A Peak Shear Displacement Model Considering Three-Dimensional Roughness of the Actual Contact Joint Surface

During rock joint shear tests, only some steep asperities on the shear surface participate in the shearing process. The existing peak shear displacement (PSD) models fail to reflect the role of steep asperities on the PSD fully. Therefore, this study proposes a new PSD model of rock joints to solve this problem. First, shear tests are carried out on red sandstone joint samples with the same morphology under different normal stress. The results show that the PSD increases with normal stress and decreases with joint surface roughness. A PSD model for rock joints considering the three-dimensional unevenness of the actual contact joint surface and normal stress is presented. The model reflects that the PSD increases with the normal stress because the increase of the normal stress leads to a decrease of the actual contact joint roughness, and the decrease of the roughness leads to an increase of the PSD of the joints. The new proposed model further shows that the roughness of the actual contact joint surface can well reflect the shear process. The test results of different studies describing the various types of joints verify the rationality of the proposed PSD model of rock joints, following which the adaptability and limitations of the model are discussed.