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Constitutive modelling and instabilities of soil behaviour
264A
PROPERTIESDEFORMATION
Deformation and strength characteristics 956100 Inversion of the elastic parameters of a layered medium Pei-Ling Liu, Chong-Dao Tsai & Tsung-Tsong Wu, Journal - Acoustical Society of America, 97(3), 1995, pp 1687-1693. This paper presents a method for constructing the elastic parameters of a layered elastic medium such as the wave velocities, densities, and thicknesses of the layers. The inverse problem is formulated as optimization problem in which the norm of the discrepancies between the measured and calculated surface response is minimized. The experiments were conducted on a thin plate. The impact of a steel ball was adopted to generate a vertical point source, and an NBS conical transducer used to record the surface response. The received signals were then processed by the layer-stripping technique to reconstruct the layer properties and thickness from the top layer down. The recovered parameters agree well with the true parameters of the specimen. (Authors) 956101 Contact problem for saturated poroelastic solid Z. Q. Yue & A. P. S. Selvadurai, Journal of Engineering Mechanics - ASCE, 121(4), 1995, pp 502-512. The paper analytically examines the axisymmetric ainteraction between a rigid, circular, flat indentor and a poroelastic half-space that is saturated with a compressible fluid. The drainage conditions at the surface of the poroelastic halfspace are considered as either completely drained, or partially drained, or completely undrained. By using the integral transform techniques, the paper develops the governing coupled integral equations. Efficient computational algorithms are proposed to evaluate the timedependent behavior of the rigid, circular indentor. The numerical results presented in the paper illustrate the manner in which the three variations in pore-pressure boundary conditions and the undrained compressibility of pore-fluid influence the consolidation response of the indentor. (from Authors) 956102 SPTF: 2. parte (SPTF: 2nd part) S. M. T. Ranxini, Solose Rochas, 17(3), 1994, pp 189-190. This paper recommends using torque measurements in conjunction with standard penetration tests (SPT) to: 1) determine the value of the friction between the sampler and the soil and 2) act as a control for the value of the SPT itself. (from English summary) 956103 Neural networks for evaluating CPT calibration chamber test data A. T. C. Goh, Microcomputers in Civil Engineering, 10(2), 1995, pp 147-151. The feasibility of using neural network models for evaluating CPT calibration chamber test data is investigated. The backpropagation neural network algorithm was used to analyze the data. After learning from a set of randomly selected patterns, the neural network model was able to produce reasonably accurate predictions for patterns not included in the training set. The neural network performance was found to be simpler and more effective than regression analysis for modeling the CPT test data. Correlations between the cone measurements and the engineering properties of sand can be developed using the generalization capabilities of the neural network. (Author)
h STRENGTH
956104 Compressive strength for an aggregated and partially saturated soil M. A. Nearing, Soil Science Society of America Journal, 59(l), 1995, pp 35-38. Soil strength increases with the application of soil water suctions, which impart an increasing level of effective confining stress on the soil mass. The relationship between effective confining stress and suction is influenced by soil water content. For sands, effective confming stress is approximated by the multiple of soil water suction and total saturation of the soil pores. For aggregated soils this is not true. This study was undertaken to test the hypothesis that the saturation of interaggregate pores in aggregated soils controls the level of effective stress and, subsequently, soil strength relationships. Unconfined compressive strength and triaxial compression strength were measured. Results indicated that axial stress at failure for the soil was linearly related to the product of soil water suction and the saturation level of the interaggregate soil pores. Also, the slope of the regression line was statistically equivalent to the slope of the line relating axial failure stress and effective confining stresses in the saturated triaxial tests. (Author) 956105 Constitutive modelling and instabllltles of soil behaviour F. Darve, E. Flavigny & M. Meghachou, Computers & Geotechnics, 17(2), 1995, pp 203-224. By utilising an incrementally non-linear model and various types of loading paths, (i.e. proportional loading and with multiple bends) stability and uniqueness are more precisely investigated in the case of undrained paths on loose sands. The theoretical results are also analysed with respect to the convergency of the response curyes when the length of bends decreases. It is then shown that some conclusions obtained in the case of undrained loading can be general&d for a large class of stress paths. (Authors) 956106 Modified uedometer for arid, saline soils 0. S. B. Al-Amoudi & S. N. Abduljauwad, Journal of Geotechnical Engineering - ASCE, 120(10), 1994, pp 18921897. Recent work conducted on a sabkha indicated that the conventional oedometer apparatus was incapable of detecting the collapse potential. This study proposes a modification to the conventional oedometer to allow the water to percolate through the soil sample under a constant head. Tests indicate that sabkhas have a collapse potential that can be classified as trouble. This collapse is primarily ascribable to the dissolution of NaCl leaching of calcium and soil grain adjustment. (from Authors) 956197 Particle orientation and velocity equations of clay in a plane-strain condition M. Djavid, Transactions - ASME: Journal of Applied Mechanics, 62(l), 1995, pp 126-130. The directional property of soils, particularly clays, are directly related to the particle orientations. The platy clay particles do possess the tendency to reorient themselves in the most stable condition against applied stress. In this study an angle 8, which is the preferred (therefore stable) orientation of clay particles, is introduced. Using this concept and slip-line theory, the velocity equations of clay in a plane-strain condition are developed. Any change in clay particle orientation is essentially dependent on principal stresses magnitudes as well as their directions. Therefore, the effect of rotation of principal stresses can be included and quantified. (Author)
