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Undrained response of granular soil involving localized deformation
204A
PROPERTIES:FRACTURE PROCESSES
A programme of experimental studies on reworked clay samples compacted under various load pressures in oedometric conditions has been set up. The evolution of samples under compaction was followed with microscopic and macroscopic measurements. In a first step, kaolinite was chosen because it retains a high permeability which allows compaction tests to be performed within a few days. It was found that each particle is composed of several crystal units, each unit formed by -~25 individual kaolinite layers. During compaction, these particles remain undeformed, but are rotated. The angular distribution of grain orientation is a function of the applied effective stress. This reorientation is in agreement with the observed decrease in porosity and pore size. It also explains the occurrence of a strong anisotropy in the thermal conductivity and hydraulic permeability. (from Authors) 965097 Long-term strength and viscoplasticity of clayey soils Yu. K. Zaretskii, Soil Mechanics & Foundation Engineering, 32(2), 1995, pp 37-42; translated from: Osnovaniya, Fundamenty i Mekhanika Gruntov, 2, 1995, pp 2-6. During viscoplastic deformations of soils over time the strain rate is proportional to the 'overstress' with respect to the stabilized-state diagram. The stabilized-state diagram is to be determined experimentally, using the relaxation method under kinematic shear. The generalizing expression for determination of the ultimate long-term strength, is given on the basis of examination of the development kinetics of structural defects. (from Journal translation) 965098 Determination of the strength and deformation characteristics of clayey soils by shear tests in a kinematic regime Yu. K. Zaretskii & B. D. Chumichev, Soil Mechanics & Foundation Engineering, 32(2), 1995, pp 43-46; translated from: Osnovaniya, Fundamenty i Methanika Gruntov, 2, 1995, pp 7-10. The experimental investigations indicate that when 7<_ 7", the rheologlcal curves are similar for both different normal pressures, and also different strains. In first approximation, the coefficient of viscosity can be considered constant for this region of deformation. For deformations exceeding the critical, failure processes begin to prevail in the soils; this is reflected on the diagrams by an increase in the steepness of the theological curves, i.e., by a decrease in the coefficient of viscosity, which tends to zero within the limit. (from Journal translation) 965O99 Lightly cemented sand in tension and compression B. M. Das & R. N. Dass, Geotechnical & Geological Engineering, 13(3), 1995, pp 169-177. The tests were conducted with the specimens under compression and tension without any confining pressure. The cement content was varied from 4% to 8%. Based on the test results, the variations of the stress and strain ratios at failure with cement content are presented for specimens under compression and tension. (from Authors) 965100 Undrained response of granular soil involving localized deformation S. Pietruszczak, Journal of Engineering Mechanics - ASCE, 121(12), 1995, pp 1292-1297. An attempt is made to provide a macroscopic description of undrained deformation, in saturated granular materials, in the presence of a shear band. First, the case when both constituents respond in an undrained manner is considered. Subsequently, the problem is reformulated by allowing for an exchange of water in constituents due to a rapid dissipation of the excess pore pressure gradient. The formulation is applied to analyze the plane strain undrained deformation of a dense sand. The classical bifurcation analysis is used to predict the
onset of localized deformation. Results are compared with available experimental data. (from Author) 965101 Shear hand formation in sand aecording to non-coaxial plasticity model E. Papamichos & I. Vardoulakis, Geotechnique, 45(4), 1995, pp 649-661. A consistent non-coaxial plasticity theory is used. The theoretical predictions for shear band orientation and its onset are shown to agree well with experimental observations of biaxial tests. The decrease of shear band inclination angle with respect to the minor principal stress direction with increasing confining pressure supports the hypothesis of the dependency of non-coaxiality on confining pressure. (from Authors) 965102 Effect of aging on the penetration resistance of sands