The Effects of Surface Roughness on the Shear Strength of Joints in Rock

摘要

The shear strength of a discontinuity, or joint, in a rock mass is derived from two components: (1) the frictional component offered by two flat surfaces sliding relative to one another, plus (2) the geometrical component derived from the necessity of interlocking surface irregularities to be overridden or sheared off as sliding commences. The chief purpose of this investigation has been to determine the manner in which surface preparation affects the frictional component of shear strength. Flat surfaces in basalt, dolomite, limestone, sandstone, siltstone, granite, and schistose gneiss, prepared by lapping with fine no. 600 grit, by lapping with coarse no. 80 grit, and by sandblasting, have been sheared wet and dry under normal pressures from 10 to 1000 psi. To supplement test data from the flat surfaces, tests were also performed on natural joints in granite and siltstone, on joints in granite grouted with neat cement, and along intact bedding in two shales. In all, approximately 1000 shear tests were performed using a high-capacity directshear machine designed specifically for this testing program. (Author)