Dedicationii Acknowledgementiii Table of contentsiv List of Tablesvii List of figuresviii List of Symbolsxii CHAPTER 1 INTRODUCTION1 1.1 Back ground information1 1.2 Objectives2 Structure2 CHAPTER 2 LITERATURE REVIEW4 2.1 Residual stress4 2.2 Bender element testing6 2.3 Axial extension test7 2.4 Identification of the yield point7 2.5 Related research8 2.6 Numerical analysis soil models9 2.6.1 Hardening Soil model (HS)9 2.6.2 Hardening Soil model with small-strain stiffness (HSsmall)10 2.7 Stiffness from one dimensional test11 2.8 Summary12 CHAPTER 3 EXPERIMENTAL APPARATUS, EQUIPMENT AND PROCEDURE22 3.1 Sampling22 3.2 Preparation of the sample22 3.3 Bender element testing23 3.4 Testing program23 3.4.1 Equipment for triaxial test23 3.4.1.1 Axial loading system24 3.4.1.2Digital pressure control system24 3.4.1.3Measurement systems24 3.4.1.4Procedure for setting up the soil sample and installing mini LVDT24 3.4.1.5Procedure for determining residual stress27 CHAPTER 4 RESULTS AND DISCUSSIONS43 4.1 Odometer test results43 4.2 Residual stress43 4.3 Parameters after consolidation stage47 4.4 Correction to axial extension test47 4.5 The stress and strain at the yield point49 4.5.1 Yielding on the stress path52 4.5.2 The yielding of soil as modeled in to various functions53 4.6 The stress, strain and the strength parameters at the failure point57 4.7 Stiffness parameters58 4.7.1 Bender element testing58 4.7.1 Parametric Study59 4.7.3 Triaxial and odometer tests62 CHAPTER 5 CONCLUSIONS AND RECCOMMENDATIONS103 5.1 Conclusions103 5.2 Recommendations for future research104 BIBLIOGRAPHY105 APPENDIX111 Basis of the equation developed here-in115 List of Tables Table 3.1 Basic soil index properties28 Table 4.1 Summary of odometer test results65 Table 4.3 Comparison between the calculated residual stress and the residual stress measured during the testing65 Table 4.4 Quantifying the level of disturbance66 Table 4.5 Classification of sample quality based on void ratio change during recompression (Lunne et al., 1997)66 Table 4.6 Parameters after consolidation66 Table 4.7 Distribution of the axial force between the soil, membrane and the pieces67 of filter paper67 Table 4.8 A comparison of the stress state at yield estimated from different curves67 All values are in kPa67 Table 4.9 summary of the stress state at yield and comparison of the stress state at yield to the stress state at failure67 Table 4.10 Comparison of prediction from different models68 Table 4.11 Summary of the stress state at and the strength parameters at failure68 Table 4.12 Input data for HS model against the experimental values69 Table 4.13 Input data for HSsmall model70 Table A1: Definition of the conic sections115 List of figures Fig. 2.1 Linear regression method to determine the residual effective stress-(Cho et al., 2007)13 Fig.2.2 Saturation using residual stress as back pressure-(Cho etal., 2007)13 Fig.2.3 Saturation using residual stress measured using suction- (Teng and Ou, 2011)14 Fig.2.4 Illustrating the stress relief concept and associated pore pressure changes during sampling14 Fig.2.5 Definition of the yield point (Jung et al., 2007)15 Fig.2.7 Comparison between the yield surface of Taipei silty clay and those from models- (Ou et al., 2010)15 Fig.2.8 Normalized average yield curves for soft soils (Diaz-Rodriguez et al., 1992)16 Fig.2.10 Representation of the yield surface curve on q-p’ plane by Estabragh et al.