The effect of secondary sawtooth height on shear properties of rock joints with rigid contact

Abstract

A variety of joints of various shapes are widely developed in rock masses. An accurate account of the behavior of a joint rock mass requires a realistic model for the tribological behavior of joints, which requires further study to understand the influence of secondary asperities on shear strength and the shear failure mechanism of joints. In view of the current lack of research on the effects of secondary asperities, a test scheme including first-order and second-order sawteeth of different heights was developed. By means of a physical model test and numerical model test under different constant normal stress conditions, the macroscopic mechanical properties and the microscopic deformation failure process affected by secondary sawtooth of joint are revealed, respectively. The results of the direct shear tests under different normal stresses on these sawtooth profiles demonstrate that the height of the second-order asperity has a certain effect on the shear strength. When the secondary sawtooth height is less than half the height of the first-order sawtooth, the shear strength increases with secondary sawtooth height. Compared with the joint surface of the same sawtooth height, the presence of a secondary sawtooth causes local stress concentration of the joint under the direct shear test, resulting in different microcrack production, expansion sites, and numbers of microcracks. We believe that this study is useful for understanding the shear characteristics of saw-toothed joints.