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Numerical modelling of a repeated fault-slip
125A 912495 Continuous gas monitoring for the assessment of outborstproneness at a mining face Beamish, B B lnt J Min Geol Engng V8, N2, June 1990, P131-147
912499 Ekofisk reservoir pressure drops and seabed subsidence Mes, M J Pro¢ 22nd Annual Offshore Technology Conference, Houston, 7-10 May, 1990 V1, P373-387. Publ Richardson: OTC, 1990
Data from three development panels at No 2 Mines, Collinsville, Queensland, are discussed. In the first panel, 2 outbursts occurred during mining under virgin conditions, a third at the edge of a gas drained block adjacent to a thrust fault. The second panel progressed successfully through the fault and was finally halted due to high gas flow rates. The third panel was through a gas drained block for which substantial reduction in gas emission was achieved. Outburst proneness could be classified and predicted on the basis of rate of face cut out cycle (FCC) carbon dioxide emission.
Subsidence of the seabed of the Ekofisk field has been monitored since early 1985, using satellites and seafloor pressure gauges. Satellite measured subsidence rates have been correlated with reservoir pressure drops to relate pressure decreases to increases in subsidence. Greatest subsidence is found in the centre of the field. It is possible to estimate short term subsidence properties from reservoir pressure drops and vice versa. Short term behaviour only is considered: computer programs have been developed for long term predictions but are not described.
912496 Land subsidence due to gas[oil production in inhomogeneous transversely anisotropic half-space by a boundary element method Sartoretto, F; Gambolati, G; Rinaldo, A lnt J Num Anal Meth Geomech VI4, N6, Aug 1990, P379399 A previously developed boundary element model of pumping induced subsidence over a homogeneous, isotropic half space, which uses Bctti's reciprocal theorem and the classical solution to the Boussinesq equation, is extended to the inhomogeneous, transversely anisotropic case with the aid of a 2D finite element model which provides a numerical solution for the actual multi-layer system of the subsurface. This coupled approach is used to simulate behaviour of the Campo Ravenna Terra gas field in Italy in the period 1950-1980. Results compare well with those of the more expensive 3D finite element approach.
912497 Development of in-situ rockburst precursor warning systems Archibald. J F; Calder, P N; Bullock, K; Madsen, D Min Sci Technol VII, N2, Sept 1990, PI29-152 Design and development of a computer based data acquisition and processing system to monitor in-mine acoustic emission and apply pattern recognition techniques to provide warnings of impending rockburst is described. The system, from Queen's University, Ontario, uses standard hardware and software components. Long term results of microseismic evaluation of 3 pillars subject to different stress systems are described. Significant differences in behaviour were seen and identified on the basis of acoustic examination. With suitable characterization/calibration of seismic signatures of rockburst, this equipment can be a useful safety monitoring tool.
912498 Comments on surface subsidence prediction Peng, S S Min Sci Teehnol VII, N2, Sept 1990, P207-211 Problems occurring during application of subsidence prediction models are discussed, considering model imperfections. error in representative parameters or coefficients, errors in subsidence surveying, and man-made errors. Methods of comparing accuracy of subsidence prediction are assessed for the Adamek and Jeran, NCB, Kratzsch, and Brauner models.
912500 Numerical modeling of rockburst Bardet, J P Proc 3rd International Symposium on Numerical Models in Geomechnnics (NUMOG I!i), Niagara Fulls, 8-11 May 1989 P311-318. Publ London: Elsevier Applied Science, 1989 Rockbursting considered as a phenomenon of surface instability was first examined by Biot 0965) who studied the elastic half space under compressive stress, the problem being similar to buckling in structural dynamics. A finite element simulation of plane strain compression of a cube is presented, with stressdisplacement response and surface instability modelled. Analytical and numerical results are compared, The numerical technique is seen to be able to detect the emergence of surface instability.
Influence of dynamic loads 912501 Numerical modelling of a repeated fault-slip Webber, S J J S Aft lnst Min Metall V90, N6, June 1990, PI33-140 A large scale seismic event (magnitude 5.2) occurring on the Vaal Reefs Mine in 1977 and a subsequent event in 1988 have been modelled using the MINSIM-D boundary element program. The first event could not be attributed purely to mininginduced stresses, and probably results from interaction between induced and large scale tectonic stresses. Stress changes occurring due to mining in the subsequent II years are considered capable of generating sufficient excess shear stress to be responsible for the second event, magnitude 4.3, the upper limit for magnitude of purely mining induced events. 912502 Temporal variations in seismicity during quasi-static and dynamic rock failure Meredith. P G; Main. I G; Jones, C Tectonophys&s VI75. NIl3, March 1990, P249-268. (Paper to the Symposium on Earthquake Source Processes, 19th IUGG General Assembly, Vancourer, 19-21 August 1987) In heterogenous materials, dynamic failure is almost always preceded by inelastic strain hardening and often by strain softening after peak stress. These phases are due to time dependent growth and coalescence of microfractures or faults, and may be followed by studying the seismic events they generate. A comprehensive model is derived to explain temporal variation of seismic b-value for several time-varying applied stress regimes under conditions of constant remote strain rate and crack growth dominated by enhanced stress corrosion. Predictions are compared to observations at laboratory scale and from recent major earthquakes.
