Blasting stress characteristics of fan-pattern holes in coal-rock media

Based on a lot of mining experiments, a representative blasting engineering was studied by three-dimensional numerical simulation. A numerical computational model of coal-rock media was constructed for the through strata blasting. Effective stress changes at different locations with time were acquired, and the difference in the decrease of effective stress with increasing distance was analyzed in different gas draining holes. Numerical simulation results show that the maximum radius of the area ruptured is up to 1.4 and 1.8 m for the top and bottom of the hole in the multi-media, respectively. The average value of effective stress in the bottom of the hole is 73% higher than that in the top at the same distance due to stress wave interference and reflection in the bottom of the hole. The blasting effect for a coal seam in the multi-media is better than that in a single coal seam. Under the same condition, the maximum value of the effective stress at the top and bottom of the hole in the multi-media is 17% to 42% and 6% to 24% higher than that in a single coal seam, respectively.