(2006) for unsaturated soil17 Fig.2.11 Representation of the yield surface curve for Chicago compressible clay on a normalized q-p’ plane by Kim et al. (2012)17 Fig.2.12 Length of stress path versus work per unit volume by Capotosto & Russo (2012)18 Fig.2.13 Yield surface curve, for saturated alluvial compacted soils by Capotosto and Russo (2012)18 Fig.2.14 Back analyzed curve against drained triaxial tests on loose Hostun sand (Plaxis19 3D manual)19 Fig.2.15 (a) shows characteristic of stiffness-strain behavior of soil with typical strain ranges for laboratory tests and structure – (Mair, 1993- plaxis 3D manual)19 (a)Results from Hardin Drnevich relationship compared to test data (Santos and Correia, 2001-plaxis 3D manual)20 (b)Effects of PI on shear stiffness, Vucetic and Dobry (1991)- Plaxis 3D manual20 Fig.2.16 TNEC HS model prediction, Aswin et al., 2010.21 Fig. 2.17 TNEC HSsmall model prediction, Aswin et al., 201021 Fig. 3.1 Plan of the sampling site (courtesy of Sino Geotechnology, Inc. Co.)28 Fig. 3.2 Cross section of the sampling site locating the sampling bore hole29 Figure 3.3 The soil profile showing SPTN values (Courtesy of Sino Geotechnology Inc. Co.)30 Fig. 3.4 (a) Sampling in progress30 (b) Sampling equipment30 Fig.3.5 (a) Operator attending to the tube sample31 (b) Sampling tubes31 Fig. 3.6 (a) Constant temperature humidity room31 (c)Temperature humidity monitoring device31 Fig. 3.7 Samples inside the constant temperature humidity room31 Fig. 3.8 (a) Direct Drive (D.D motor) servo motor32 (b) The pressure control system32 Fig. 3.9Working principle of bender element testing (Teng, 2010)32 Fig.3.10 The working components of the pressure control system33 Fig. 3.11 The Tilting and bedding errors may be reduced in this manner33 Fig. 3.12 (a) Orientation mould34 (b) Assembling the soil sample on to the orientation mould34 Fig. 3.13 Ultrasonic cleaner35 Fig. 3.14 (a) Membrane mould35 (b) O-ring caliper35 Fig. 3.15 Soil trimmer36 Fig. 3.16 The Trimming mold36 (a) upright36 (b) upside down36 Fig. 3.17 Mounting the membrane on to the sample37 Fig.3.18 Linear Variable Differential Transformer37 Fig. 3.19 (a) Mini LVDT axial displacement sensor 138 (b) Mini LVDT axial displacement sensor 238 (c) Mini LVDT radial displacement sensor38 Fig. 3.20 Detailed equipment set up and sample preparation39 Fig. 3.21 Sample Installation40 Fig. 3.22 Installation of LVDT and finishing up of the experimental set-up41 Fig. 3.23 Silicone oil42 (b) Oil injector42 Fig.3.24 Ultra sonic cleaner42 Fig. 4.1 Odometer test results72 Fig. 4.2 Evaluating sample quality for CIU_AC73 Fig. 4.3 Evaluating sample quality for CK0U_AC74 Fig. 4.4 Evaluating sample quality for CIU_AE75 Fig. 4.5 Evaluating sample quality for CID_AC76 Fig. 4.6 Decay of the secant Young’s modulus at small strain78 Fig. 4.7 Decay of the secant shear modulus at small strai80 Fig. 4.8 Deviator stress- axial strain curves (up to 0.2 strains) and point of maximum deviator stress81 Fig. 4.9 Deviator stress- axial strain curves (up to 0.05 strains)82 Fig. 4.10 Deviator stress- shear strain curves (up to 0.05strains)82 Fig. 4.11 Excess pore water pressure- axial strain curves83 Fig. 4.12 Strain energy versus p’ plots84 Fig. 4.13 Additional curves for drained testing85 Fig. 4.14 Localized sample failure suggesting equipment bias85 Fig. 4.15 Illustrating a way to identify yield point by minimizing observer and equipment bias86 Fig.4.16 Stress path test results88 Fig. 4.17Adopted yield curves for different models88 Fig. 4.18 The prediction equation against Jung et al.’s data (2007)89 Fig. 4.20 The prediction equation against Capotosto and Russo’s data (2012)90 Fig. 4.21 Bender element result90 Fig. 4.22Effects of 0.7 on the stress strain curve92 Fig. 4.23 Effects of G0ref on the stress strain curve94 Fig. 4.24 Effects of Eurref on the stress strain curve96 Fig. 4.25 Effects of E50ref on stress strain curve98 Fig. 4.26Effects of Eoedref on the stress strain curve100 Fig. 4.27 Back analyzed curves against the experimental curves102 Fig. A1: Flow chart for this study111 Fig. A2 Definition of initial secant modulus and 50% secant modulus under the standard drained axial compression test112 Fig.A4 Pictures of the failed samples113 Fig.A5 Excess pore water pressure at points of maximum deviator stress114 