1991 Pergamon Press plc. Reproduction not permitted
912499 Ekofisk reservoir pressure drops and seabed subsidence Mes, M J Pro¢ 22nd Annual Offshore Technology Conference, Houston, 7-10 May, 1990 V1, P373-387. Publ Richardson: OTC, 1990
Data from three development panels at No 2 Mines, Collinsville, Queensland, are discussed. In the first panel, 2 outbursts occurred during mining under virgin conditions, a third at the edge of a gas drained block adjacent to a thrust fault. The second panel progressed successfully through the fault and was finally halted due to high gas flow rates. The third panel was through a gas drained block for which substantial reduction in gas emission was achieved. Outburst proneness could be classified and predicted on the basis of rate of face cut out cycle (FCC) carbon dioxide emission.
Subsidence of the seabed of the Ekofisk field has been monitored since early 1985, using satellites and seafloor pressure gauges. Satellite measured subsidence rates have been correlated with reservoir pressure drops to relate pressure decreases to increases in subsidence. Greatest subsidence is found in the centre of the field. It is possible to estimate short term subsidence properties from reservoir pressure drops and vice versa. Short term behaviour only is considered: computer programs have been developed for long term predictions but are not described.
912496 Land subsidence due to gas[oil production in inhomogeneous transversely anisotropic half-space by a boundary element method Sartoretto, F; Gambolati, G; Rinaldo, A lnt J Num Anal Meth Geomech VI4, N6, Aug 1990, P379399 A previously developed boundary element model of pumping induced subsidence over a homogeneous, isotropic half space, which uses Bctti's reciprocal theorem and the classical solution to the Boussinesq equation, is extended to the inhomogeneous, transversely anisotropic case with the aid of a 2D finite element model which provides a numerical solution for the actual multi-layer system of the subsurface. This coupled approach is used to simulate behaviour of the Campo Ravenna Terra gas field in Italy in the period 1950-1980. Results compare well with those of the more expensive 3D finite element approach.
912497 Development of in-situ rockburst precursor warning systems Archibald. J F; Calder, P N; Bullock, K; Madsen, D Min Sci Technol VII, N2, Sept 1990, PI29-152 Design and development of a computer based data acquisition and processing system to monitor in-mine acoustic emission and apply pattern recognition techniques to provide warnings of impending rockburst is described. The system, from Queen's University, Ontario, uses standard hardware and software components. Long term results of microseismic evaluation of 3 pillars subject to different stress systems are described. Significant differences in behaviour were seen and identified on the basis of acoustic examination. With suitable characterization/calibration of seismic signatures of rockburst, this equipment can be a useful safety monitoring tool.
912498 Comments on surface subsidence prediction Peng, S S Min Sci Teehnol VII, N2, Sept 1990, P207-211 Problems occurring during application of subsidence prediction models are discussed, considering model imperfections. error in representative parameters or coefficients, errors in subsidence surveying, and man-made errors. Methods of comparing accuracy of subsidence prediction are assessed for the Adamek and Jeran, NCB, Kratzsch, and Brauner models.
912500 Numerical modeling of rockburst Bardet, J P Proc 3rd International Symposium on Numerical Models in Geomechnnics (NUMOG I!i), Niagara Fulls, 8-11 May 1989 P311-318. Publ London: Elsevier Applied Science, 1989 Rockbursting considered as a phenomenon of surface instability was first examined by Biot 0965) who studied the elastic half space under compressive stress, the problem being similar to buckling in structural dynamics. A finite element simulation of plane strain compression of a cube is presented, with stressdisplacement response and surface instability modelled. Analytical and numerical results are compared, The numerical technique is seen to be able to detect the emergence of surface instability.
Influence of dynamic loads 912501 Numerical modelling of a repeated fault-slip Webber, S J J S Aft lnst Min Metall V90, N6, June 1990, PI33-140 A large scale seismic event (magnitude 5.2) occurring on the Vaal Reefs Mine in 1977 and a subsequent event in 1988 have been modelled using the MINSIM-D boundary element program. The first event could not be attributed purely to mininginduced stresses, and probably results from interaction between induced and large scale tectonic stresses. Stress changes occurring due to mining in the subsequent II years are considered capable of generating sufficient excess shear stress to be responsible for the second event, magnitude 4.3, the upper limit for magnitude of purely mining induced events. 912502 Temporal variations in seismicity during quasi-static and dynamic rock failure Meredith. P G; Main. I G; Jones, C Tectonophys&s VI75. NIl3, March 1990, P249-268. (Paper to the Symposium on Earthquake Source Processes, 19th IUGG General Assembly, Vancourer, 19-21 August 1987) In heterogenous materials, dynamic failure is almost always preceded by inelastic strain hardening and often by strain softening after peak stress. These phases are due to time dependent growth and coalescence of microfractures or faults, and may be followed by studying the seismic events they generate. A comprehensive model is derived to explain temporal variation of seismic b-value for several time-varying applied stress regimes under conditions of constant remote strain rate and crack growth dominated by enhanced stress corrosion. Predictions are compared to observations at laboratory scale and from recent major earthquakes.
1991 Pergamon Press plc. Reproduction not permitted