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Physical modelling of roof strata in potash mines of Saskatchewan
188A interaction described by Blot's coefficients, which are dependent on deviatoric stress. The theory developed is used to model stress distribution around a borehole in fluid bearing rock.
Underground excavation failure mechanisms See also." 913091. 913098, 913327
913462 Gate design key to bump control Campoli, A; Barton, T; Van Dyke, F: Gauna, M; DeMarco, M Coal V95, N9, Sept 1990, P54-58
Full extraction retreat mining results in stress concentration in nearby support pillars. Rapid and violent failure (bumps) often results under stiff roof and floor conditions at great depth. Stresses and deformations accompanying bumps were monitored at a West Virginia coal mine. Underground layout changes, with larger abutment pillars to carry the applied abutment loads and prevent ground stress reaching the longwall face, were successful in reducing face bumps, with small loss in extraction ratio. Pillars bumped when in the gob rather than in advance of the face.
913463 Deformation and fracture around cylindrical openings in rock - !. Observatio~ and analysis of deformations Ewy, R T; Cook, N G W Int J Rock Mech Min Sci V27, N5, Oct 1990, P387-407 Failure around underground openings was simulated by experiments on thick walled hollow cylinders of Berea sandstone and Indiana limestone, under plane strain loading with various stress paths, transference of external pressure to infinity, and 'freezing in' of fracture geometry using Wood's metal. Elastic and inelastic deformation are examined from experimental and theoretical viewpoints. Most elastic deformations show nonlinearity and hysteresis. Overall deformations can be explained by a radially anisotropic moduli model, which allows different moduli for different stress paths. Dilatancy and strength loss close to failure, effect of internal pressure on stability, and time dependent hole closure are analysed.
913465 Application of rock mechanics principles to alleviate a complex rock engineering problem in a coal mine - a case study Khair, A W; Lim, H U; Jung, S J Rock Alechanics Contributions and Challenges: Proc 31st US Symposium, Golden, 18-20 June 1990 P77-84. Publ Rotterdam: ,4 ,4 Balkema, 1990 Severe cutter roof problems occurred at a mine in southwestern Pennsylvania. Overburden depth is 180-240m and immediate roof highly laminated shale with weak binding. Geology. rock mechanical properties, and in situ stresses were studied. An experimental longwalt entry system was designed and implemented. Yield pillars and 2m resin grouted bolts, truss bolts, and yieldable steel legs at the cutter edge were the final remedial measures. 913466 Pillar stability in ultra-close seam mining Zhou, Y; Haycocks, C Rock Mechanics Contributions and Challenges: Proe 31st US Symposium, Golden, 18-20 June 1990 P137-144. Publ Rotterdam: A A Balkema, 1990 Ultra-close seam mining (less than 8m vertical separation) creates problems due to multiseam interactions. Unique failure mechanisms of the innerburden can affect structural behaviour of upper and lower seam pillars. Aligned and staggered pillars and arching and yield pillars have been considered for multiseam extraction. Stability analysis indicates innerburden is the predominant structural component, since its failure effectively increases pillar heights and probability of instability. Innerburden stability should be maintained as the basis of stable design. 913467 Physical modelling of roof strata in potash mines of Saskatchewan Jeremie, M L; Farah, A Proc 1st International Workshop on Scale Effects in Rock Masses, Loen, 7-8 June 1990 P231-237. Publ Rotterdam: A A Balkema. 1990 Bedded roof strata exposed by long pillar mining of the Praire evaporites can, in some cases, start to deform by bed separation, which propagates to rise deeper into the ground. Massive roof falls result, which late installation of support does not prevent. Physical modelling of both reinforced and unreinforced structures was carried out to examine their behaviour under gravitational and lateral stresses. Results indicate that stability can be achieved if support is installed in critical areas whilst initial, trouble free roof conditions still exist.
913464 Case history of inco's Copper Cliff North Mine Mormon, D M; Galbraith, J E Rock Mechanics Contributions and Challenges: Proc 31st US Symposium, Golden, 18-20 June 1990 P51-58. Publ Rotterdam: A A Balkema. 1990
913468 Application of probability methods to predict rock wedge failure in shafts Esterhuizen, G S Proc Symposiura on Rock Instability Problems in Mine Shafts, Potchefstroom,lO May 1990 P37'44. Publ Marshalltown: SANGORM. 1990
Copper Cliff North, in the Sudbury Basin, is a vertical retreat mine (VRM) operation, with principal ore zone a steeply dipping tabular orebody. Initial stope design was based on the generally accepted regional stress regime. Dramatic and persistent increase in seismicity occurred in 1986. Stress measurements were undertaken, and 2- and 3-dimensional boundary element modelling of the mine carried out to establish the cause of failure. Detailed examination indicated anomalously low confining stresses, which resulted in zones of high tensile stress, Future mining is discussed.
The stability of sidewalls in vertical and inclined shafts is partly determined by wedges of rock which form by the intersections of joints or faults in the walls of the shaft. A technique is described which allows the probability of failure and occurrence of wedges to be estimated based on joint data. A computer program is briefly described which allows one to conduct such analysis rapidly. An example is given of an application to a vertical rectangular shaft. Further development of the method to evaluate circular shafts and other mining excavations is proposed. Auth.