Dedicationii Acknowledgementiii Table of contentsiv List of Tablesvii List of figuresviii List of Symbolsxii CHAPTER 1 INTRODUCTION1 1.1 Back ground information1 1.2 Objectives2 Structure2 CHAPTER 2 LITERATURE REVIEW4 2.1 Residual stress4 2.2 Bender element testing6 2.3 Axial extension test7 2.4 Identification of the yield point7 2.5 Related research8 2.6 Numerical analysis soil models9 2.6.1 Hardening Soil model (HS)9 2.6.2 Hardening Soil model with small-strain stiffness (HSsmall)10 2.7 Stiffness from one dimensional test11 2.8 Summary12 CHAPTER 3 EXPERIMENTAL APPARATUS, EQUIPMENT AND PROCEDURE22 3.1 Sampling22 3.2 Preparation of the sample22 3.3 Bender element testing23 3.4 Testing program23 3.4.1 Equipment for triaxial test23 3.4.1.1 Axial loading system24 3.4.1.2Digital pressure control system24 3.4.1.3Measurement systems24 3.4.1.4Procedure for setting up the soil sample and installing mini LVDT24 3.4.1.5Procedure for determining residual stress27 CHAPTER 4 RESULTS AND DISCUSSIONS43 4.1 Odometer test results43 4.2 Residual stress43 4.3 Parameters after consolidation stage47 4.4 Correction to axial extension test47 4.5 The stress and strain at the yield point49 4.5.1 Yielding on the stress path52 4.5.2 The yielding of soil as modeled in to various functions53 4.6 The stress, strain and the strength parameters at the failure point57 4.7 Stiffness parameters58 4.7.1 Bender element testing58 4.7.1 Parametric Study59 4.7.3 Triaxial and odometer tests62 CHAPTER 5 CONCLUSIONS AND RECCOMMENDATIONS103 5.1 Conclusions103 5.2 Recommendations for future research104 BIBLIOGRAPHY105 APPENDIX111 Basis of the equation developed here-in115 List of Tables Table 3.1 Basic soil index properties28 Table 4.1 Summary of odometer test results65 Table 4.3 Comparison between the calculated residual stress and the residual stress measured during the testing65 Table 4.4 Quantifying the level of disturbance66 Table 4.5 Classification of sample quality based on void ratio change during recompression (Lunne et al., 1997)66 Table 4.6 Parameters after consolidation66 Table 4.7 Distribution of the axial force between the soil, membrane and the pieces67 of filter paper67 Table 4.8 A comparison of the stress state at yield estimated from different curves67 All values are in kPa67 Table 4.9 summary of the stress state at yield and comparison of the stress state at yield to the stress state at failure67 Table 4.10 Comparison of prediction from different models68 Table 4.11 Summary of the stress state at and the strength parameters at failure68 Table 4.12 Input data for HS model against the experimental values69 Table 4.13 Input data for HSsmall model70 Table A1: Definition of the conic sections115 List of figures Fig. 2.1 Linear regression method to determine the residual effective stress-(Cho et al., 2007)13 Fig.2.2 Saturation using residual stress as back pressure-(Cho etal., 2007)13 Fig.2.3 Saturation using residual stress measured using suction- (Teng and Ou, 2011)14 Fig.2.4 Illustrating the stress relief concept and associated pore pressure changes during sampling14 Fig.2.5 Definition of the yield point (Jung et al., 2007)15 Fig.2.7 Comparison between the yield surface of Taipei silty clay and those from models- (Ou et al., 2010)15 Fig.2.8 Normalized average yield curves for soft soils (Diaz-Rodriguez et al., 1992)16 Fig.2.10 Representation of the yield surface curve on q-p’ plane by Estabragh et al.