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The Deep Mixing Method
The Deep Mixing Method
Masaki Kitazume & Masaaki Terashi
Kitazume
Terashi
The Deep Mixing Method (DMM), a deep in-situ soil stabilization technique
using cement and/or lime as a stabilizing agent, was developed in Japan
and in the Nordic countries independently in the 1970s. Numerous research
efforts have been made in these areas investigating properties of treated soil,
behavior of DMM improved ground under static and dynamic conditions,
design methods, and execution techniques.
Due to its wide applicability and high improvement effect, the method has
become increasingly popular in many countries in Europe, Asia and in the
USA. In the past three to four decades, traditional mechanical mixing has
been improved to meet changing needs. New types of the technology have also
been developed in the last 10 years; e.g. the high pressure injection mixing
method and the method that combines mechanical mixing and high pressure
injection mixing technologies. The design procedures for the DM methods
were standardized across several organizations in Japan and revised several
times. Information on these rapid developments will benefit those researchers
and practitioners who are involved in ground improvement throughout the
world.
The book presents the state of the art in Deep Mixing methods, and covers
recent technologies, research activities and know-how in machinery, design,
construction technology and quality control and assurance.
The Deep Mixing Method is a useful reference tool for engineers and
researchers involved in DMM technology everywhere, regardless of local soil
conditions and variety in applications.
The Deep Mixing Method
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1 Overview of ground improvement – evolution of deep mixing
and scope of the book 1
1 Introduction 1
2 Classification of ground improvement technologies 2
2.1 Replacement 3
2.2 Densification 3
2.3 Consolidation/dewatering 4
2.4 Grouting 5
2.5 Admixture stabilization 6
2.6 Thermal stabilization (heating and freezing) 7
2.7 Reinforcement 7
2.8 Combined uses of various techniques 7
2.9 Limitation of traditional ground improvement
techniques 8
3 Development of deep mixing in Japan – historical review 8
3.1 Development of the deep mixing method 8
3.2 Development of high pressure injection deep mixing
method 12
4 Diversified admixture stabilization techniques without
compaction 13
4.1 Classification of admixture stabilization techniques 13
4.2 In-situ mixing 15
4.2.1 Surface treatment 15
4.2.2 Shallow mixing 15
4.2.3 Deep mixing method 17
4.3 Ex-situ mixing 19
4.3.1 Premixing method 19
4.3.2 Lightweight Geo-material 20
4.3.3 Dewatered stabilized soil 22
4.3.4 Pneumatic flow mixing method 23

3.2.4 Influence of ignition loss 51
3.2.5 Influence of pH 51
3.2.6 Influence of water content 54
3.3 Mixing conditions 56
3.3.1 Influence of amount of binder 56
3.3.2 Influence of mixing time 56
3.3.3 Influence of time and duration of mixing and
holding process 56
3.4 Curing conditions 59
3.4.1 Influence of curing period 59
3.4.2 Influence of curing temperature 61
3.4.3 Influence of maturity 63
3.4.4 Influence of overburden pressure 67
4 Prediction of strength 68
References 69
3 Engineering properties of stabilized soils 73
1 Introduction 73
2 Physical properties 73
2.1 Change of water content 73
Table of contents vii
2.2 Change of unit weight 76
2.3 Change of consistency of soil-binder mixture before hardening 78
3 Mechanical properties (strength characteristics) 79
3.1 Stress–strain curve 79
3.2 Strain at failure 82
3.3 Modulus of elasticity (Yong’s modulus) 83
3.4 Residual strength 83
3.5 Poisson’s ratio 84
3.6 Angle of internal friction 86
3.7 Undrained shear strength 87

