Shear behavior of rock joints and comparative study on shear strength criteria with three-dimensional morphology parameters

Three groups of rock joints with different morphologies are made from cement mortar materials. The shear behavior is investigated by means of the direct shear tests under constant normal stress condition. The effects of the applied normal stress and morphology on the shear strength are analyzed. According to the experimental results, it can be found that the peak dilatancy angle decreases with the increasing normal stress and increases with the increasing roughness. The shear strength increases with the increasing normal stress and also the roughness of rock joints. The reason of underestimation by JRC-JCS criterion is analyzed, and it is suggested to adopt the three-dimensional morphology parameters and tensile strength to capture the characteristics of the peak shear strength. The hyperbolic criterion is suggested to use as a predictive tool to assess the peak shear strength of rock joints under low normal stress level based on the comparisons among several criteria with three-dimensional morphology parameters.