(2006) for unsaturated soil17 Fig.2.11 Representation of the yield surface curve for Chicago compressible clay on a normalized q-p’ plane by Kim et al. (2012)17 Fig.2.12 Length of stress path versus work per unit volume by Capotosto & Russo (2012)18 Fig.2.13 Yield surface curve, for saturated alluvial compacted soils by Capotosto and Russo (2012)18 Fig.2.14 Back analyzed curve against drained triaxial tests on loose Hostun sand (Plaxis19 3D manual)19 Fig.2.15 (a) shows characteristic of stiffness-strain behavior of soil with typical strain ranges for laboratory tests and structure – (Mair, 1993- plaxis 3D manual)19 (a)Results from Hardin Drnevich relationship compared to test data (Santos and Correia, 2001-plaxis 3D manual)20 (b)Effects of PI on shear stiffness, Vucetic and Dobry (1991)- Plaxis 3D manual20 Fig.2.16 TNEC HS model prediction, Aswin et al., 2010.21 Fig. 2.17 TNEC HSsmall model prediction, Aswin et al., 201021 Fig. 3.1 Plan of the sampling site (courtesy of Sino Geotechnology, Inc. Co.)28 Fig. 3.2 Cross section of the sampling site locating the sampling bore hole29 Figure 3.3 The soil profile showing SPTN values (Courtesy of Sino Geotechnology Inc. Co.)30 Fig. 3.4 (a) Sampling in progress30 (b) Sampling equipment30 Fig.3.5 (a) Operator attending to the tube sample31 (b) Sampling tubes31 Fig. 3.6 (a) Constant temperature humidity room31 (c)Temperature humidity monitoring device31 Fig. 3.7 Samples inside the constant temperature humidity room31 Fig. 3.8 (a) Direct Drive (D.D motor) servo motor32 (b) The pressure control system32 Fig. 3.9Working principle of bender element testing (Teng, 2010)32 Fig.3.10 The working components of the pressure control system33 Fig. 3.11 The Tilting and bedding errors may be reduced in this manner33 Fig. 3.12 (a) Orientation mould34 (b) Assembling the soil sample on to the orientation mould34 Fig. 3.13 Ultrasonic cleaner35 Fig. 3.14 (a) Membrane mould35 (b) O-ring caliper35 Fig. 3.15 Soil trimmer36 Fig. 3.16 The Trimming mold36 (a) upright36 (b) upside down36 Fig. 3.17 Mounting the membrane on to the sample37 Fig.3.18 Linear Variable Differential Transformer37 Fig. 3.19 (a) Mini LVDT axial displacement sensor 138 (b) Mini LVDT axial displacement sensor 238 (c) Mini LVDT radial displacement sensor38 Fig. 3.20 Detailed equipment set up and sample preparation39 Fig. 3.21 Sample Installation40 Fig. 3.22 Installation of LVDT and finishing up of the experimental set-up41 Fig. 3.23 Silicone oil42 (b) Oil injector42 Fig.3.24 Ultra sonic cleaner42 Fig. 4.1 Odometer test results72 Fig. 4.2 Evaluating sample quality for CIU_AC73 Fig. 4.3 Evaluating sample quality for CK0U_AC74 Fig. 4.4 Evaluating sample quality for CIU_AE75 Fig. 4.5 Evaluating sample quality for CID_AC76 Fig. 4.6 Decay of the secant Young’s modulus at small strain78 Fig. 4.7 Decay of the secant shear modulus at small strai80 Fig. 4.8 Deviator stress- axial strain curves (up to 0.2 strains) and point of maximum deviator stress81 Fig. 4.9 Deviator stress- axial strain curves (up to 0.05 strains)82 Fig. 4.10 Deviator stress- shear strain curves (up to 0.05strains)82 Fig. 4.11 Excess pore water pressure- axial strain curves83 Fig. 4.12 Strain energy versus p’ plots84 Fig. 4.13 Additional curves for drained testing85 Fig. 4.14 Localized sample failure suggesting equipment bias85 Fig. 4.15 Illustrating a way to identify yield point by minimizing observer and equipment bias86 Fig.4.16 Stress path test results88 Fig. 4.17Adopted yield curves for different models88 Fig. 4.18 The prediction equation against Jung et al.’s data (2007)89 Fig. 4.20 The prediction equation against Capotosto and Russo’s data (2012)90 Fig. 4.21 Bender element result90 Fig. 4.22Effects of 0.7 on the stress strain curve92 Fig. 4.23 Effects of G0ref on the stress strain curve94 Fig. 4.24 Effects of Eurref on the stress strain curve96 Fig. 4.25 Effects of E50ref on stress strain curve98 Fig. 4.26Effects of Eoedref on the stress strain curve100 Fig. 4.27 Back analyzed curves against the experimental curves102 Fig. A1: Flow chart for this study111 Fig. A2 Definition of initial secant modulus and 50% secant modulus under the standard drained axial compression test112 Fig.A4 Pictures of the failed samples113 Fig.A5 Excess pore water pressure at points of maximum deviator stress114 