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Microprocessor controlled pump for triaxial cell pressure control. Technical note
280A 925O54 Design and optimisation of mortars for the rehabilitation of monuments in Upper Egypt (In French) Martinet, G; Le Roux, A; Martineau, F lnt ,4ssoc Engng Geoi Bull N44, Oct 1991, P55-67
925058 Strain-softening behaviour of granular soil in strain-path testing Chu, J; Lo, S C R; Lee, I K J Geotech Engng Div ASCE VllS, N2. Feb 1992, P191-208
Restoration of the Temple of Amon at Karnak has been going on for about 100 years. No suitable mortar has yet been developed for long term repair of damaged sandstones. A variety of mortar mixes has been examined at the LCPC under conditions simulating the environment at the site, to test applicability and durability. The recommended mix developed allows the craft based approach to the restoration work to be retained.
A uniformly graded sand was tested in a deformation controlled compressive machine, with direct strain-path control achieved by controlling the ratio of axial strain increment. Strain softening, as described by Prevost and Hoeg (1975), was studied. Two types of strain softening behaviour were identified, prefailure and postfailure strain softening, and conditions for their occurrence established. The shear strength of the sample was found to be dependent on postfailure strain history.
925O55 Microprocessor controlled pump for triaxial cell pressure control. Technical note Meyers, A G; Priest, S G lnt J Rock Mech Min Sci V29, N2, March 1992, P187-191 The triaxial cell is a primary component of most rock testing laboratories. Manual control of cell pressure by hand pump and bleed-off valve presents many problems. To overcome these, a microprocessor controlled linear displacement pump has been developed. The pump and pressure control unit designs are illustrated, and specimen volume change measurement is described. The equipment is robust, reliable and simple to use.
925056 Preparation and deformation of synthetic aggregates of quartz Luan, F C; Paterson, M S J Geophys Res V97, NBI, Jan 1992, P301-320 Synthetic aggregates with a range of water contents comparable to those of previously tested natural quartzites were prepared by hydrothermal isostatic pressing of natural quartz powder, impure silica gel, and high purity silicic acid. When deformed at 1200-1300 deg K, flow stress showed an inverse relation with estimated water pressure. The specimen sets from amorphous silica, for which pore water equilibration is expected, showed activation energies about 1500 k J/mole as water pressure approached confining pressure. Stress exponents were about 2.3 and 4 for specimens from impure and pure silica, despite respective grain sizes of 90 and 20 microns. The impure specimens have higher intragranular strength but grain boundary processes contribute to their strain.
925057 Damage mechanics model for fault zone friction Steacy, S J; Sammis, C G J Geophys Res 1/97, NB1, Jan 1992, t'587-594 Shear strength of a fault is calculated using a damage mechanics model for shear failure under compressive loading. The distribution of initial damage (starter flaws) is taken to be fractal ( D = 2.6) on the basis of field studies. At low confining pressures the largest flaws dominate fracture, and the shear strength is inversely related to square root of the size of the largest flaw. At crustal confining pressure, strength becomes dependent only on density of starter flaws. Macroscopic behaviour of the fault zone becomes the same as frictional behaviour of the numerous small fractures of which it is comprised, if initial density of starter flaws is sufficiently large.
925059 Flow theory for sand during rotation of principal stress direction Gutierrez, M; Ishihara, K; Towhata, I Soils Found 1/31, N4, Dec 1991, P121-132 Laboratory tests involving rotation of principal stress direction were carried out on specimens of sand in a hollow cylinder apparatus. Strain components were measured. Nonuniqueness of dependency of direction of plastic strain increment on direction of stress increment was observed, which contradicts the so-called postulate of uniqueness of flow in plasticity theory. A plastic potential theory capable of representing the observed behaviour is developed and verified using experimental results and stress probe tests.
925060 Evolution of shear modulus and fabric during shear deformation Chen, Y C; Hung, H Y Soils Found V31, N4, Dec 1991, P148-160 The discrete element code TRUBAL was used in numerical studies of shear modulus and fabric of assemblies of spheres. Results are compared to those of physical experiments. Good qualitative and quantitative agreement for stress strain behaviour and shear modulus is observed. Induced anisotropic fabric and locked-in shear forces after a load/unload cycle reflect the previous stress history. During the next load cycle these locked-in forces will affect the shear modulus, the nature of the effect being dependent on the relative direction of initial and second shear strains.
925061 Cyclic strength of underconsolidated clay. Technical note Hirao, K; Yasuhara, K Soils Found Y31, N4, Dec 1991, P180-186 The effects of the preconsolidation period on cyclic strength of reconstituted clay have been examined. Cyclic strength is governed by an increase in effective stress developed during the process of consolidation, and is better defined by degree of consolidation in terms of effective stress than by volumetric strain. A unique relation between cyclic shear stress and number of cycles, independent of consolidation time, is obtained by using undrained static strength in place of effective stress in normalizing cyclic shear stress.
