Numerical study of jointed rock fractures with different shapes of joint asperities using a 3D hybrid finite-discrete element method

Abstract

With the increase in the number of rock engineering projects, it has been recognized that the influence of joints on dynamic damage of rock mass cannot be ignored. Existence of joints in the rock mass having complex surface configurations significantly influences its damage process. Hence, it is of great interest to study the effect of joint surface configurations on dynamic damage of jointed rock. In this study, a 3-dimentional numerical model based on the hybrid finite-discrete element method (FDEM) for split Hopkinson pressure bar (SHPB) system was built to investigate the dynamic fracturing process of jointed rock. The jointed rock model was designed as a combination of two cubic blocks with rough asperities and smooth surfaces. These asperities have a triangular, trapezoidal, and arc-shaped shapes (simplified from the Barton’s standard joint surface profiles), which were arranged in the middle position for eliminating the boundary effect. The effects of shapes of joint asperities on fracturing process and failure modes of jointed rock were simulated and analysed. The numerical results indicated that the crack prorogation is that the first cracks are distributed at the end of the specimen in contact with the bar and nearby joint asperity, then coalesced with each other along the loading direction. The joint asperity shapes have also a significant influence on failure mode, which is expressed the composite tensile-shear failure and splitting tensile failure, In addition, the triangular joint asperity are prone to damage the facing rock.