Experimental and numerical studies on dynamic fracturing behavior of roughly jointed rock

The surface roughness is an important feature of rock joints. Its effect on the mechanical properties of joints is significant in characterizing dynamic failure of natural rock masses. Both laboratory experiments and numerical simulation analysis were conducted to investigate the dynamic fracturing of roughly jointed granite under various loading rates. The modified split Hopkinson pressure bar apparatus with square-shaped bars and an in-house 3D hybrid finite-discrete element method are used in this study. One surface of the specimens with three striped trapezoidal bulges was adopted to simulate the artificially rough joint. The striped bulges are centrally arranged in the middle of joint surface to minimize the influence of specimen boundary on cracking process. The test results revealed that the surface roughness has a significant effect on dominating dynamic fracturing behaviors of jointed rock and loading rate affects the dynamic response and fracture patterns of these jointed rocks. The simulation further illustrated the dynamic stress propagation and corresponding fracturing process of the roughly jointed granite under dynamic loading. Additionally, the effect of free boundary of the specimens and joint contact properties on fracturing behavior of jointed rocks are numerically analyzed. These findings from both the dynamic experiments and numerical modelings are expected to provide fundamental knowledge for understanding the dynamic properties of natural jointed rock masses.