A simplified conceptual model for estimating roof bolting requirements

Summary The selection of rock bolting lengths and spacings for a mine roof or back is relatively straightforward when wedges of rock bound by discrete discontinuities require support, or when the immediate roof can be anchored into a recognizably stable layer or rock mass. When neither of these situations is present the choice of bolt lengths and spacings is more difficult.In this paper a simplified conceptual model is presented which invokes the concept of an ellipticallyshaped zone of loosening above the opening, all, or a portion of which, may require support. The analysis includes the influence of opening span, height,in situ stress state, and rock mass quality as measured by the CSIR Rock Mass Classification.Validation of the model was sought by analysing a number of case histories in the literature.