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Determination of shear strength of soil under dynamic loading
230A 924196 Exact results for generalised Gassmann's equations in composite porous media with two constituents Berryman, J G; Milton, G W Geophysics V56, NI2, Dec 1991, P1950-1960 Biot first derived equations for elastic wave propagation through fluid filled porous media. Gassmann showed how the coefficients of Biot theory depend on the compressibility of the pore fluid, but this analysis is only rigorously applicable if the solid matrix has only one constituent. Gassmann's equations have been generalised and exact formulae derived for two parameters required to describe wave propagation in a two component conglomerate. Effective constants are estimated in terms of drained frame modulus and constituent moduli.
924197 Evolution of porosity and seismic structure of upper oceanic crust: importance of aspect ratios Wilkens, R H; Fryer, G J; Karsten, J J Geophys Res V96, NBII, Oct 1991, P17981-17995 Seismic properties of the uppermost igneous crust are dominated by porosity effects, initially determined by the physics of extrusion but soon modified by alteration and hydrothermal deposition. P wave velocity-porosity behaviour of basalts has been examined on the laboratory scale and at the outcrop scale using well log data. Extrapolation to seismic scale requires application of rock physics theory. Two simple models of the oceanic crust are proposed which differ in level of void filling by alteration products and amount of crack (high aspect ratio) porosity. Computed P wave velocity and porosity profiles are consistent with well log and seismic data.
924198 Elastic wave scattering by anisotropic obstacles: application to fractured volumes Gibson, R L; Ben-Menahem, A J Geophys Res V96, NBI2, Nov 1991, P19905-19924 The effect of a small volume of fracturing within a homogeneous background medium on scattering of elastic waves is analysed. Radiation patterns are evaluated for the cases of random fracture patterns or aligned arrays with equal fracture density. Scattering from the parallel crack volume is larger than from the random array in some directions, smaller in others. Some hypothetical seismic experiments are described which can use these results to predict whether a fractured volume contains aligned or random cracks.
924200 Velocity and density structure of the 4000m cntstal segment at the KTB drilling site and their relationship to lithological and microstructural characteristics of the rocks: an experimental approach Kern, H; Schmidt, R; Popp, T Sci Drilling V2, N2-3, 1991, P130-145 P and S wave velocities and their directional dependence, crack porosities, and density were measured on representative KTB core samples at confining pressure up to 600MPa and temperatures 20-600 deg C. Velocity anisotropy resulting from oriented microcracks and crystallographic textures was evident in all cases. Seismic anisotropy was most easily detected via shear wave splitting. A model of velocity and density structure over the 3-4km profile is developed and compared to logging data. Microfracturing has significant influence on wave velocities, especially in the uppermost 2km.
924201 Deformability of water-saturated sands under cyclic loads Zaretskii, Y K; Vorontsov, E I; Baizakov, A A Soil Mech Found Engng V28, N1, Jan-Feb 1991, P31-35 Laboratory triaxial tests on saturated fine sand are reported. Static drained tests were followed by cyclic loading at a frequency of 5Hz. Failure was achieved by increasing the amplitude of the cyclic load or gradual increase of static deviatoric load at constant cyclic load amplitude. Volume strain, development of plastic strain, and pore pressures were monitored. Results may be used to assess stability of sand deposits to seismic excitation.
924202 Complete seismic properties obtained from microcrack fabrics and textures in an amphibolite from the Ivrea zone, Western Alps, Italy Siegesmund, S; Vollbrecht, A Tectonophysics V199, NI, Dec 1991, P13-24 P wave velocities and shear wave splitting were measured for an amphibolite at pressures to 800MPa. Elastic properties and seismic anisotropies for the rock were also calculated on the basis of the texture of the major minerals and their respective elastic constants. Where the effects of microcracks are eliminated (above 200-300MPa) measured and calculated values agree well. Microcracks have greatest effects at low confining pressures. The crack fabric is characterised by oriented transgranular and cleavage cracks. Bulk anisotropy at low pressure, computed by superimposing texture and crack-induced anisotropies, is consistent with measured values.
924199 Determination of shear strength of soil under dynamic loading Kokhanenko, I K; Maklakov, S F; Prischepa, V A Mech Solids 1/25, N4, 1990, P192-194
924203 Fatigue behaviour of granite under cyclic loading Ishizuka, Y; Abe, T; Kodama, J Proc ISRM International Symposium on Static and Dynamic Considerations in Rock Engineering, Swaziland, 10-12 September 1990 P139-146, Publ Rotterdam: A A Balkema, 1990
A method has been developed to directly measure the tangential stresses on the surface of a body as it penetrates into a barrier. Conical or cylindrical projectiles, instrumented with piezoelectric transducers on their surfaces, are fired by an air gun into a soil body. Results show that for clay under intense dynamic loading, tangential stresses measured decrease to a negligible value, the material behaving as a compressible fluid.
