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Influence of parallel and cross joints on shear behaviour of rock discontinuities
7A 911O46 Role of ter-~don in failure of jointed reck Handanyan, J M; Danek, E R; D'Andrea, R A; Sage, J D Proc International Symposium on Rock Joints, Loen, 4-6 June 1990 P195-202. Publ Rotterdam: A A Baikema, 1990 Difficulties in predicting large scale load deformation response of joints from laboratory scale tests are examined. Prediction methods assuming shear is the dominant mode of failure are noted. It is suggested that under certain conditions of joint spacing and asperity geometry, tensile strength of the asperities may govern joint response in non-dilational shear. Direct shear test data from specimens prepared in a gypsum based model material (DieKecn) are presented to support this hypothesis. Further confirmation is found from tests on natural marble and from finite element analyses. 911047 Normal joint stiffness as a function of spatial geometry and surface roughness Hopkins, D L; Cook, N G W; Myer, L R Proc International Symposium on Rock Joints, Locn, 4-6 June 1990 P203-210. Publ Rotterdam: A A Balkema. 1990 Normal joint stiffness as a function of void and contact geometry has been analysed using a model based on the minimization of strain energy. It is assumed that joints can be modelled as variable height asperities between semi-infinite half-spaces. In addition to the deformation of the asperities, the model accounts for deformation of the half-spaces and mechanical interaction between asperities. It is shown that normal joint stiffness is not uniquely determined by contact area. Other important parameters include the dimension and spatial geometry of the asperities and the distribution of their heights. Auth. 911048 Study on the shear strength of rock joint of partial continuity Hung, J J; Lee, T T Proc International Symposium on Rock Joints, Loan, 4-6 June 1990 P219-225. Publ Rotterdam: A A Balkema, 1990 A mathematical model based on a LEFM approach is derived for a partially continuous joint consisting of a mesoscopic crack and an intact material which is linear elastic and nonporous. Influence of porosity of real rocks and of microcracks formed ahead of the mesocrack during shear are then incorporated. Model predictions are compared to results of extensive laboratory direct shear testing of partially continuous joints in sandstone and plaster. Results from the improved model presented are more consistent with measured data than others in the literature. 911049 Laboratory simulation of joints and their influence on rock mass behaviour Indraratna, B Proc International Symposium on Rock Joints, Locn, 4-6 June 1990 P235-242. Publ Rotterdam: A A Balkema, 1990 i
Laboratory simulation of joints was achieved using a pair of hardened plaster surfaces. Shear behaviour of the simulated joint was characterised. The influence of joints on the behaviour of soft synthetic rock was studied using specimens prepared by casting plaster over networks of the simulated joints. Triaxiai tests were carried out on prismatic samples. Simulation of a tunnel opening in jointed rock was also carried out,
with tunnel wall failure mechanisms being studied. The conditions u n d e r which continuum models may be applied to jointed rocks are examined. 911050 Influence of parallel and cross joints on shear behaviour of rock discontinuities Kutter, K H; Otto, F Proc International Symposium on Rock Joints, Locn, 4-6 June 1990 P243-250. Publ Rotterdam: A A Balkema, 1990 Tests were carried out using natural joints of splits along planes of schistosity or saw cut cross joints in gneiss, or joints cast into rubber moulds using hydrostone or hydrostone/limestone materials. Influence of block size, kinematic, and geometric boundary conditions on the behaviour of joints was examined for single joints and parallel joints with or without cross joints. The effective dilation angle of the joint was the most important parameter influencing joint behaviour. Laboratory data can be applied for design purposes if size effect, normal stress, and surface interlocking are taken into account. 911051 Characteristics of acoustic emissions during shearing of rock joints Li, C; Nordlund, E Proc International Symposium on Rock Joints, Locn, 4-6 June 1990 P251-258. Publ Rotterdam: A A Balkema, 1990 Artificial and natural joints in granite and slate were sheared with AE being monitored. AE rate peaks coincided with stress associated with fracturing of asperities during joint shear. As surfaces became smooth and strength tended towards residual, shear stress drops became less frequent and larger, and AE count declined. Both roughness and compressive strength of joint surface influence AE intensity. 911052 Behaviour of rock joints and rock bridges in shear testing Li, C; Stephansson, O; Savilahti, T Proc International Symposium on Rock Joints, Loeu, 4-6 June 1990 P259-266. Publ Rotterdam: A A Balkema. 1990 Jointed core specimens of magnetite ore were tested in shear to examine the behaviour of rock joints and rock bridges. Specit mens were loaded in a special shear jig at a fixed orientation to the forced shearing plane. Failure surfaces were ragged, following pre-existing joints and traversing rock bridges en echelon. A model for rock bridge tensile failure and post failure behaviour is proposed which is supported by experimental results and acoustic emission monitored during testing. 911053 Automatic bock-pressure saturation device for triaxial testing Brandon, T L; Duncan, J M; Cadden, A W Geotech Test J V13. N2, June 1990, P77-82 Over-rapid application of back pressure to unsaturated triaxial specimens may result in inadvertent overconsolidation, which affects test results. To prevent this, an automated device has been developed, which continuously monitors maximum effective stress in the specimen and optimizes rates for increase of back and cell pressures without exceeding an allowable effective stress. Its application to tests on three soils of different grain size and saturation levels, a residual silt, a silty sand,and a clayey sand, is described.