6.5 Difference in strength of field produced stabilized soil and
laboratory prepared stabilized soil 126
6.6 Size effect on unconfined compressive strength 128
6.7 Strength and calcium distributions at overlapped portion 131
6.7.1 Test conditions 131
6.7.2 Calcium distribution 132
6.7.3 Strength distribution 132
6.7.4 Effect of time interval 133
viii Table of contents
7 Summary 134
7.1 Physical properties 134
7.1.1 Change of water content and density 134
7.1.2 Change of consistency of soil-binder mixture before
hardening 135
7.2 Mechanical properties (strength characteristics) 135
7.2.1 Stress–strain behavior 135
7.2.2 Poisson’s ratio 135
7.2.3 Angle of internal friction 135
7.2.4 Undrained shear strength 135
7.2.5 Dynamic property 136
7.2.6 Creep and cyclic strengths 136
7.2.7 Tensile and bending strengths 136
7.2.8 Long term strength 136
7.3 Mechanical properties (consolidation characteristics) 137
7.3.1 Void ratio – consolidation pressure curve 137
7.3.2 Coefficient of consolidation and coefficient of volume
compressibility 137
7.3.3 Coefficient of permeability 137
7.4 Environmental properties 137
7.4.1 Elution of contaminant 137

4.2.1 Group column type – individual columns – for
settlement reduction 158
4.2.1.1 Introduction and ground condition 158
4.2.1.2 Ground improvement 158
4.2.2 Group column type – tangent block – for embankment
stability 159
4.2.2.1 Introduction and ground condition 159
4.2.2.2 Ground improvement 160
4.2.3 Grid type improvement for liquefaction prevention 162
4.2.3.1 Introduction and ground condition 162
4.2.3.2 Ground improvement 163
4.2.4 Block type improvement to increase bearing capacity of
a bridge foundation 165
4.2.4.1 Introduction and ground condition 165
4.2.4.2 Ground improvement 165
4.2.5 Block type improvement for liquefaction mitigation 167
4.2.5.1 Introduction and ground condition 167
4.2.5.2 Ground improvement 168
4.2.6 Grid type improvement for liquefaction prevention 168
4.2.6.1 Introduction and ground condition 168
4.2.6.2 Ground improvement 169
4.2.7 Block type improvement for the stability of a
revetment 171
4.2.7.1 Introduction and ground condition 171
4.2.7.2 Ground improvement 172
4.2.8 Jet grouting application to shield tunnel 174
4.2.8.1 Introduction and ground condition 174
4.2.8.2 Ground improvement 175
5 Performance of improved ground in the 2011 Tohoku earthquake 176
5.1 Introduction 176

3.1.1.2 Mixing tool 192
3.1.1.3 Binder plant 194
3.1.1.4 Control unit 195
3.1.2 Construction procedure 196
3.1.2.1 Preparation of site 196
3.1.2.2 Field trial test 196
3.1.2.3 Construction work 196
3.1.2.4 Quality control during production 199
3.1.3 Quality assurance 200
4 Wet method of deep mixing for on-land works 200
4.1 Ordinary cement deep mixing method 201
4.1.1 Equipment 201
4.1.1.1 System and specifications 201
4.1.1.2 Mixing tool 201
4.1.1.3 Binder plant 205
4.1.1.4 Control unit 205
4.1.2 Construction procedure 206
4.1.2.1 Preparation of site 206
4.1.2.2 Field trial test 206
4.1.2.3 Construction work 207
4.1.2.4 Quality control during production 209
4.1.2.5 Quality assurance 210
4.2 CDM-LODIC method 210
4.2.1 Equipment 210
4.2.1.1 System and specifications 210
4.2.1.2 Mixing tool 212
4.2.1.3 Binder plant 213
4.2.1.4 Control unit 213
Table of contents xi
4.2.2 Construction procedure 213

5.1.2.2 Positioning 228
5.1.2.3 Field trial test 228
5.1.2.4 Construction work 228
5.1.3 Quality control during production 230
5.1.3.1 Quality assurance 231
6 Additional issues to be considered in the mechanical mixing method 231
6.1 Soil improvement method for locally hard ground 231
6.2 Noise and vibration during operation 232
6.3 Lateral displacement and heave of ground by deep
mixing work 232
6.3.1 On-land work 232
6.3.2 In-water work 232
7 High pressure injection method 235
7.1 Single fluid technique (CCP method) 236
7.1.1 Equipment 236
7.1.2 Construction procedure 237
xii Table of contents
7.1.2.1 Preparation of site 237
7.1.2.2 Construction work 237
7.1.2.3 Quality control during production 238
7.1.2.4 Quality assurance 238
7.2 Double fluid technique (JSG method) 239
7.2.1 Equipment 239
7.2.2 Construction procedure 241
7.2.2.1 Preparation of site 241
7.2.2.2 Construction work 241
7.2.2.3 Quality control during production 243
7.2.2.4 Quality assurance 243
7.3 Double fluid technique (Superjet method) 244
7.3.1 Equipment 244