R. C. Joshi, G. Achari, S. R. Kaniraj & H. Wijeweera, Canadian Geotechnical Journal, 32(5), 1995, pp 767-782. The results indicate that aging significantly increases the penetration resistance of sands. The rate of increase in penetration resistance was higher for the submerged sand as compared with the dry sand. The increase in penetration resistance of the sand in a dry state was attributed to rearrangement of sand grains.In the submerged state,besides the rearrangement of sand particles, partial cementation caused by precipitation of salts and probably also silica on the sand grains and in the pores resulted in the larger increase in the penetration resistance. (from Authors) 965103 Residual strength and large-deformation potential of loose silty sands M. H. Baziar & R. Dobry, Journal of Geotechnical Engineering - ASCE, 121(12), 1995, pp 896-906. Laboratory and field evidence on residual shear strength, density, and penetration resistance of very loose, waterdeposited silty sands and sandy silts capable of liquefying and developing large shear deformations in summarized. (Authors)
Fracture processes 965104 Fracture mechanics of rocks K. Kusunose, Journal of Physics of the Earth, 43(4), 1995, pp 479-504. This paper reviews recent studies on: I) AE (acoustic emission) and cracking models, 2) failure processes and 3) frictional sliding processes, mainly based on work carried out in Japan. (from Author) 965105 Fracture growth - I. Formulation and implementations K. Wei & J.-CI. De Bremaecker, Geophysical Journal International, 122(3), 1995, pp 735-745. The orientation of fracture growth 0 can be determined by using the maximum strain-energy release-rate criterion Gm~. When a fracture is under compression, the evaluation of G(0) involves the solution to frictional contact problems, where the fracture faces are constrained by the non-interpenetration condition and a friction law. The paper proposes a repulsion scheme to handle these constraints on the fracture faces: the interpenetration is iteratively eliminated by adjusting the normal compressive force (repulsion), and the friction law is satisfied by modifying the friction resistance at each iteration. (from Authors) 965106 Fracture growth - If. Case studies K. Wei & J.-CI. De Bremaecker, Geophysical Journal International, 122(3), 1995, pp 746-754.
PROPERTIES:FRACTURE PROCESSES
A programme of experimental studies on reworked clay samples compacted under various load pressures in oedometric conditions has been set up. The evolution of samples under compaction was followed with microscopic and macroscopic measurements. In a first step, kaolinite was chosen because it retains a high permeability which allows compaction tests to be performed within a few days. It was found that each particle is composed of several crystal units, each unit formed by -~25 individual kaolinite layers. During compaction, these particles remain undeformed, but are rotated. The angular distribution of grain orientation is a function of the applied effective stress. This reorientation is in agreement with the observed decrease in porosity and pore size. It also explains the occurrence of a strong anisotropy in the thermal conductivity and hydraulic permeability. (from Authors) 965097 Long-term strength and viscoplasticity of clayey soils Yu. K. Zaretskii, Soil Mechanics & Foundation Engineering, 32(2), 1995, pp 37-42; translated from: Osnovaniya, Fundamenty i Mekhanika Gruntov, 2, 1995, pp 2-6. During viscoplastic deformations of soils over time the strain rate is proportional to the 'overstress' with respect to the stabilized-state diagram. The stabilized-state diagram is to be determined experimentally, using the relaxation method under kinematic shear. The generalizing expression for determination of the ultimate long-term strength, is given on the basis of examination of the development kinetics of structural defects. (from Journal translation) 965098 Determination of the strength and deformation characteristics of clayey soils by shear tests in a kinematic regime Yu. K. Zaretskii & B. D. Chumichev, Soil Mechanics & Foundation Engineering, 32(2), 1995, pp 43-46; translated from: Osnovaniya, Fundamenty i Methanika Gruntov, 2, 1995, pp 7-10. The experimental investigations indicate that when 7<_ 7", the rheologlcal curves are similar for both different normal pressures, and also different strains. In first approximation, the coefficient of viscosity can be considered constant for this region of deformation. For deformations exceeding