Mining conditions imposed by a coal seam roof can be analysed according to natural causes, before consideration of strata control._x000D_
All types of roof behaviour can be explained by considering only three independent variables. They are roof rock types, rock stresses and discontinuities. Roof rock types encountered in the Sc.ithern Coalfield of New South Wales (NSW) are sandstone, shale, mudstone, laminite and coal. Each rock has its own mode of failure._x000D_
Lithological stability of the sediments varies from one type to another. Regional stresses upon a coal seam roof will vary in magnitude according to the proportion of gravitational stress, which is related to depth of cover, and residual stress, which is related to the maximum depth of burial and may be gauged by coal rank. Local stresses will vary according to tectonic deformation, related to irregularities in seam structure.