Bulk-scale testing of frictional properties of rock

Abstract

An important aspect of designing engineering structures in or on a rock mass is a thorough understanding of the physical properties of the mass, as well as factors that may alter those properties. Engineers involved in the evaluation of structural soundness of a rock body for mining or slope stability purposes are particularly interested in the angle of sliding friction. It is defined as the angle at which a rock mass will slide or fail along a plane of weakness, i.e. a joint, fault or discontinuity. The angle of friction is one of the quantities used to predict the shear strength of a discontinuity using well-documented relationships such as the Coulomb Criterion. Laboratory testing of samples of granite, basalt, and sandstone using a sliding table apparatus, designed to simulate discontinuity conditions at or near the earth surface, is an attempt to investigate correlation's between sliding friction angle and factors such as normal force, sliding surface roughness and surface area. Results obtained from testing can be contrasted against related frictional data estimated in the field as a means with which to evaluate the reliability of the estimation method. Results from other test methods can be compared to sliding test data to investigate the influence of the testing system on material response.