8.1.2.4 Quality control during production 259
8.1.2.5 Quality assurance 260
8.1.2.6 Effect of method 260
References 261
Table of contents xiii
6 Design of improved ground by the deep mixing method 263
1 Introduction 263
2 Engineering behavior of deep mixed ground 264
2.1 Various column installation patterns and their applications 264
2.2 Engineering behavior of block (grid and wall) produced by
overlap operation 266
2.2.1 Engineering behavior of improved ground leading to
external instability 266
2.2.2 Engineering behavior of improved ground leading to
internal instability 268
2.2.3 Change of failure mode 269
2.2.3.1 Influence of strength ratio q
ub
/q
us
on vertical
bearing capacity 270
2.2.3.2 Influence of load inclination 272
2.2.3.3 Influence of overlap joint on mode of failure 274
2.2.3.4 Influence of overlap joint on external stability 274
2.2.3.5 Influence of overlap joint on internal stability 277
2.2.3.6 Summary of failure modes for block type
improvement 278
2.3 Engineering behavior of a group of individual columns 280
2.3.1 Stability of a group of individual columns 280

area ratio and width of improved ground 307
4.3.9.2 Limitation of design procedure based on slip
circle analysis 308
5 Design procedure for block type and wall type improved grounds 309
5.1 Introduction 309
5.2 Basic concept 310
5.3 Design procedure 311
5.3.1 Design flow 311
5.3.2 Examination of the external stability of a superstructure 312
5.3.3 Trial values for the strength of stabilized soil and
geometric conditions of improved ground 314
5.3.4 Examination of the external stability of improved ground 314
5.3.4.1 Sliding and overturning failures 315
5.3.4.2 Bearing capacity 318
5.3.5 Examination of the internal stability of improved ground 320
5.3.5.1 Subgrade reaction at the front edge of
improved ground 321
5.3.5.2 Average shear stress along a vertical plane 322
5.3.5.3 Allowable strengths of stabilized soil 323
5.3.5.4 Extrusion failure 325
5.3.6 Slip circle analysis 327
5.3.7 Examination of immediate and long term settlements 328
5.3.8 Determination of strength and specifications of
stabilized soil 329
5.4 Sample calculation 329
5.5 Important issues on design procedure 330
6 Design procedure for block type and wall type improved grounds,
reliability design 330
6.1 Introduction 330
6.2 Basic concept 331

7.3.1 Design flow 351
7.3.2 Design seismic coefficient 352
7.3.3 Determination of width of grid 353
7.3.4 Assumption of specifications of improved ground 353
7.3.5 Examination of the external stability of improved ground 353
7.3.5.1 Sliding and overturning failures 353
7.3.5.2 Bearing capacity 358
7.3.6 Examination of the internal stability of improved
ground 360
7.3.6.1 Subgrade reaction at the front edge of
improved ground 360
7.3.6.2 Average shear stress along a horizontal
shear plane 360
7.3.6.3 Average shear stress along the horizontal plane
of the rear most grid wall 361
7.3.6.4 Average shear stress along a vertical shear
plane 362
7.3.7 Slip circle analysis 363
7.3.8 Important issues on design procedure 364
7.3.8.1 Effect of grid wall spacing on liquefaction
prevention 364
References 365
7 QC/QA for improved ground – Current practice and
future research needs 369
1 Introduction 369
2 Flow of a deep mixing project and QC/QA 369
3 QC/QA for stabilized soil – current practice 371
3.1 Relation of laboratory strength, field strength and
design strength 371
3.2 Flow of quality control and quality assurance 373

