The Deep Mixing Method – Masaki Kitazume, Masaaki Terashi (KENM0005)

The Deep Mixing Method – Masaki Kitazume, Masaaki Terashi

CONTENTS:

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

5 Scope of the text 24

2 Factors affecting strength increase

1 Introduction 29

2 Influence of various factors on strength of lime stabilized soil 30

2.1 Mechanism of lime stabilization 30

2.2 Characteristics of lime as a binder 31

2.2.1 Influence of quality of quicklime 32

2.3 Characteristics and conditions of soil 34

2.3.1 Influence of soil type 34

2.3.2 Influence of grain size distribution 35

2.3.3 Influence of humic acid 36

2.3.4 Influence of potential Hydrogen (pH) 36

2.3.5 Influence of water content 37

2.4 Mixing conditions 38

2.4.1 Influence of amount of binder 38

2.4.2 Influence of mixing time 39

2.5 Curing conditions 39

2.5.1 Influence of curing period 39

3 Influence of various factors on strength of cement stabilized soil 40

3.1 Mechanism of cement stabilization 40

3.1.1 Characteristics of binder 41

3.1.2 Influence of chemical composition of binder 42

3.1.3 Influence of type of binder 44

3.1.4 Influence of type of water 45

3.2 Characteristics and conditions of soil 47

3.2.1 Influence of soil type 47

3.2.2 Influence of grain size distribution 49

3.2.3 Influence of humic acid 50

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

3 Engineering properties of stabilized soils

1 Introduction 73

2 Physical properties 73

2.1 Change of water content 73

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

3.8 Dynamic property 87

3.9 Creep strength 88

3.10 Cyclic strength 90

3.11 Tensile and bending strengths 94

3.12 Long term strength 96

3.12.1 Strength increase 97

3.12.2 Strength decrease 100

4 Mechanical properties (consolidation characteristics) 105

4.1 Void ratio – consolidation pressure curve 105

4.2 Consolidation yield pressure 106

4.3 Coefficient of consolidation and coefficient of volume compressibility 107

4.4 Coefficient of permeability 110

4.4.1 Permeability of stabilized clay 110

4.4.2 Influence of grain size distribution on the coefficient of permeability of stabilized soil 112

5 Environmental properties 113

5.1 Elution of contaminant 113

5.2 Elution of Hexavalent chromium (chromium VI) from stabilized soil 115

5.3 Resolution of alkali from stabilized soil 119

6 Engineering properties of cement stabilized soil manufactured in situ 122

6.1 Mixing degree of in-situ stabilized soils 122

6.2 Water content distribution 122

6.3 Unit weight distribution 123

6.4 Variability of field strength 124

6.5 Difference in strength of field produced stabilized soil and laboratory prepared stabilized soil

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

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

7.4.2 Resolution of alkali from a stabilized soil 138

7.5 Engineering properties of cement stabilized soil manufactured in situ 138

7.5.1 Water content and unit weight by stabilization 138

7.5.2 Variability of field strength 138

7.5.3 Difference in the strength of field produced stabilized soil and laboratory prepared  stabilized soil 138

7.5.4 Size effect on unconfined compressive strength 138

7.5.5 Strength distributions at overlapped portion 138

4 Applications

1 Introduction 143

2 Patterns of applications 143

2.1 Size and geometry of the stabilized soil element 143

2.2 Column installation patterns by the mechanical deep mixing method 144

2.2.1 Group column type improvement 145

2.2.2 Wall type improvement 147

2.2.3 Grid type improvement 147

2.2.4 Block type improvement 148

2.3 Column installation pattern by high pressure injection 150

3 Improvement purposes and applications 150

3.1 Mechanical deep mixing method 150

3.2 High pressure injection 153

4 Applications in Japan 154

4.1 Statistics of applications 154

4.1.1 Mechanical deep mixing 154

4.1.2 Statistics of high pressure injection 157

4.2 Selected case histories 157

4.2.1 Group column type – individual columns – for settlement reduction 158

4.2.2 Group column type – tangent block – for embankment stability 159

4.2.3 Grid type improvement for liquefaction prevention 162

4.2.4 Block type improvement to increase bearing capacity of a bridge foundation 165

4.2.5 Block type improvement for liquefaction mitigation 167

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

4.2.8 Jet grouting application to shield tunnel 174

5 Performance of improved ground in the 2011 Tohoku earthquake 176

5.1 Introduction 176

5.2 Improved ground by the wet method of deep mixing 176

5.2.1 Outline of survey 176

5.2.2 Performance of improved ground 177

5.2.3 River embankment in Ibaraki Prefecture 177

5.2.4 Road embankment in Chiba Prefecture 177

5.3 Improved ground by the dry method of deep mixing 180

5.3.1 Outline of survey 180

5.3.2 Performance of improved ground 181

5.4 Improved ground by Grouting method 182