the critical, failure processes begin to prevail in the soils; this is reflected on the diagrams by an increase in the steepness of the theological curves, i.e., by a decrease in the coefficient of viscosity, which tends to zero within the limit. (from Journal translation) 965O99 Lightly cemented sand in tension and compression B. M. Das & R. N. Dass, Geotechnical & Geological Engineering, 13(3), 1995, pp 169-177. The tests were conducted with the specimens under compression and tension without any confining pressure. The cement content was varied from 4% to 8%. Based on the test results, the variations of the stress and strain ratios at failure with cement content are presented for specimens under compression and tension. (from Authors) 965100 Undrained response of granular soil involving localized deformation S. Pietruszczak, Journal of Engineering Mechanics - ASCE, 121(12), 1995, pp 1292-1297. An attempt is made to provide a macroscopic description of undrained deformation, in saturated granular materials, in the presence of a shear band. First, the case when both constituents respond in an undrained manner is considered. Subsequently, the problem is reformulated by allowing for an exchange of water in constituents due to a rapid dissipation of the excess pore pressure gradient. The formulation is applied to analyze the plane strain undrained deformation of a dense sand. The classical bifurcation analysis is used to predict the
onset of localized deformation. Results are compared with available experimental data. (from Author) 965101 Shear hand formation in sand aecording to non-coaxial plasticity model E. Papamichos & I. Vardoulakis, Geotechnique, 45(4), 1995, pp 649-661. A consistent non-coaxial plasticity theory is used. The theoretical predictions for shear band orientation and its onset are shown to agree well with experimental observations of biaxial tests. The decrease of shear band inclination angle with respect to the minor principal stress direction with increasing confining pressure supports the hypothesis of the dependency of non-coaxiality on confining pressure. (from Authors) 965102 Effect of aging on the penetration resistance of sands R. C. Joshi, G. Achari, S. R. Kaniraj & H. Wijeweera, Canadian Geotechnical Journal, 32(5), 1995, pp 767-782. The results indicate that aging significantly increases the penetration resistance of sands. The rate of increase in penetration resistance was higher for the submerged sand as compared with the dry sand. The increase in penetration resistance of the sand in a dry state was attributed to rearrangement of sand grains.In the submerged state,besides the rearrangement of sand particles, partial cementation caused by precipitation of salts and probably also silica on the sand grains and in the pores resulted in the larger increase in the penetration resistance. (from Authors) 965103 Residual strength and large-deformation potential of loose silty sands M. H. Baziar & R. Dobry, Journal of Geotechnical Engineering - ASCE, 121(12), 1995, pp 896-906. Laboratory and field evidence on residual shear strength, density, and penetration resistance of very loose, waterdeposited silty sands and sandy silts capable of liquefying and developing large shear deformations in summarized. (Authors)
Fracture processes 965104 Fracture mechanics of rocks K. Kusunose, Journal of Physics of the Earth, 43(4), 1995, pp 479-504. This paper reviews recent studies on: I) AE (acoustic emission) and cracking models, 2) failure processes and 3) frictional sliding processes, mainly based on work carried out in Japan. (from Author) 965105 Fracture growth - I. Formulation and implementations K. Wei & J.-CI. De Bremaecker, Geophysical Journal International, 122(3), 1995, pp 735-745. The orientation of fracture growth 0 can be determined by using the maximum strain-energy release-rate criterion Gm~. When a fracture is under compression, the evaluation of G(0) involves the solution to frictional contact problems, where the fracture faces are constrained by the non-interpenetration condition and a friction law. The paper proposes a repulsion scheme to handle these constraints on the fracture faces: the interpenetration is iteratively eliminated by adjusting the normal compressive force (repulsion), and the friction law is satisfied by modifying the friction resistance at each iteration. (from Authors) 965106 Fracture growth - If. Case studies K. Wei & J.-CI. De Bremaecker, Geophysical Journal International, 122(3), 1995, pp 746-754.