DEM studies of cracking behavior of jointed rocks with different matching states under impact loading

Joints assume crucial roles in the propagation of stress waves for dynamic disasters. The SHPB system and jointed rocks with two matching states were numerically constructed. The mismatched joint comprises a triangular-shaped rough surface and a flat surface, whereas fully matched joint consists of rough surface and its biting surface. Subsequently, dynamic cracking behaviors and stress distribution of these jointed rocks subjected to different loading rates were examined. The simulated rock parameters are obtained based on cement mortar experiments. The results indicate that the dynamic strength of jointed rock is proportional to loading rate. Meanwhile, the strength and average modulus of mismatched jointed rocks (MJR) are significantly lower than those of fully matched jointed rocks (FJR) under the same loading. Stress concentration occurs at the tips of the mismatched joint and is readily influenced by the joint matching state. Owing to these rough joint surfaces, the MJR cracked first near the triangular teeth and expanded from the root of the teeth to both sides. However, the FJR was less affected by the joints and resembled that of intact rocks. Additionally, the effect of the joint undulation angle and the P-wave duration on the cracking behavior of jointed rock was also deliberated. The higher the joint undulation angle, the greater the concentrated stress.