The development of a coal measure classification (CMC) and its use for prediction of geomechanical parameters

Abstract

Many studies have been performed to predict the strength and deformation moduli for both rock masses and discontinuities. However, in most empirical equations in the literature that have been proposed for the estimation of the strengths and deformation moduli, the rock mass is assumed isotropic. Although it is known that the strength and deformation of a stratified rock mass varies depending on the loading direction in relation to the orientation of the lamination planes, there exists at present no commonly accepted method for characterising this anisotropy. This paper outlines the development of a rock mass rating system for coal measure rock masses that can be used to empirically predict the engineering properties of stratified rock masses. The output from the classification system is two numerical ratings representing the different engineering properties of the strata in directions parallel and perpendicular to stratification. A detailed description on the methodology used to develop the classification system has been given and the derivation and rating of the various rock mass parameters is outlined. The methodology of deriving the in situ stratified rock mass input parameters and geomechanical computational analysis is illustrated for the case of two rock bolted roadways within a representative deep UK coal mine. The model predictions were validated against the actual in situ monitoring data of displacements within the immediate roof of the roadway.