Coal pillar bumps involve the sudden expulsion of coal and rock into the mine opening. Cleating is a type of joint system unique to coal seams. Cleat systems differ from adjacent joint systems in that they are pervasive throughout the coal seam, and are much more tightly spaced than joints that occur in other rock types. This study assumes that if elastic energy remains in the rock mass to a greater extent than plastic energy, the risk of pillar bursting would be increased proportionally to the energy ratio. In order to investigate and quantify the risk posed by this possible imbalance, a 3D finite difference code (the FLAC3D model) is used so that the elastic strain energy and dissipated plastic energy could be tracked for given zones in the model. Various orientations of cleat and applied stresses in the pillar are considered as input data and to determine the boundary conditions for the analysis. The results show the ratio of stored elastic energy to dissipated plastic energy.

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