Dedicationii Acknowledgementiii Table of contentsiv List of Tablesvii List of figuresviii List of Symbolsxii CHAPTER 1 INTRODUCTION1 1.1 Back ground information1 1.2 Objectives2 Structure2 CHAPTER 2 LITERATURE REVIEW4 2.1 Residual stress4 2.2 Bender element testing6 2.3 Axial extension test7 2.4 Identification of the yield point7 2.5 Related research8 2.6 Numerical analysis soil models9 2.6.1 Hardening Soil model (HS)9 2.6.2 Hardening Soil model with small-strain stiffness (HSsmall)10 2.7 Stiffness from one dimensional test11 2.8 Summary12 CHAPTER 3 EXPERIMENTAL APPARATUS, EQUIPMENT AND PROCEDURE22 3.1 Sampling22 3.2 Preparation of the sample22 3.3 Bender element testing23 3.4 Testing program23 3.4.1 Equipment for triaxial test23 3.4.1.1 Axial loading system24 3.4.1.2Digital pressure control system24 3.4.1.3Measurement systems24 3.4.1.4Procedure for setting up the soil sample and installing mini LVDT24 3.4.1.5Procedure for determining residual stress27 CHAPTER 4 RESULTS AND DISCUSSIONS43 4.1 Odometer test results43 4.2 Residual stress43 4.3 Parameters after consolidation stage47 4.4 Correction to axial extension test47 4.5 The stress and strain at the yield point49 4.5.1 Yielding on the stress path52 4.5.2 The yielding of soil as modeled in to various functions53 4.6 The stress, strain and the strength parameters at the failure point57 4.7 Stiffness parameters58 4.7.1 Bender element testing58 4.7.1 Parametric Study59 4.7.3 Triaxial and odometer tests62 CHAPTER 5 CONCLUSIONS AND RECCOMMENDATIONS103 5.1 Conclusions103 5.2 Recommendations for future research104 BIBLIOGRAPHY105 APPENDIX111 Basis of the equation developed here-in115 List of Tables Table 3.1 Basic soil index properties28 Table 4.1 Summary of odometer test results65 Table 4.3 Comparison between the calculated residual stress and the residual stress measured during the testing65 Table 4.4 Quantifying the level of disturbance66 Table 4.5 Classification of sample quality based on void ratio change during recompression (Lunne et al., 1997)66 Table 4.6 Parameters after consolidation66 Table 4.7 Distribution of the axial force between the soil, membrane and the pieces67 of filter paper67 Table 4.8 A comparison of the stress state at yield estimated from different curves67 All values are in kPa67 Table 4.9 summary of the stress state at yield and comparison of the stress state at yield to the stress state at failure67 Table 4.10 Comparison of prediction from different models68 Table 4.11 Summary of the stress state at and the strength parameters at failure68 Table 4.12 Input data for HS model against the experimental values69 Table 4.13 Input data for HSsmall model70 Table A1: Definition of the conic sections115 List of figures Fig. 2.1 Linear regression method to determine the residual effective stress-(Cho et al., 2007)13 Fig.2.2 Saturation using residual stress as back pressure-(Cho etal., 2007)13 Fig.2.3 Saturation using residual stress measured using suction- (Teng and Ou, 2011)14 Fig.2.4 Illustrating the stress relief concept and associated pore pressure changes during sampling14 Fig.2.5 Definition of the yield point (Jung et al., 2007)15 Fig.2.7 Comparison between the yield surface of Taipei silty clay and those from models- (Ou et al., 2010)15 Fig.2.8 Normalized average yield curves for soft soils (Diaz-Rodriguez et al., 1992)16 Fig.2.10 Representation of the yield surface curve on q-p’ plane by Estabragh et al.