Tests were carried out on 3 sets of specimens of Inada Granite in an electro-hydraulic, servo-controlled testing machine. Uniaxial compression tests were executed in wet and dry states, and triaxial tests at a range of confining pressures. Effects of strain rate on static strength, effects of frequency on fatigue, and effects of confining pressure and water on the stress-cycles to failure curve have been evaluated.
© 1992 Pergamon Press Ltd. Reproduction not permitted
924197 Evolution of porosity and seismic structure of upper oceanic crust: importance of aspect ratios Wilkens, R H; Fryer, G J; Karsten, J J Geophys Res V96, NBII, Oct 1991, P17981-17995 Seismic properties of the uppermost igneous crust are dominated by porosity effects, initially determined by the physics of extrusion but soon modified by alteration and hydrothermal deposition. P wave velocity-porosity behaviour of basalts has been examined on the laboratory scale and at the outcrop scale using well log data. Extrapolation to seismic scale requires application of rock physics theory. Two simple models of the oceanic crust are proposed which differ in level of void filling by alteration products and amount of crack (high aspect ratio) porosity. Computed P wave velocity and porosity profiles are consistent with well log and seismic data.
924198 Elastic wave scattering by anisotropic obstacles: application to fractured volumes Gibson, R L; Ben-Menahem, A J Geophys Res V96, NBI2, Nov 1991, P19905-19924 The effect of a small volume of fracturing within a homogeneous background medium on scattering of elastic waves is analysed. Radiation patterns are evaluated for the cases of random fracture patterns or aligned arrays with equal fracture density. Scattering from the parallel crack volume is larger than from the random array in some directions, smaller in others. Some hypothetical seismic experiments are described which can use these results to predict whether a fractured volume contains aligned or random cracks.
924200 Velocity and density structure of the 4000m cntstal segment at the KTB drilling site and their relationship to lithological and microstructural characteristics of the rocks: an experimental approach Kern, H; Schmidt, R; Popp, T Sci Drilling V2, N2-3, 1991, P130-145 P and S wave velocities and their directional dependence, crack porosities, and density were measured on representative KTB core samples at confining pressure up to 600MPa and temperatures 20-600 deg C. Velocity anisotropy resulting from oriented microcracks and crystallographic textures was evident in all cases. Seismic anisotropy was most easily detected via shear wave splitting. A model of velocity and density structure over the 3-4km profile is developed and compared to logging data. Microfracturing has significant influence on wave velocities, especially in the uppermost 2km.
924201 Deformability of water-saturated sands under cyclic loads Zaretskii, Y K; Vorontsov, E I; Baizakov, A A Soil Mech Found Engng V28, N1, Jan-Feb 1991, P31-35 Laboratory triaxial tests on saturated fine sand are reported. Static drained tests were followed by cyclic loading at a frequency of 5Hz. Failure was achieved by increasing the amplitude of the cyclic load or gradual increase of static deviatoric load at constant cyclic load amplitude. Volume strain, development of plastic strain, and pore pressures were monitored. Results may be used to assess stability of sand deposits to seismic excitation.
924202 Complete seismic properties obtained from microcrack fabrics and textures in an amphibolite from the Ivrea zone, Western Alps, Italy Siegesmund, S; Vollbrecht, A Tectonophysics V199, NI, Dec 1991, P13-24 P wave velocities and shear wave splitting were measured for an amphibolite at pressures to 800MPa. Elastic properties and seismic anisotropies for the rock were also calculated on the basis of the texture of the major minerals and their respective elastic constants. Where the effects of microcracks are eliminated (above 200-300MPa) measured and calculated values agree well. Microcracks have greatest effects at low confining pressures. The crack fabric is characterised by oriented transgranular and cleavage cracks. Bulk anisotropy at low pressure, computed by superimposing texture and crack-induced anisotropies, is consistent with measured values.
924199 Determination of shear strength of soil under dynamic loading Kokhanenko, I K; Maklakov, S F; Prischepa, V A Mech Solids 1/25, N4, 1990, P192-194
924203 Fatigue behaviour of granite under cyclic loading Ishizuka, Y; Abe, T; Kodama, J Proc ISRM International Symposium on Static and Dynamic Considerations in Rock Engineering, Swaziland, 10-12 September 1990 P139-146, Publ Rotterdam: A A Balkema, 1990
A method has been developed to directly measure the tangential stresses on the surface of a body as it penetrates into a barrier. Conical or cylindrical projectiles, instrumented with piezoelectric transducers on their surfaces, are fired by an air gun into a soil body. Results show that for clay under intense dynamic loading, tangential stresses measured decrease to a negligible value, the material behaving as a compressible fluid.
Tests were carried out on 3 sets of specimens of Inada Granite in an electro-hydraulic, servo-controlled testing machine. Uniaxial compression tests were executed in wet and dry states, and triaxial tests at a range of confining pressures. Effects of strain rate on static strength, effects of frequency on fatigue, and effects of confining pressure and water on the stress-cycles to failure curve have been evaluated.
© 1992 Pergamon Press Ltd. Reproduction not permitted