2.2.1 Soil 397
2.2.2 Binder 398
3 Making and curing of specimens 398
3.1 Mixing materials 398
3.2 Making specimen 399
3.3 Curing 400
3.4 Specimen removal 400
4 Report 405
5 Use of specimens 405
References 405
Subject index 407
Preface
The deep mixing method is a deep in-situ admixture stabilization technique using lime,
cement or lime-based and cement-based special binders. Compared to the other ground
improvement techniques deep mixing has advantages such as the large strength increase
within a month period, little adverse impact on environment and high applicability to
any kind of soil if binder type and amount are properly selected. The application
covers on-land and in-water constructions ranging from strengthening the foundation
ground of buildings, embankment supports, earth retaining structures, retrofit and
renovation of urban infrastructures, liquefaction hazards mitigation, man-made island
constructions and seepage control. Due to the versatility, the total volume of stabilized
soil by the mechanical deep mixing method from 1975 to 2010 reached 72.3 million m
3
for the wet method of deep mixing and 32.1 million m
3
for the dry method of deep
mixing in the Japanese market.
Improved ground by the method is a composite system comprising stiff stabi-
lized soil and un-stabilized soft soil, which necessitates geotechnical engineers to fully
understand the interaction of stabilized and unstabilized soil and the engineering char-

mixing rather than a user friendly manual. The book covers the factors affecting the
strength increase by deep mixing, the engineering characteristics of stabilized soil,
a variety of applications and associated column installation patterns, current design
procedures, execution systems and procedures, and QC/QA methods and procedures
based on the experience and research efforts accumulated in the past 40 years in Japan.
The authors wish the book is useful for practicing engineers to understand the
current state of the art and also useful for academia to find out the issues to be studied
in the future.
August 2012
Masaki Kitazume
Masaaki Terashi
List of technical terms and symbols
DEFINITION OF TECHNIC AL TERMS
additive chemical material to be added to stabilizing agent for
improving characteristics of stabilized soil
binder chemically reactive material that can be used for mixing with
in-situ soils to improve engineering characteristics of soils
such as lime, cement, lime-based and cement-based special
binders. Also referred to as stabilizer or stabilizing agent.
binder content ratio of weight of dry binder to the volume of soil to be
stabilized. (kg/m
3
)
binder factor ratio of weight of dry binder to the dry weight of soil to be
stabilized. (%)
binder slurry slurry-like mixture of binder and water
DM machine a machine to be used to construct stabilized soil column
external stability overall stability of the stabilized body
field strength strength of stabilized soil produced in-situ
fixed type a type of improvement in which a stabilized soil column

c
compression index of soft soil
C
g
subsoil condition factor
C
s
importance factor
c
u
undrained shear strength
c
ub
undrained shear strength of soil beneath improved ground (kN/m
2
)
c
uc
undrained shear strength of soft soil (kN/m
2
)
c
us
undrained shear strength of stabilized soil (kN/m
2
)
c
vs
coefficient of consolidation of stabilized soil
c

F
c
fine fraction content
f
m
coefficient of friction of mound
F
Ri
total shear force per unit length mobilized on bottom of improved ground
(kN/m)
F
Ru
total shear force per unit length mobilized on bottom of unstabilized soil
(kN/m)
f

ru
internal friction angle incorporating excess pore water pressure
F
s
safety factor
F
se
safety factor against extrusion failure
f
sh
design shear strength of stabilized soil (kN/m
2
)
Fs

G
sec
secant shear modulus
G
w
specific gravity of water
h depth from water surface (m)
H length of stabilized soil column (m)
H
c
thickness of ground (m)
List of technical terms and symbols xxi
H
cb
thickness of soil beneath improved ground (m)
H
e
height of embankment (m)
h
eq
damping ratio
H
f
height of periphery of improved ground mobilizing cohesion (m)
H
i
height of improved ground (m)
HK
bf
total seismic inertia force per unit length of backfill (kN/m)

water depth (m)
I
p
plasticity index
K coefficient of efficiency of soil removal
k coefficient of permeability
k mobilization factor of soil strength
K
A
coefficient of static active earth pressure
K
EA
coefficient of dynamic active earth pressure
K

EA
coefficient of dynamic active earth pressure incorporating pore water
pressure generation
K
EP
coefficient of dynamic passive force per unit length
K

