Regional fracturing technology for pressure relief and rock burst prevention in thick and hard composite sandstone roof and its application

The 3-1 coal seam in Menkeqing Coal Mine has strong propensity for rock burst. Given the large coal seam burial depth, high mining intensity, and the presence of a thick composite sandstone roof overlying the coal seam, rock burst disasters are likely to be induced during mining of the working face. Conventional pressure relief measures targeting medium- to high-position thick and hard roofs are limited in both treatment height and range, often failing to achieve the desired pressure relief effect. In response to this problem, dominant disaster-inducing factors for rock burst were analyzed first. On this basis, roof lithology analysis, key strata theory calculation, microseismic monitoring, and strata fracture energy transfer calculation were performed to identify the dominant strata responsible for rock burst and reveal the mechanism of regional fracturing with long boreholes for pressure relief and rock burst prevention. Furthermore, the engineering practice of regional fracturing with long boreholes was conducted, and the corresponding effect analysis was carried out. The results show that the large burial depth of the working face provides sufficient foundation static load. The 3-1 coal seam and its roof and floor have the potential to generate rock burst, and the dynamic load arising from the breakage of the highly integral and continuous composite sandstone roof is the main source triggering rock burst. Regional fracturing with long boreholes was used for advanced prefracturing of the thick and hard composite sandstone roof. After the construction was completed, cracks propagated notably in fractured strata, and a remarkable prefracturing effect was achieved. During mining of the working face, the frequency, energy, and concentration of high-energy microseismic events in the fracturing area were significantly reduced, the intensity and distance of periodic weighting of the working face decreased. The engineering practice demonstrates the effectiveness of regional fracturing with long boreholes in significantly reducing the risk of rock burst disasters and ensuring safe mining of the working face. The research results can provide reference for the prevention and control of rock burst in coal mines with similar conditions.