High water pressure
Soft foundation soil
High surcharge
High loading rate
Liquefaction Effective stress becomes zero due to
increase of excess pore water pressure
Earthquake
Loose silt and sand
High groundwater table
Erosion Shear stress induced by water is higher
than maximum allowable shear
strength of soil
Running water
High speed of water flow
Highly erodible soil (silt and sand)
Seepage Dacy’s law High water head
Permeable soil
were several developments of ground improvement methods,
including the steel reinforcement for retaining walls by Henri