Improvement of the Mechanical Shear Model for Rock Joints Considering the Bearing Effect

A theoretical mechanical shear model for single rock joints has been developed which can systematically express the shear behavior of rock joints by inputting the normal confining stress, the uniaxial compressive strength of the intact material, information on the geometry of the rough joint surface, and the basic friction angle. This model is able to show the process by which the shear stress increases, reaches the peak stress, decreases (strain softening), and then gradually arrives at the residual state. Moreover, variations in the joint surface roughness can be presented in the shear process. In some cases of comparisons between the experimental and the analytical results, errors have been found in the residual state. Therefore, the authors have given thought here to the reason for the occurrence of the bearing effect of the shaved powder material in relation to these errors. In this paper, the mechanical shear model is improved in terms of the bearing effect. Then, by comparing the experimental results with the analytical results, the validity of the modified model is discussed.