Development of new peak shear-strength criterion for anisotropic rock joints

The roughness of a natural rock joint was measured in different directions using a laser profilometer. Two stationary roughness parameters and a nonst ationary roughness parameter (all fractal based) were used to quantify anis otropic roughness. A plaster of Paris based model material was used to make model material replicas of the natural rock joint. Direct shear tests were performed at five different normal stresses, in each of the directions tha t were used for the roughness measurements, to measure the anisotropic peak shear strength of the model joint. Required observations and experiments w ere conducted to estimate (1) the asperity shear area as a proportion of th e total surface area of the joint, for each tested joint; (2) the basic fri ction angle of the model material; and (3) the joint compressive strength. Tests were also conducted to develop a peak shear-strength criterion for th e intact model material. Part of the direct shear test data was used to dev elop a new peak shear-strength criterion for joints including the aforement ioned parameters. The other part of the data was used for model validation.