Experimental Study on Shear Characteristics of a Rock Joint Subjected to Dynamic Shear Load

Exploring the mechanical response of rock joint subjected to dynamic shear load is essential for revealing the mechanism of dynamic disasters in jointed rock masses. Using an impact-induced direct-shear method, a series of dynamic shear experiments were conducted on artificial granite joints with regularly undulating interface. The dynamic friction coefficient of joint was first obtained from planar jointed granite specimens before the dynamic shear strength and shear displacement of the regularly undulating joints were tested. During the test, the effects of normal stress and shear rate were both considered. The results show that when the shear velocity ranges from 1 to 9 m/s, the dynamic friction coefficient of the planar joint is negatively correlated with shear velocity, and decreases by at least 50% compared with that under quasi-static condition. The rate dependence of shear strength appears opposite for granite joints with undulating angles of 11.3° and 26.6°, respectively. A shear strength model for rock joint with an undulating angle of 11.3° is then suggested based on the test results. During impact shear sliding, the maximum shear displacement of the joint is linearly negatively related to the initial normal stress. While, non-driven sliding may occur under low normal stress and high impact velocity, which leads to a large magnitude of shear slip. Highlights The shear strength and shear displacement of rock joints are tested with shear rate ranging from 1 to 9 m/s. The rate dependence of shear strength appears opposite for rock joints with sharp and gentle undulation and a shear strength model is suggested. Besides impact-driven sliding, the non-driven sliding may also occur in the joint under low normal stress and high impact velocity.