(2006) for unsaturated soil17 Fig.2.11 Representation of the yield surface curve for Chicago compressible clay on a normalized q-p’ plane by Kim et al. (2012)17 Fig.2.12 Length of stress path versus work per unit volume by Capotosto & Russo (2012)18 Fig.2.13 Yield surface curve, for saturated alluvial compacted soils by Capotosto and Russo (2012)18 Fig.2.14 Back analyzed curve against drained triaxial tests on loose Hostun sand (Plaxis19 3D manual)19 Fig.2.15 (a) shows characteristic of stiffness-strain behavior of soil with typical strain ranges for laboratory tests and structure – (Mair, 1993- plaxis 3D manual)19 (a)Results from Hardin Drnevich relationship compared to test data (Santos and Correia, 2001-plaxis 3D manual)20 (b)Effects of PI on shear stiffness, Vucetic and Dobry (1991)- Plaxis 3D manual20 Fig.2.16 TNEC HS model prediction, Aswin et al., 2010.21 Fig. 2.17 TNEC HSsmall model prediction, Aswin et al., 201021 Fig. 3.1 Plan of the sampling site (courtesy of Sino Geotechnology, Inc. Co.)28 Fig. 3.2 Cross section of the sampling site locating the sampling bore hole29 Figure 3.3 The soil profile showing SPTN values (Courtesy of Sino Geotechnology Inc. Co.)30 Fig. 3.4 (a) Sampling in progress30 (b) Sampling equipment30 Fig.3.5 (a) Operator attending to the tube sample31 (b) Sampling tubes31 Fig. 3.6 (a) Constant temperature humidity room31 (c)Temperature humidity monitoring device31 Fig. 3.7 Samples inside the constant temperature humidity room31 Fig. 3.8 (a) Direct Drive (D.D motor) servo motor32 (b) The pressure control system32 Fig. 3.9Working principle of bender element testing (Teng, 2010)32 Fig.3.10 The working components of the pressure control system33 Fig. 3.11 The Tilting and bedding errors may be reduced in this manner33 Fig. 3.12 (a) Orientation mould34 (b) Assembling the soil sample on to the orientation mould34 Fig. 3.13 Ultrasonic cleaner35 Fig. 3.14 (a) Membrane mould35 (b) O-ring caliper35 Fig. 3.15 Soil trimmer36 Fig. 3.16 The Trimming mold36 (a) upright36 (b) upside down36 Fig. 3.17 Mounting the membrane on to the sample37 Fig.3.18 Linear Variable Differential Transformer37 Fig. 3.19 (a) Mini LVDT axial displacement sensor 138 (b) Mini LVDT axial displacement sensor 238 (c) Mini LVDT radial displacement sensor38 Fig. 3.20 Detailed equipment set up and sample preparation39 Fig. 3.21 Sample Installation40 Fig. 3.22 Installation of LVDT and finishing up of the experimental set-up41 Fig. 3.23 Silicone oil42 (b) Oil injector42 Fig.3.24 Ultra sonic cleaner42 Fig. 4.1 Odometer test results72 Fig. 4.2 Evaluating sample quality for CIU_AC73 Fig. 4.3 Evaluating sample quality for CK0U_AC74 Fig. 4.4 Evaluating sample quality for CIU_AE75 Fig. 4.5 Evaluating sample quality for CID_AC76 Fig. 4.6 Decay of the secant Young’s modulus at small strain78 Fig. 4.7 Decay of the secant shear modulus at small strai80 Fig. 4.8 Deviator stress- axial strain curves (up to 0.2 strains) and point of maximum deviator stress81 Fig. 4.9 Deviator stress- axial strain curves (up to 0.05 strains)82 Fig. 4.10 Deviator stress- shear strain curves (up to 0.05strains)82 Fig. 4.11 Excess pore water pressure- axial strain curves83 Fig. 4.12 Strain energy versus p’ plots84 Fig. 4.13 Additional curves for drained testing85 Fig. 4.14 Localized sample failure suggesting equipment bias85 Fig. 4.15 Illustrating a way to identify yield point by minimizing observer and equipment bias86 Fig.4.16 Stress path test results88 Fig. 4.17Adopted yield curves for different models88 Fig. 4.18 The prediction equation against Jung et al.’s data (2007)89 Fig. 4.20 The prediction equation against Capotosto and Russo’s data (2012)90 Fig. 4.21 Bender element result90 Fig. 4.22Effects of 0.7 on the stress strain curve92 Fig. 4.23 Effects of G0ref on the stress strain curve94 Fig. 4.24 Effects of Eurref on the stress strain curve96 Fig. 4.25 Effects of E50ref on stress strain curve98 Fig. 4.26Effects of Eoedref on the stress strain curve100 Fig. 4.27 Back analyzed curves against the experimental curves102 Fig. A1: Flow chart for this study111 Fig. A2 Definition of initial secant modulus and 50% secant modulus under the standard drained axial compression test112 Fig.A4 Pictures of the failed samples113 Fig.A5 Excess pore water pressure at points of maximum deviator stress114 