UNIVERSITY OF NEW SOUTH WALES COAL PILLAR STRENGTH DETERMINATIONS FOR AUSTRALIAN AND SOUTH AFRICAN MINING CONDITIONS

A series of mine design accidents in the late 1980s resulted in a major research program at the University of New South Wales, Australia, aimed at developing pillar and mine design guidelines. A database of both failed and unfailed Australian underground coal mine pillar case studies was compiled. A procedure was developed to enable the effective width of rectangular pillars to be taken into account. The database was analyzed statistically using the maximum likelihood method, both independently and as a combined data set with the more extensive South African database. Probabilities of failure were correlated to factors of safety. It was found that there was less than a 4% variance in pillar design extraction ratios resulting from each of these approaches. There is a remarkable consistency between the design formulas developed from backanalysis of the two separate national pillar databases containing many different coal seams and geological environments. Professor and Head, School of Mining Engineering, University of New South Wales, Sydney, Australia. Professor, School of Mining Engineering, University of New South Wales, Sydney, Australia. Distinguished professor, School of Mining Engineering, Colorado School of Mines, Golden, CO.