Energy evolution mechanism of hard roof of working face adjacent to goaf after hydraulic fracturing and application

To solve the unclear energy evolution mechanism and uncertain fracturing effects in hydraulic fracturing of coal seams adjacent to goafs, this study explored hydraulic fracturing's influence on roof energy release via theoretical analysis, proposed the optimal fracturing location to mitigate inter-roof energy transfer, and clarified fractures' regulatory effects on key strata through particle flow numerical simulation. Combined with field tests, it revealed the fractured roof energy evolution law: key stratum movement triggers energy release, and hydraulic fracturing promotes the phased subsidence of key strata by generating directional fractures. The elastic potential energy accumulated during this process is converted into gravitational potential energy in phases, and the specific conversion efficiency depends on the spatial distribution of the fracture network. Calculations show energy release is reduced by 95% (to 35,133.16 J) versus the unfractured condition. The optimal fracturing location is within 31.2 m of the return air roadway. Numerical simulation and field data confirm hydraulic fracturing promotes fracture development, alters stratum movement, reduces abutment pressure and high-energy microseismic events, and alleviates stress concentration, ensuring safe and efficient coal mine production.