Research on the mechanism and effect of sandblasting jet axial roof cutting technology for rock burst prevention

Sandblasting jet axial roof cutting technology has been developed in recent years, but its mechanism for rock burst prevention is not yet fully understood. Based on the work at the 20101 face of the Dahaize Coal Mine, theoretical analysis and field measurements were used to analyze the spatial structural characteristics of the overlying strata before and after the application of the sandblasting jet axial roof cutting technology. The impact of roof cutting on the energy accumulation in thick hard rock layers and the distribution of lateral support pressure was studied, revealing the mechanism of rock burst prevention of the sandblasting jet axial roof cutting technology. The conclusions are as follows: ① The application of sandblasting jet axial roof cutting technology increases the fractures in the roof strata, causing the short-edge fracture line of the roof to move forward, reducing or eliminating the cantilever effect, and lowering the static support pressure beneath the roof cutting area. At the same time, the roof collapses promptly after cutting, providing support for the overlying strata, reducing the energy accumulation in the upper strata and the dynamic load pressure generated by the roof weight, thereby reducing the risk of rock bursts. ② Using transient electromagnetic detectors and statistical methods to measure the drainage speed of desorption holes, the apparent resistivity and drainage speed of the roof before and after cutting were detected and statistically evaluated. Compared to before cutting, the apparent resistivity of the upper strata significantly increased after cutting, while the apparent resistivity of the lower strata increased locally. Meanwhile, the average drainage rate of the desorption holes increased to 0.88 m3/h, a 1.47-fold increase, indicating that the water content in both the upper and lower strata significantly decreased, the drainage speed increased, and the fractures in the roof significantly increased, demonstrating good cutting effectiveness. ③ Microseismic and support resistance monitoring results at the 20101 face show that after the application of sandblasting jet axial roof cutting technology, the end roof collapsed promptly without forming a cantilever. The end-cycle support resistance increased significantly, while the total energy, total frequency, and high-energy event frequency of microseismic events decreased by 56.50%, 63.02%, and 33%, respectively. Additionally, the distance of microseismic events from the working face coal wall increased by 30 meters along the strike direction, and the frequency decreased in the dip direction. The roof fracture height reduced from 145 meters to 75 meters.