Research and engineering practice on weakening technology of key strata in hard roof

In response to the technical challenges of severe strata behavior and frequent rock bursts caused by the hard and thick roof in the ZF4405 working face of Xiagou Coal Mine, this paper proposes and implements a collaborative control technology combining directional long-hole hydraulic fracturing with roof blasting pressure relief. Through theoretical analysis, numerical simulation, and engineering verification, systematic research was conducted on the weakening mechanism of key strata, optimization of process parameters, and evaluation of engineering effectiveness. The results show that, The thickness and elastic modulus of the medium-grained sandstone key stratum are the main controlling factors affecting roof stability. By establishing a mechanical model for key stratum fracture, it was determined that fracturing boreholes should be arranged in the tensile stress concentration zone of the rock mass beneath the key stratum; A phased composite weakening technology was adopted, forming a radial fracture network during the fracturing stage and achieving directional expansion along fracture surfaces during the blasting stage, with the synergy of both further weakening the key stratum; After project implementation, the periodic weighting interval was reduced from 22 m to 17 m, the peak working resistance of supports decreased by 36%, roadway floor heave was reduced by 76%, top coal recovery rate increased by 8.2%, and cumulative economic benefits reached 92.94 million yuan. Monitoring data showed a 25% reduction in total microseismic event energy, verifying the effectiveness of the technical system. The research results provide a new technical approach for preventing hard roof disasters in mine.