5.4.1 Outline of survey 182

5.4.2 Performance of improved ground 183

5.5 Summary 184

5 Execution – equipment, procedures and control

1 Introduction 187

1.1 Deep mixing methods by mechanical mixing process 187

1.2 Deep mixing methods by high pressure injection mixing process 188

2 Classification of deep mixing techniques in Japan 189

3 Dry method of deep mixing for on-land works 189

3.1 Dry jet mixing method 189

3.1.1 Equipment 189

3.1.2 Construction procedure 196

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

4.1.2 Construction procedure 206

4.2 CDM-LODIC method 210

4.2.1 Equipment 210

4.2.2 Construction procedure 213

4.2.3 Quality control during production 215

4.2.4 Quality assurance 215

4.2.5 Effect of method – horizontal displacement during execution 215

4.3 CDM-Lemni 2/3 method 216

4.3.1 Equipment 216

4.3.2 Construction procedure 220

4.3.3 Quality control during execution 220

5 Wet method of deep mixing for in-water works 222

5.1 Cement deep mixing method 222

5.1.1 Equipment 222

5.1.2 Construction procedure 227

5.1.3 Quality control during production 230

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

7.2 Double fluid technique (JSG method) 239

7.2.1 Equipment 239

7.2.2 Construction procedure 241

7.3 Double fluid technique (Superjet method) 244

7.3.1 Equipment 244

7.3.2 Construction procedure 244

7.4 Triple fluid technique (CJG method) 247

7.4.1 Equipment 247

7.4.2 Construction procedure 248

7.5 Triple fluid technique (X-jet method) 251

7.5.1 Equipment 251

7.5.2 Construction procedure 252

8 Combined technique 254

8.1 JACSMAN method 255

8.1.1 Equipment 255

8.1.2 Construction procedure 258

6 Design of improved ground by the deep mixing method

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

2.3 Engineering behavior of a group of individual columns 280

2.3.1 Stability of a group of individual columns 280

2.4 Summary of failure modes for a group of stabilized soil columns 291

3 Work flow of deep mixing and design 292

3.1 Work flow of deep mixing and geotechnical design 292

3.1.1 Work flow of deep mixing 292

3.1.2 Strategy – selection of column installation pattern 294

4 Design procedure for embankment support, group column type improved ground 295

4.1 Introduction 295

4.2 Basic concept 296

4.3 Design procedure 296

4.3.1 Design flow 296

4.3.2 Trial values for dimensions of improved ground 297

4.3.3 Examination of sliding failure 299

4.3.4 Slip circle analysis 300

4.3.5 Examination of horizontal displacement 302

4.3.6 Examination of bearing capacity 302

4.3.7 Examination of settlement 303

4.3.8 Amount of settlement for floating type improved ground 305

4.3.8.1 Rate of settlement 307

4.3.9 Important issues on design procedure 307

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

5.3.4 Examination of the external stability of improved ground 314

5.3.5 Examination of the internal stability of improved ground 320

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

6.3 Design procedure 331

6.3.1 Design flow 331

6.3.2 Examination of external stability of a superstructure 333

6.3.3 Setting of geometric conditions of improved ground 336

6.3.4 Evaluation of seismic coefficient for verification 336

6.3.5 Examination of the external stability of improved ground 337

6.3.6 Examination of internal stability of improved ground 344

6.3.7 Slip circle analysis 349

6.3.8 Examination of immediate and long term settlements 350

6.3.9 Determination of strength and specifications of stabilized soil 350

7 Design procedure of grid type improved ground for liquefaction prevention 350

7.1 Introduction 350

7.2 Basic concept 351

7.3 Design procedure 351

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

7.3.7 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

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

3.2.1 Laboratory mix test 374

3.2.2 Field trial test 374

3.2.3 Quality control during production 375

3.2.4 Quality verification 376

3.3 Technical issues on the QC/QA of stabilized soil 378

3.3.1 Technical issues with the laboratory mix test 378

3.3.2 Impact of diversified execution system on QC/QA 383

3.3.3 Verification techniques 385

4 QC/QA of improved ground – research needs 388

4.1 Embankment support by group of individual columns 388

4.1.1 QC/QA associated with current design practice 388

4.1.2 QC/QA for sophisticated design procedure considering the actual failure modes of group column type improved ground 389

4.1.3 Practitioners’ approach 390

4.2 Block type and wall type improvements for heavy structures 391

5 Summary 391

AppendixA Japanese laboratory mix test procedure

1 Introduction 395

2 Testing equipment 395

2.1 Equipment for making specimen 395

2.1.1 Mold 395

2.1.2 Mixer 396

2.1.3 Binder mixing tool 396

2.2 Soil and binder 397

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