Numerical Simulation of Blasting in Jointed Rock Mass and the Quantitative Statistics of Cracks

In the process of blasting rock breaking, the existence of joints and fissures in rock mass affects the blasting crushing effect. Some finite element numerical simulation software can realize the blasting rock breaking simulation of jointed rock mass, while it is difficult to realize the quantitative description of cracks. A numerical model of jointed rock mass was established using LS-DYNA software to analyze the obstruction and reflection effects of joint surfaces on explosion stress waves. The images of blast-induced cracks were binarized, and crack extraction from the binary images was achieved using the Hough transform method. Statistical results of the crack images were subsequently analyzed through the maximum likelihood estimation method. The results show that: The existence of joints seriously hinders the propagation of blasting stress wave, and the peak stress is reduced by about 60%. The rock mass between blast hole and joint is subjected to stronger stress superposition due to reflection, and the crushing effect is more remarkable; In the initial stage of explosion, the occurrence probability of small cracks is large, and at the end, it is dominated by long cracks. In this process, many short cracks expand into long cracks, and the distribution of crack angles is relatively average. The distribution of long cracks with joint angles of 45° and 60° is more uniform, and the extreme value is not obvious. When the joints are 15° and 30°, the crack development in the vertical direction is obvious. The Hough transform method realizes the quantitative result statistics of crack images in the numerical simulation results.