© 1991 Pergamon Press pie. Reproduction not permitted
Laboratory simulation of joints was achieved using a pair of hardened plaster surfaces. Shear behaviour of the simulated joint was characterised. The influence of joints on the behaviour of soft synthetic rock was studied using specimens prepared by casting plaster over networks of the simulated joints. Triaxiai tests were carried out on prismatic samples. Simulation of a tunnel opening in jointed rock was also carried out,
with tunnel wall failure mechanisms being studied. The conditions u n d e r which continuum models may be applied to jointed rocks are examined. 911050 Influence of parallel and cross joints on shear behaviour of rock discontinuities Kutter, K H; Otto, F Proc International Symposium on Rock Joints, Locn, 4-6 June 1990 P243-250. Publ Rotterdam: A A Balkema, 1990 Tests were carried out using natural joints of splits along planes of schistosity or saw cut cross joints in gneiss, or joints cast into rubber moulds using hydrostone or hydrostone/limestone materials. Influence of block size, kinematic, and geometric boundary conditions on the behaviour of joints was examined for single joints and parallel joints with or without cross joints. The effective dilation angle of the joint was the most important parameter influencing joint behaviour. Laboratory data can be applied for design purposes if size effect, normal stress, and surface interlocking are taken into account. 911051 Characteristics of acoustic emissions during shearing of rock joints Li, C; Nordlund, E Proc International Symposium on Rock Joints, Locn, 4-6 June 1990 P251-258. Publ Rotterdam: A A Balkema, 1990 Artificial and natural joints in granite and slate were sheared with AE being monitored. AE rate peaks coincided with stress associated with fracturing of asperities during joint shear. As surfaces became smooth and strength tended towards residual, shear stress drops became less frequent and larger, and AE count declined. Both roughness and compressive strength of joint surface influence AE intensity. 911052 Behaviour of rock joints and rock bridges in shear testing Li, C; Stephansson, O; Savilahti, T Proc International Symposium on Rock Joints, Loeu, 4-6 June 1990 P259-266. Publ Rotterdam: A A Balkema. 1990 Jointed core specimens of magnetite ore were tested in shear to examine the behaviour of rock joints and rock bridges. Specit mens were loaded in a special shear jig at a fixed orientation to the forced shearing plane. Failure surfaces were ragged, following pre-existing joints and traversing rock bridges en echelon. A model for rock bridge tensile failure and post failure behaviour is proposed which is supported by experimental results and acoustic emission monitored during testing. 911053 Automatic bock-pressure saturation device for triaxial testing Brandon, T L; Duncan, J M; Cadden, A W Geotech Test J V13. N2, June 1990, P77-82 Over-rapid application of back pressure to unsaturated triaxial specimens may result in inadvertent overconsolidation, which affects test results. To prevent this, an automated device has been developed, which continuously monitors maximum effective stress in the specimen and optimizes rates for increase of back and cell pressures without exceeding an allowable effective stress. Its application to tests on three soils of different grain size and saturation levels, a residual silt, a silty sand,and a clayey sand, is described.
© 1991 Pergamon Press pie. Reproduction not permitted