Progressive degradation on the shear behavior of artificial joints before residual failure

Two types of artificial joints with tooth-shaped asperity under repeated direct-shearing are performed in this experimental research. The progressive failure mechanism and strength degradation of rock joints after peak strength are monitored during shearing. The progressive degrading of shear strength parameter or index is examined according to three strength criteria. Some conclusions are drawn as follows. (i) The initial angle of tooth seriously affects the shear mechanism of joints. The rougher surface demonstrates a more brittle failure. (ii) The degradation behavior is path-dependent. The degrading rate of strength is depended on the tooth shape, and the normal stress levels. (iii) The dilation angle also decreases progressively with displacement increasing. The residual state is rougher than the basic friction property even under a large displacement.