Coupling Model of Stress-Damage-Seepage and Its Application to Static Blasting Technology in Coal Mine

Most coal mine field application processes are carried out using empirical formulas because of the insufficient understanding of the fracture development law of the static blasting technology. This lack of understanding results in poor coal seam gas extraction. In this study, a stress-damage coupling model was established to investigate the construction parameters of the static blasting technology using COMSOL simulation software. Then, a stress-damage-seepage coupling model was designed to study the evolution of the fracture field (seepage field) during the static blasting process using realistic failure process analysis simulation software. Finally, the influencing factors and fracturing effects were analyzed comprehensively. The research results show the following. (1) Comparing the simulation results with previous field tests reveals that the seepage law of the numerical simulation of the static blasting technology is consistent with the field test results, verifying the rationality of the stress-damage-seepage coupling model. (2) The development of coal seam fractures is affected by the expansion pressure, elastic modulus, and guide hole arrangement; the guide hole arrangement can play a role in guiding the development direction of fractures and enhancing the effect of fracturing. (3) The coal body mainly experienced the following five stages of fracturing: coal body compaction, microdamage formation, microfracture formation, large fracture formation, and fracture propagation. In addition, because of the rapid release of soundless cracking agents during the large fracture formation stage, the gas flow decreased in a short time. (4) The static blasting technology causes the coal seam permeability coefficient to increase. Compared with conventional extraction, the effective influence radius in the horizontal direction increases by 5.1 times, and the effective influence radius in the vertical direction increases by approximately 3 times. The static blasting technology can increase the number of coal seam fractures and significantly reduce the coal seam gas pressure, thereby enhancing coal seam permeability and realizing safe coal mining.