Thạc Sĩ Small and large strain monitoring of unsaturated soil behavior by

Table of Contents
Acknowledgments . ii
Abstract v
Chapter 1. Introduction .1
1.1 Evaluation of Small Strain Stiffness under Ko-Conditions in Dry and Unsaturated Soils 1
1.2 Evaluation of Small and Large Stiffness under Multi-axial State of Stress
Conditions in Unsaturated Soil with Suction Control 1
1.3 Organization .2
Chapter 2. Mechanical Behavior of Unsaturated Soils at Small and Large Strain .4
2.1 Introduction 4
2.2 Effective Stress Concept in Unsaturated Soils .5
2.3 Stress-Strain Behavior of Unsaturated Soils 10
2.4 Experimental Determination of the Stress State Variables 14
2.5 Volume Changes in Unsaturated Soils 17
2.6 Swell/Shrink Behavior .21
2.7 Measurement of Suction 24
2.8 Small Strain Parameter of Soils .24
2.9 Elastic Wave Propagation 25
2.10 Elastic Wave Measurement Techniques 28
2.11 Previous Work on Elastic Wave Measurement Using Bender Elements 32
2.11.1 Use of Bender Elements on Saturated Soils 32
2.11.2 Use of Bender Elements on Unsaturated Soils 39
2.12 Summary 40
Chapter 3. Testing Under Ko-Conditions 42
3.1 Introduction 42
3.2 Soil Characterization 42
3.2.1 Determination of Grain Size Distribution 42
3.2.2 Determination of Specific Gravity .43
3.2.3 Determination of Soil Specific Surface .43
3.3. Description of the Testing Setup .44
3.3.1 Shear Wave Velocity Monitoring 44
3.3.2 Monitoring Soil Matric Suction .48
3.3.3 Specimen Preparation and Testing Procedure .49
3.4. Test Results .53
3.4.1 Tested Soil Properties 53
3.4.2 Tested Results 54
3.5. Summary .71
Chapter 4. Multiaxial Testing on Silt Specimens 72
4.1. Introduction .72
4.2. True Triaxial Testing 72
iv
4.3. Testing Program 78
4.3.1 Loading Rate Selection 78
4.3.2 Matric Suction Regulation .79
4.3.3 Material and Testing Methodology 79
4.4. Results .83
4.4.1 Results from Triaxial Compression (TC) Tests - Small Strain Data .83
4.4.2 Results from Triaxial Compression (TC) Tests - Large Strain data 87
4.4.3 Results from Conventional Triaxial Compression (CTC) Tests
Small Strain Data .89
4.4.4 Results from Conventional Triaxial Compression (CTC) Tests
Large Strain Data .94
4.5 Repeatability 96
4.6 Summary 97
Chapter 5. Multiaxial Testing on Sand Specimens .98
5.1 Introduction 98
5.2 Testing Program .98
5.3 Results 99
5.3.1 Results from Triaxial Compression (TC) Tests - Small Strain Data .99
5.3.2 Results from Triaxial Compression (TC) Tests - Large Strain Data .103
5.3.3 Results from Conventional Triaxial (CTC) Compression Tests
Small Strain Data .104
5.3.4 Results from Conventional Triaxial Compression Tests (CTC)
Large Strain Data .108
5.4 Repeatability 110
5.5 Summary 110
Chapter 6. Interpretation and Discussion of Results 112
6.1 Modified Oedometer Device 112
6.1.1 Proposed Model for the Evaluation of S-wave Velocity .114
6.1.2 Determination of Stress Anisotropy Using S-wave Velocity 119
6.2 Modified True Triaxial Device 120
6.2.1 Small Strain Analysis .120
6.2.2 Large Strain Analysis .125
Chapter 7. Conclusions and Recommendations for Future Work 130
7.1 Ko-condition Testing Results .130
7.2 Multiaxial Testing Results .131
7.3 Recommendations for Future Work .132
References .133
Appendix A. Travel Time Data: Clayey Silt 141
Appendix B. Travel Time Data: Silica Sand .153
Vita 165