PROPERTIESDEFORMATION
Deformation and strength characteristics 956100 Inversion of the elastic parameters of a layered medium Pei-Ling Liu, Chong-Dao Tsai & Tsung-Tsong Wu, Journal - Acoustical Society of America, 97(3), 1995, pp 1687-1693. This paper presents a method for constructing the elastic parameters of a layered elastic medium such as the wave velocities, densities, and thicknesses of the layers. The inverse problem is formulated as optimization problem in which the norm of the discrepancies between the measured and calculated surface response is minimized. The experiments were conducted on a thin plate. The impact of a steel ball was adopted to generate a vertical point source, and an NBS conical transducer used to record the surface response. The received signals were then processed by the layer-stripping technique to reconstruct the layer properties and thickness from the top layer down. The recovered parameters agree well with the true parameters of the specimen. (Authors) 956101 Contact problem for saturated poroelastic solid Z. Q. Yue & A. P. S. Selvadurai, Journal of Engineering Mechanics - ASCE, 121(4), 1995, pp 502-512. The paper analytically examines the axisymmetric ainteraction between a rigid, circular, flat indentor and a poroelastic half-space that is saturated with a compressible fluid. The drainage conditions at the surface of the poroelastic halfspace are considered as either completely drained, or partially drained, or completely undrained. By using the integral transform techniques, the paper develops the governing coupled integral equations. Efficient computational algorithms are proposed to evaluate the timedependent behavior of the rigid, circular indentor. The numerical results presented in the paper illustrate the manner in which the three variations in pore-pressure boundary conditions and the undrained compressibility of pore-fluid influence the consolidation response of the indentor. (from Authors) 956102 SPTF: 2. parte (SPTF: 2nd part) S. M. T. Ranxini, Solose Rochas, 17(3), 1994, pp 189-190. This paper recommends using torque measurements in conjunction with standard penetration tests (SPT) to: 1) determine the value of the friction between the sampler and the soil and 2) act as a control for the value of the SPT itself. (from English summary) 956103 Neural networks for evaluating CPT calibration chamber test data A. T. C. Goh, Microcomputers in Civil Engineering, 10(2), 1995, pp 147-151. The feasibility of using neural network models for evaluating CPT calibration chamber test data is investigated. The backpropagation neural network algorithm was used to analyze the data. After learning from a set of randomly selected patterns, the neural network model was able to produce reasonably accurate predictions for patterns not included in the training set. The neural network performance was found to be simpler and more effective than regression analysis for modeling the CPT test data. Correlations between the cone measurements and the engineering properties of sand can be developed using the generalization capabilities of the neural network. (Author)
h STRENGTH
956104 Compressive strength for an aggregated and partially saturated soil M. A. Nearing, Soil Science Society of America Journal, 59(l), 1995, pp 35-38. Soil strength increases with the application of soil water suctions, which impart an increasing level of effective confining stress on the soil mass. The relationship between effective confining stress and suction is influenced by soil water content. For sands, effective confming stress is approximated by the multiple of soil water suction and total saturation of the soil pores. For aggregated soils this is not true. This study was undertaken to test the hypothesis that the saturation of interaggregate pores in aggregated soils controls the level of effective stress and, subsequently, soil strength relationships. Unconfined compressive strength and triaxial compression strength were measured. Results indicated that axial stress at failure for the soil was linearly related to the product of soil water suction and the saturation level of the interaggregate soil pores. Also, the slope of the regression line was statistically equivalent to the slope of the line relating axial failure stress and effective confining stresses in the saturated triaxial tests. (Author) 956105 Constitutive modelling and instabllltles of soil behaviour F. Darve, E. Flavigny & M. Meghachou, Computers & Geotechnics, 17(2), 1995, pp 203-224. By utilising an incrementally non-linear model and various types of loading paths, (i.e. proportional loading and with multiple bends) stability and uniqueness are more precisely investigated in the case of undrained paths on loose sands. The theoretical results are also analysed with respect to the convergency of the response curyes when the length of bends decreases. It is then shown that some conclusions obtained in the case of undrained loading can be general&d for a large class of stress paths. (Authors) 956106 Modified uedometer for arid, saline soils 0. S. B. Al-Amoudi & S. N. Abduljauwad, Journal of Geotechnical Engineering - ASCE, 120(10), 1994, pp 18921897. Recent work conducted on a sabkha indicated that the conventional oedometer apparatus was incapable of detecting the collapse potential. This study proposes a modification to the conventional oedometer to allow the water to percolate through the soil sample under a constant head. Tests indicate that sabkhas have a collapse potential that can be classified as trouble. This collapse is primarily ascribable to the dissolution of NaCl leaching of calcium and soil grain adjustment. (from Authors) 956197 Particle orientation and velocity equations of clay in a plane-strain condition M. Djavid, Transactions - ASME: Journal of Applied Mechanics, 62(l), 1995, pp 126-130. The directional property of soils, particularly clays, are directly related to the particle orientations. The platy clay particles do possess the tendency to reorient themselves in the most stable condition against applied stress. In this study an angle 8, which is the preferred (therefore stable) orientation of clay particles, is introduced. Using this concept and slip-line theory, the velocity equations of clay in a plane-strain condition are developed. Any change in clay particle orientation is essentially dependent on principal stresses magnitudes as well as their directions. Therefore, the effect of rotation of principal stresses can be included and quantified. (Author)