Mechanical Behavior of Rock Joints with Various Kinds of Joint Surface Roughness under Cyclic Direct Shear Loading Conditions

This study investigates the cyclic shearing behavior of simulated natural rock samples with three kinds of natural joint surface roughness under different confining pressure conditions. The experimental results contribute to the understanding of various mechanical behaviors and the differences among them after a series of shear cycles. Mechanical properties, such as the Joint Roughness Coefficient (JRC), the shear stiffness of the joint after shear, the dilation in the joint during shear, the peak and residual stress levels and the amount of gouge material during shear, were obtained. In this study, the influence of the gouge material obtained after shearing has also been investigated. As from an earlier study conducted by Kishida and Sakurai (2007), it has been proven to have a bearing effect on later cycles, namely, causing a reduction in the residual friction of a joint. The mechanical properties (shear strength, joint dilation, shearing stiffness, peak shear displacement, etc.) depended on the surface roughness of the joint characterized by the JRC, the normal loading applied and the loading cycles. These can be helpful when investigating the weak nature of rock slopes under dynamic loading conditions.