Probabilistic techniques in roof failure prediction.
Fraher-R; Zhou-Y; Haycocks-C
Rock Mechanics: Contributions and Challenges: Proceedings of the 31st U.S. Symposium, June 18-20, 1990, Colorado School of Mines, Golden, Colorado. Hustrulid WA, Johnson GA, ed., Brookfield, VT: A.A. Balkema, 1990 Jan; :195-202
The challenge in design of room-and-pillar coal mines lies in striking an optimum balance between under- and overdesign of support structures. Ground control problems created by inadequate support can seriously reduce productivity and result in major increases in cost. A fatality caused by a roof fall costs over a million dollars (Chi and Hamilton 1987). On the other hand, using excessive support with large pillars and small openings can result in unnecessarily high mining costs. Therefore there is strong economic incentive to improve ground control practices in room-and-pillar operations. The occurrence and frequency of roof falls are related to the type of roof support, support density, geology, structural discontinuities, location in the mine, and elapsed time between mining and the roof fall. The major difficulty in controlling roof falls in the design stage is the prediction of their size, frequency and location with any degree of reliability. Once accurate prediction is possible steps can be taken to provide adequate support. Ideally, for future planning in new mining areas, one should be able to take information from core drilling and logging and use this to predict the location, likelihood, time and size of roof falls for any specified mining plan. Specific probabilities can be assigned to the occurrence of roof falls for a particular mine within a given geologic setting. Given the uncertainties in predicting roof falls, determination of the optimum balance between costs due to roof falls and actual savings effected by increasing support costs to reduce roof falls is best achieved using a probabilistic approach. The final decision on the amount of support and room width must be determined based on minimization of mining costs. Based on this research the following conclusions can be made: (1) roof rating systems offer realistic and readily usable techniques for ground failure prediction and evaluation, (2) probabilistic simulation methods are most suitable for roof control situations with a high degree of uncertainty and complex interactions, and (3) using the simulator program rocsim as a predictive tool enables the mine designer to optimize the choice of a ground control plan by allowing the advantages of a given plan to be seen in relationship to its true cost.
Mining-industry; Underground-mining; Rock-falls; Rock-mechanics; Ground-control; Ground-stability; Structural-analysis; Coal-mining; Failure-analysis; Simulation-methods; Control-systems; Engineering-controls; Geology; Gonadotropic-hormones; Analytical-instruments; Work-operations; Work-practices
OP; Conference/Symposia Proceedings
Rock Mechanics: Contributions and Challenges: Proceedings of the 31st U.S. Symposium, June 18-20, 1990, Colorado School of Mines, Golden, Colorado
Virginia Polytechnic Institute and State University (Virginia Tech)