Modelling with Transparent Soils (eBook)

Contents 6
Introduction to Transparent Soils 17
Background 17
Available Transparent Soils 18
Objectives 19
Organization of This Book 19
References 19
Optical Techniques in Geotechnical Engineering 21
Introduction 21
Imaging Applications in Geotechnical Engineering 21
Soil Stress Measurements 22
Soil Deformation Measurements 22
Soil Fabric and Void Characterization 25
Soil Classification and Grain Size Distribution Analysis 27
Imaging Techniques in Geoenvironmental Studies 28
Example Applications of Imaging Techniques in Civil Engineering 28
Pavement Crack Measurement 28
Traffic Analysis and Control 29
Concrete Morphology and Micro-cracks 29
Summary 29
References 30
Introduction to Light and Optics 35
Introduction 35
Nature of Light 35
Propagation of Light in a Matter 36
Refraction of Light 37
Reflection of Light 38
Light in a Granular Medium 38
Basic Definitions 39
Speckle Effect 39
Coherent Light 39
Polarized Light 39
Polarizers 40
Birefringence 40
References 41
Optical Measurement of Strain and Stress 42
Introduction 42
Target Tracking 43
Digital Image Correlation 43
Interferometry 44
Holographic Interferometry (HI) 45
Speckle Interferometry 46
Photoelasticity 52
Theory 52
Photoelasticity of Transparent Synthetic Soils 54
Cross Tomography 56
Theory 56
Cross Tomography in Transparent Synthetic Soils 57
Summary 58
References 58
Geotechnical Properties of Transparent Silica Powders 60
Introduction 60
What Is Amorphous Silica? 60
Use of Amorphous Silica in Experimental Modeling 61
Material Description 62
Physical Properties of Amorphous Silica 62
Matched Refractive Index Pore Fluids 63
Sample Preparation 64
Undrained Triaxial Tests 65
Normally Consolidated Behavior 67
Overconsolidated Behavior 72
Drained Triaxial Tests 76
Elastic Properties of Amorphous Silica 81
Consolidation Properties 82
Consolidation Indices 83
Consolidation Behavior 85
Settlement Components 86
Pore Pressure Dissipation 87
Compression Isochrones 92
Ko vs. Isotropic Consolidation 93
Permeability Properties 94
Permeability with Void Ratio 94
Permeability with Vertical Pressure 94
Permeability with Material Type 95
Conclusions 96
References 96
Geotechnical Properties of Silica Gels 100
Background 100
What Is Silica Gel? 100
Basic Chemical Properties and Chemical Preparation 102
Physical Properties 103
Particle Structure 103
Specific Gravity and Unit Weight 103
Void Ratio 104
Particle Size Distribution and Uniformity 104
Static Geotechnical Properties of Silica Gel 105
Shear Strength 105
Modulus of Elasticity 113
Compressibility 117
Hydraulic Conductivity 119
Dynamic Properties of Silica Gel 122
Testing Program and Sample Preparation 122
Shear Modulus of Silica Gel 124
Damping Ratio of Silica Gel 127
Comparison with Results of Sands and Gravels 128
Modeling Capabilities of Transparent Soils 128
Recommended Future Work 128
References 129
Geotechnical Properties of Aquabeads 131
Introduction 131
What Is Aquabeads? 132
Grain Size Distribution 134
Hydraulic Conductivity of Aquabeads 135
Compressibility of Aquabeads 137
Void Ratio 137
Consolidation Behavior 137
Consolidation Indices 138
Strength of Aquabeads 141
Yield Stress 141
Yield Stress Measurement 142
Yield Stress Calculation 142
Yield Strength of Aquabeads 143
Comparison to the Yield Stresses of Natural Soils 146
Conclusions 148
References 148
Digital Image Correlation 150
Introduction 150
Digital Imaging 150
Digital Image Format 150
Digital Image Resolution 152
Digital Image Compression 152
Motion Estimation Methods 152
The Fourier Method 153
The Differential Method 153
The Matching Method 154
Digital Image Correlation 155
Discrete Cross-Correlation 155
Zero-Meaned Normalized Cross-Correlation 155
Execution of Cross-Correlation Using FFT 157