EP
coefficient of dynamic passive earth pressure incorporating pore water
pressure generation
k
h
seismic coefficient
k

thickness of grid of improved ground (m)
L
u
unit length of improved ground (m)
M maturity
m ratio of generated heat for evaporating water in soil
m
vc
coefficient of volume compressibility of unstabilized soil (m
2
/kN)
m
vs
coefficient of volume compressibility of stabilized soil (m
2
/kN)
N number of rotation of helical screw
n stress concentration ratio (σ
s
/σ
c
)
xxii List of technical terms and symbols
N
c
bearing capacity factor of soil beneath improved ground
N
d
number of rotation of mixing shaft during penetration (N/min)
N

AHc
horizontal component of total static active force per unit length of soft
ground (kN/m)
P
AVc
vertical component of total static active force per unit length of soft ground
(kN/m)
P
DAH
horizontal component of total dynamic active earth and pore water forces
per unit length (kN/m)
P
DAHbf
total dynamic active force per unit length of backfill (kN/m)
P
DAHc
horizontal component of total dynamic active force per unit length of soft
ground (kN/m)
P
DAV
vertical component of total dynamic active earth and pore water forces per
unit length (kN/m)
P
DAVc
vertical component of total dynamic active force per unit length of soft
ground (kN/m)
P
DPH
horizontal component of total dynamic passive earth and pore water forces
per unit length (kN/m)

total surcharge force per unit length (kN/m)
p
y
consolidation yield pressure (the pseudo pre-consolidation pressure)
Q amount of binder (m
3
)
q volume of jet (m
3
/min.)
q
a
allowable bearing capacity (kN/m
2
)
q
ar
bearing capacity (kN/m
2
)
q
c
cone resistance,
q
c
volume of injected binder (m
3
/min.)
List of technical terms and symbols xxiii
q

design unconfined compressive strength of stabilized soil (kN/m
2
)
q
uf
unconfined compressive strength of in-situ stabilized soil (kN/m
2
)
q
ul
unconfined compressive strength of stabilized soil manufactured in
laboratory (kN/m
2
)
q
w
volume of high pressured water injected (m
3
/min.)
RQD rock quality designation index
R
u
bearing capacity of soil beneath stabilized soil column (kN/m)
r
u
excess pore water pressure ratio
S sectional area of helical screw (m
2
)
S settlement (m)

C)
t
m
mixing time of binder-slurry
t
r
rest time on the strength of stabilized soil
V amount of soil removed (m
3
)
V volume of slime (m
3
)
v withdrawal speed (min./m)
V
1
volume of slime due to column construction (m
3
)
V
2
volume of slime due to drilling (m
3
)
V
d
penetration speed of mixing shaft (m/min)
V
u
withdrawal speed of mixing shaft (m/min)

s
water content of stabilized soil (%)
W
s
weight per unit length of stabilized soil (kN/m)
xxiv List of technical terms and symbols
W
sp
weight per unit length of superstructure (kN/m)
W
u
weight per unit length of unstabilized soil (in case of wall type improvement)
(kN/m)
γ partial factor
α binder content
α characteristic of helical screw (m
3
)
α shape factor of foundation
α coefficient of effective width of stabilized soil column
α
c
modified maximum seismic acceleration (cm/s
2
)
β settlement reduction factor
β shape factor of foundation
β water binder ratio
β reliability coefficient of overlapping
δ friction angle of boundary of improved ground and unstabilized soil (

a
structural analysis factor
γ
d
reduction factor
γ
e
unit weight of embankment (kN/m
3
)
γ
i
structural factor
γ
SA
pulsating shear strain
γ
w
unit weight of water (kN/m
3
)
η amount of water evaporated due to heat by unit weight of CaO (0.478 g/g)
η ratio of required water for cement hydration
λ ratio of q
uf
/q
ul
µ Poisson’s ratio
µ
k

σ

c
effective confining pressure (kN/m
2
)
σ
c
vertical stress acting on soft ground between stabilized soil columns
(kN/m
2
)
σ
ca
allowable compressive strength of stabilized soil (kN/m
2
)
M total number of mixing blades