© 1992 Pergamon Press Ltd. Reproduction not permitted
925058 Strain-softening behaviour of granular soil in strain-path testing Chu, J; Lo, S C R; Lee, I K J Geotech Engng Div ASCE VllS, N2. Feb 1992, P191-208
Restoration of the Temple of Amon at Karnak has been going on for about 100 years. No suitable mortar has yet been developed for long term repair of damaged sandstones. A variety of mortar mixes has been examined at the LCPC under conditions simulating the environment at the site, to test applicability and durability. The recommended mix developed allows the craft based approach to the restoration work to be retained.
A uniformly graded sand was tested in a deformation controlled compressive machine, with direct strain-path control achieved by controlling the ratio of axial strain increment. Strain softening, as described by Prevost and Hoeg (1975), was studied. Two types of strain softening behaviour were identified, prefailure and postfailure strain softening, and conditions for their occurrence established. The shear strength of the sample was found to be dependent on postfailure strain history.
925O55 Microprocessor controlled pump for triaxial cell pressure control. Technical note Meyers, A G; Priest, S G lnt J Rock Mech Min Sci V29, N2, March 1992, P187-191 The triaxial cell is a primary component of most rock testing laboratories. Manual control of cell pressure by hand pump and bleed-off valve presents many problems. To overcome these, a microprocessor controlled linear displacement pump has been developed. The pump and pressure control unit designs are illustrated, and specimen volume change measurement is described. The equipment is robust, reliable and simple to use.
925056 Preparation and deformation of synthetic aggregates of quartz Luan, F C; Paterson, M S J Geophys Res V97, NBI, Jan 1992, P301-320 Synthetic aggregates with a range of water contents comparable to those of previously tested natural quartzites were prepared by hydrothermal isostatic pressing of natural quartz powder, impure silica gel, and high purity silicic acid. When deformed at 1200-1300 deg K, flow stress showed an inverse relation with estimated water pressure. The specimen sets from amorphous silica, for which pore water equilibration is expected, showed activation energies about 1500 k J/mole as water pressure approached confining pressure. Stress exponents were about 2.3 and 4 for specimens from impure and pure silica, despite respective grain sizes of 90 and 20 microns. The impure specimens have higher intragranular strength but grain boundary processes contribute to their strain.
925057 Damage mechanics model for fault zone friction Steacy, S J; Sammis, C G J Geophys Res 1/97, NB1, Jan 1992, t'587-594 Shear strength of a fault is calculated using a damage mechanics model for shear failure under compressive loading. The distribution of initial damage (starter flaws) is taken to be fractal ( D = 2.6) on the basis of field studies. At low confining pressures the largest flaws dominate fracture, and the shear strength is inversely related to square root of the size of the largest flaw. At crustal confining pressure, strength becomes dependent only on density of starter flaws. Macroscopic behaviour of the fault zone becomes the same as frictional behaviour of the numerous small fractures of which it is comprised, if initial density of starter flaws is sufficiently large.
925059 Flow theory for sand during rotation of principal stress direction Gutierrez, M; Ishihara, K; Towhata, I Soils Found 1/31, N4, Dec 1991, P121-132 Laboratory tests involving rotation of principal stress direction were carried out on specimens of sand in a hollow cylinder apparatus. Strain components were measured. Nonuniqueness of dependency of direction of plastic strain increment on direction of stress increment was observed, which contradicts the so-called postulate of uniqueness of flow in plasticity theory. A plastic potential theory capable of representing the observed behaviour is developed and verified using experimental results and stress probe tests.
925060 Evolution of shear modulus and fabric during shear deformation Chen, Y C; Hung, H Y Soils Found V31, N4, Dec 1991, P148-160 The discrete element code TRUBAL was used in numerical studies of shear modulus and fabric of assemblies of spheres. Results are compared to those of physical experiments. Good qualitative and quantitative agreement for stress strain behaviour and shear modulus is observed. Induced anisotropic fabric and locked-in shear forces after a load/unload cycle reflect the previous stress history. During the next load cycle these locked-in forces will affect the shear modulus, the nature of the effect being dependent on the relative direction of initial and second shear strains.
925061 Cyclic strength of underconsolidated clay. Technical note Hirao, K; Yasuhara, K Soils Found Y31, N4, Dec 1991, P180-186 The effects of the preconsolidation period on cyclic strength of reconstituted clay have been examined. Cyclic strength is governed by an increase in effective stress developed during the process of consolidation, and is better defined by degree of consolidation in terms of effective stress than by volumetric strain. A unique relation between cyclic shear stress and number of cycles, independent of consolidation time, is obtained by using undrained static strength in place of effective stress in normalizing cyclic shear stress.
© 1992 Pergamon Press Ltd. Reproduction not permitted