The Effect of Asperity Inclination and Orientation on the Shear Behavior of Rock Joints

Abstract

Abstract This study investigates the effect of asperity inclination angle and asperity orientation on the shear behavior of rock joints under constant normal loading conditions. The effects of these two rock joint characteristics were investigated by creating artificial rock joints having a regular pattern of triangular asperities that were oriented at different angles in the plane of shear. Large-scale direct shear tests were conducted over a range of normal stresses, on 0.30 × 0.30 m gypsum blocks containing well-mated joints with different asperity orientation and inclination angle characteristics. Experimental results illustrate the importance of considering both the asperity orientation with respect to the loading direction and the applied normal stress when predicting the shear behavior of rock joints. In general, higher normal stresses increased the stiffness of the rock joints in shearing, while a reduction in the shear strength of the rock joints was observed when increasing the asperity orientation angle. The dilation curves indicated the occurrence of both dilation and lateral displacement during shearing. Two different techniques are used to quantify the condition of the joint surfaces: the first approach utilizes the concept of fractal dimension, and the second utilizes the concept of potential contact area. These approaches can be applied in a useful fashion within the framework of existing shear failure criterion for oriented rock joints.