Dedicationii Acknowledgementiii Table of contentsiv List of Tablesvii List of figuresviii List of Symbolsxii CHAPTER 1 INTRODUCTION1 1.1 Back ground information1 1.2 Objectives2 Structure2 CHAPTER 2 LITERATURE REVIEW4 2.1 Residual stress4 2.2 Bender element testing6 2.3 Axial extension test7 2.4 Identification of the yield point7 2.5 Related research8 2.6 Numerical analysis soil models9 2.6.1 Hardening Soil model (HS)9 2.6.2 Hardening Soil model with small-strain stiffness (HSsmall)10 2.7 Stiffness from one dimensional test11 2.8 Summary12 CHAPTER 3 EXPERIMENTAL APPARATUS, EQUIPMENT AND PROCEDURE22 3.1 Sampling22 3.2 Preparation of the sample22 3.3 Bender element testing23 3.4 Testing program23 3.4.1 Equipment for triaxial test23 3.4.1.1 Axial loading system24 3.4.1.2Digital pressure control system24 3.4.1.3Measurement systems24 3.4.1.4Procedure for setting up the soil sample and installing mini LVDT24 3.4.1.5Procedure for determining residual stress27 CHAPTER 4 RESULTS AND DISCUSSIONS43 4.1 Odometer test results43 4.2 Residual stress43 4.3 Parameters after consolidation stage47 4.4 Correction to axial extension test47 4.5 The stress and strain at the yield point49 4.5.1 Yielding on the stress path52 4.5.2 The yielding of soil as modeled in to various functions53 4.6 The stress, strain and the strength parameters at the failure point57 4.7 Stiffness parameters58 4.7.1 Bender element testing58 4.7.1 Parametric Study59 4.7.3 Triaxial and odometer tests62 CHAPTER 5 CONCLUSIONS AND RECCOMMENDATIONS103 5.1 Conclusions103 5.2 Recommendations for future research104 BIBLIOGRAPHY105 APPENDIX111 Basis of the equation developed here-in115 List of Tables Table 3.1 Basic soil index properties28 Table 4.1 Summary of odometer test results65 Table 4.3 Comparison between the calculated residual stress and the residual stress measured during the testing65 Table 4.4 Quantifying the level of disturbance66 Table 4.5 Classification of sample quality based on void ratio change during recompression (Lunne et al., 1997)66 Table 4.6 Parameters after consolidation66 Table 4.7 Distribution of the axial force between the soil, membrane and the pieces67 of filter paper67 Table 4.8 A comparison of the stress state at yield estimated from different curves67 All values are in kPa67 Table 4.9 summary of the stress state at yield and comparison of the stress state at yield to the stress state at failure67 Table 4.10 Comparison of prediction from different models68 Table 4.11 Summary of the stress state at and the strength parameters at failure68 Table 4.12 Input data for HS model against the experimental values69 Table 4.13 Input data for HSsmall model70 Table A1: Definition of the conic sections115 List of figures Fig. 2.1 Linear regression method to determine the residual effective stress-(Cho et al., 2007)13 Fig.2.2 Saturation using residual stress as back pressure-(Cho etal., 2007)13 Fig.2.3 Saturation using residual stress measured using suction- (Teng and Ou, 2011)14 Fig.2.4 Illustrating the stress relief concept and associated pore pressure changes during sampling14 Fig.2.5 Definition of the yield point (Jung et al., 2007)15 Fig.2.7 Comparison between the yield surface of Taipei silty clay and those from models- (Ou et al., 2010)15 Fig.2.8 Normalized average yield curves for soft soils (Diaz-Rodriguez et al., 1992)16 Fig.2.10 Representation of the yield surface curve on q-p’ plane by Estabragh et al.