(/ 1991 Pergamon Press plc. Reproduction not permitted
Underground excavation failure mechanisms See also." 913091. 913098, 913327
913462 Gate design key to bump control Campoli, A; Barton, T; Van Dyke, F: Gauna, M; DeMarco, M Coal V95, N9, Sept 1990, P54-58
Full extraction retreat mining results in stress concentration in nearby support pillars. Rapid and violent failure (bumps) often results under stiff roof and floor conditions at great depth. Stresses and deformations accompanying bumps were monitored at a West Virginia coal mine. Underground layout changes, with larger abutment pillars to carry the applied abutment loads and prevent ground stress reaching the longwall face, were successful in reducing face bumps, with small loss in extraction ratio. Pillars bumped when in the gob rather than in advance of the face.
913463 Deformation and fracture around cylindrical openings in rock - !. Observatio~ and analysis of deformations Ewy, R T; Cook, N G W Int J Rock Mech Min Sci V27, N5, Oct 1990, P387-407 Failure around underground openings was simulated by experiments on thick walled hollow cylinders of Berea sandstone and Indiana limestone, under plane strain loading with various stress paths, transference of external pressure to infinity, and 'freezing in' of fracture geometry using Wood's metal. Elastic and inelastic deformation are examined from experimental and theoretical viewpoints. Most elastic deformations show nonlinearity and hysteresis. Overall deformations can be explained by a radially anisotropic moduli model, which allows different moduli for different stress paths. Dilatancy and strength loss close to failure, effect of internal pressure on stability, and time dependent hole closure are analysed.
913465 Application of rock mechanics principles to alleviate a complex rock engineering problem in a coal mine - a case study Khair, A W; Lim, H U; Jung, S J Rock Alechanics Contributions and Challenges: Proc 31st US Symposium, Golden, 18-20 June 1990 P77-84. Publ Rotterdam: ,4 ,4 Balkema, 1990 Severe cutter roof problems occurred at a mine in southwestern Pennsylvania. Overburden depth is 180-240m and immediate roof highly laminated shale with weak binding. Geology. rock mechanical properties, and in situ stresses were studied. An experimental longwalt entry system was designed and implemented. Yield pillars and 2m resin grouted bolts, truss bolts, and yieldable steel legs at the cutter edge were the final remedial measures. 913466 Pillar stability in ultra-close seam mining Zhou, Y; Haycocks, C Rock Mechanics Contributions and Challenges: Proe 31st US Symposium, Golden, 18-20 June 1990 P137-144. Publ Rotterdam: A A Balkema, 1990 Ultra-close seam mining (less than 8m vertical separation) creates problems due to multiseam interactions. Unique failure mechanisms of the innerburden can affect structural behaviour of upper and lower seam pillars. Aligned and staggered pillars and arching and yield pillars have been considered for multiseam extraction. Stability analysis indicates innerburden is the predominant structural component, since its failure effectively increases pillar heights and probability of instability. Innerburden stability should be maintained as the basis of stable design. 913467 Physical modelling of roof strata in potash mines of Saskatchewan Jeremie, M L; Farah, A Proc 1st International Workshop on Scale Effects in Rock Masses, Loen, 7-8 June 1990 P231-237. Publ Rotterdam: A A Balkema. 1990 Bedded roof strata exposed by long pillar mining of the Praire evaporites can, in some cases, start to deform by bed separation, which propagates to rise deeper into the ground. Massive roof falls result, which late installation of support does not prevent. Physical modelling of both reinforced and unreinforced structures was carried out to examine their behaviour under gravitational and lateral stresses. Results indicate that stability can be achieved if support is installed in critical areas whilst initial, trouble free roof conditions still exist.
913464 Case history of inco's Copper Cliff North Mine Mormon, D M; Galbraith, J E Rock Mechanics Contributions and Challenges: Proc 31st US Symposium, Golden, 18-20 June 1990 P51-58. Publ Rotterdam: A A Balkema. 1990
913468 Application of probability methods to predict rock wedge failure in shafts Esterhuizen, G S Proc Symposiura on Rock Instability Problems in Mine Shafts, Potchefstroom,lO May 1990 P37'44. Publ Marshalltown: SANGORM. 1990
Copper Cliff North, in the Sudbury Basin, is a vertical retreat mine (VRM) operation, with principal ore zone a steeply dipping tabular orebody. Initial stope design was based on the generally accepted regional stress regime. Dramatic and persistent increase in seismicity occurred in 1986. Stress measurements were undertaken, and 2- and 3-dimensional boundary element modelling of the mine carried out to establish the cause of failure. Detailed examination indicated anomalously low confining stresses, which resulted in zones of high tensile stress, Future mining is discussed.
The stability of sidewalls in vertical and inclined shafts is partly determined by wedges of rock which form by the intersections of joints or faults in the walls of the shaft. A technique is described which allows the probability of failure and occurrence of wedges to be estimated based on joint data. A computer program is briefly described which allows one to conduct such analysis rapidly. An example is given of an application to a vertical rectangular shaft. Further development of the method to evaluate circular shafts and other mining excavations is proposed. Auth.
(/ 1991 Pergamon Press plc. Reproduction not permitted