How DIC Works 158
Sub-Pixel Resolution 162
DIC Error Analysis 162
Conventional DIC 162
Error Analysis 163
Particle Density 163
Interrogation Windows Size 164
Adaptive Cross-Correlation 164
Variable Window Size 165
Window Offset 165
ACC Procedure 165
Comparison between DIC and ACC 167
Verification of DIC and ACC Algorithms 167
Performance of DIC and ACC Algorithms for Physical Movements 172
Conclusions 175
References 176
Application of DIC for Measuring Deformations in Transparent Soils 178
Introduction and Motivation 178
Setup for DIC in Transparent Synthetic Soil Models 179
Transparent Soil Model 180
Laser Beam 181
Line Generator 181
Digital Camera 181
Correlation Algorithm 182
Calibration of DIC for Deformation Measurement in Transparent Soils 182
Calibration Methodology 182
Calibration Results 183
Other Errors 186
Reflection 186
Alignment Error 186
Focus Errors 187
Out-of-Plane and Rotational Movement Errors 187
Application of DIC in Modeling Soil Structure Interaction 187
DIC Analysis Results 187
Comparison with FEM 188
System Limitations 191
Conclusions 191
References 191
Validation of Measured 2D Deformations 193
Introduction 193
Test Program 194
Proposed Method 194
Set-Up 195
Test Program 195
Comparison under Dry Loose Condition 196
Failure Mode 196
Displacement Field 197
Maximum Horizontal Displacement 199
Settlement Distribution 201
Strain Field 202
Volume Strain 204
Vertical Strain 209
Comparison under Dry Dense Condition 210
Settlement Comparison 213
Maximum Horizontal Displacement 213
Comparison under Saturated Dense Condition 216
2D Deformation Measurement in Transparent Soil 216
Model Preparation 217
Displacement Field 217
Vertical Displacement 218
Maximum Horizontal Displacement 221
Maximum Shear Strain 224
Modeling Stratified Soils Using Transparent Surrogates 226
Modeling Loose “Sand” Over Dense “Sand” 227
Modeling “Sand” over Soft “Clay” 229
Deformations Inside Transparent Synthetic Soil Models 232
Internal Deformations in Silica Gel Representing Sand 232
Internal Deformations in Amorphous Silica Powder Representing Clay 233
Conclusions and Recommendations 236
References 236
3D Deformation Measurement 238
Introduction 238
3D Measurements 238
Methodology 239
Test Setup 240
Digital Image Processing 242
Test Procedure 243
Displacement Field Analysis 247
Strain Field Analysis 252
Displacement and Strain Development 257
Displacement Field 257
Strain Field 258
Error Analysis 260
Result Analysis 260
Image Distortion Analysis 264
Speckle Stability over Time 265
Linear Stage Error 265
Conclusions and Recommendations 268
References 268
2D Flow in Transparent Synthetic Soils 270
Introduction 270
Flow Tests Using Silica Gel 271
Materials 271
Sample Preparation 272
Flow Equipment Setup 272
Optical Measurements 272
Calibration of Concentration 273
Chromatographic Separation 274
Image Analysis 276
Breakthrough Curve 280
Characterizing the Properties of Silica Gel 281
Flow Test Using Fused Silica 283
Transparency Degradation in Silica Gel 283
Fused Silica 284
Immiscible Flow Test 287
Flow Tests Using Aquabeads 288
Materials 288
Concentration Calibration 288
Packing of Aquabeads for 2D Flow Test 288
Flow System Setup and Effluent Collection 289
Optical System and Image Analysis 290
Miscible Flow Tests 290
Multi-phase Flow 293
Hydraulic Characteristics of Aquabeads 293
Modeling of 2D Surfactant Flushing Using Aquabeads 296
Phase Behavior Tests 297
Test Setup 298
Recovery of Mineral Oil 298
Recovery of Motor Oil 299
Conclusions 302
References 302
Epilogue 304
The Transparent Soil Story 304
Capabilities of Available Transparent Soils 306
Limitations of the Technology 306
Recommendations for Future Research 307
Potential Applications 308
References 309
Appendix 310
References 324
Index 338