(2006) for unsaturated soil17 Fig.2.11 Representation of the yield surface curve for Chicago compressible clay on a normalized q-p’ plane by Kim et al. (2012)17 Fig.2.12 Length of stress path versus work per unit volume by Capotosto & Russo (2012)18 Fig.2.13 Yield surface curve, for saturated alluvial compacted soils by Capotosto and Russo (2012)18 Fig.2.14 Back analyzed curve against drained triaxial tests on loose Hostun sand (Plaxis19 3D manual)19 Fig.2.15 (a) shows characteristic of stiffness-strain behavior of soil with typical strain ranges for laboratory tests and structure – (Mair, 1993- plaxis 3D manual)19 (a)Results from Hardin Drnevich relationship compared to test data (Santos and Correia, 2001-plaxis 3D manual)20 (b)Effects of PI on shear stiffness, Vucetic and Dobry (1991)- Plaxis 3D manual20 Fig.2.16 TNEC HS model prediction, Aswin et al., 2010.21 Fig. 2.17 TNEC HSsmall model prediction, Aswin et al., 201021 Fig. 3.1 Plan of the sampling site (courtesy of Sino Geotechnology, Inc. Co.)28 Fig. 3.2 Cross section of the sampling site locating the sampling bore hole29 Figure 3.3 The soil profile showing SPTN values (Courtesy of Sino Geotechnology Inc. Co.)30 Fig. 3.4 (a) Sampling in progress30 (b) Sampling equipment30 Fig.3.5 (a) Operator attending to the tube sample31 (b) Sampling tubes31 Fig. 3.6 (a) Constant temperature humidity room31 (c)Temperature humidity monitoring device31 Fig. 3.7 Samples inside the constant temperature humidity room31 Fig. 3.8 (a) Direct Drive (D.D motor) servo motor32 (b) The pressure control system32 Fig. 3.9Working principle of bender element testing (Teng, 2010)32 Fig.3.10 The working components of the pressure control system33 Fig. 3.11 The Tilting and bedding errors may be reduced in this manner33 Fig. 3.12 (a) Orientation mould34 (b) Assembling the soil sample on to the orientation mould34 Fig. 3.13 Ultrasonic cleaner35 Fig. 3.14 (a) Membrane mould35 (b) O-ring caliper35 Fig. 3.15 Soil trimmer36 Fig. 3.16 The Trimming mold36 (a) upright36 (b) upside down36 Fig. 3.17 Mounting the membrane on to the sample37 Fig.3.18 Linear Variable Differential Transformer37 Fig. 3.19 (a) Mini LVDT axial displacement sensor 138 (b) Mini LVDT axial displacement sensor 238 (c) Mini LVDT radial displacement sensor38 Fig. 3.20 Detailed equipment set up and sample preparation39 Fig. 3.21 Sample Installation40 Fig. 3.22 Installation of LVDT and finishing up of the experimental set-up41 Fig. 3.23 Silicone oil42 (b) Oil injector42 Fig.3.24 Ultra sonic cleaner42 Fig. 4.1 Odometer test results72 Fig. 4.2 Evaluating sample quality for CIU_AC73 Fig. 4.3 Evaluating sample quality for CK0U_AC74 Fig. 4.4 Evaluating sample quality for CIU_AE75 Fig. 4.5 Evaluating sample quality for CID_AC76 Fig. 4.6 Decay of the secant Young’s modulus at small strain78 Fig. 4.7 Decay of the secant shear modulus at small strai80 Fig. 4.8 Deviator stress- axial strain curves (up to 0.2 strains) and point of maximum deviator stress81 Fig. 4.9 Deviator stress- axial strain curves (up to 0.05 strains)82 Fig. 4.10 Deviator stress- shear strain curves (up to 0.05strains)82 Fig. 4.11 Excess pore water pressure- axial strain curves83 Fig. 4.12 Strain energy versus p’ plots84 Fig. 4.13 Additional curves for drained testing85 Fig. 4.14 Localized sample failure suggesting equipment bias85 Fig. 4.15 Illustrating a way to identify yield point by minimizing observer and equipment bias86 Fig.4.16 Stress path test results88 Fig. 4.17Adopted yield curves for different models88 Fig. 4.18 The prediction equation against Jung et al.’s data (2007)89 Fig. 4.20 The prediction equation against Capotosto and Russo’s data (2012)90 Fig. 4.21 Bender element result90 Fig. 4.22Effects of 0.7 on the stress strain curve92 Fig. 4.23 Effects of G0ref on the stress strain curve94 Fig. 4.24 Effects of Eurref on the stress strain curve96 Fig. 4.25 Effects of E50ref on stress strain curve98 Fig. 4.26Effects of Eoedref on the stress strain curve100 Fig. 4.27 Back analyzed curves against the experimental curves102 Fig. A1: Flow chart for this study111 Fig. A2 Definition of initial secant modulus and 50% secant modulus under the standard drained axial compression test112 Fig.A4 Pictures of the failed samples113 Fig.A5 Excess pore water pressure at points of maximum deviator stress114