Evolution and management of thick-hard roof using goaf-based multistage hydraulic fracturing technology—a case study in western Chinese coal field

The mining-induced breaking of thick-hard roof is characterized by the microseisms and energy release. To preliminary control rock burst caused by the breakage of the thick-hard roof in panel #42202 of Shengdong coal field, a goaf-based multistage hydraulic fracturing technology was developed, and corresponding mathematical model for hydraulic fracturing position determination and synergetic support system comprised of collapse filling, coal pillars, and load-bearing strata were established. The results show that a distressed zone with a height of 29 m along the drilling direction and a width of 230–300 m along the radial direction of the drilling hole was created. Compared with the effect of single-hole fracturing, the influence scope increased into 70 m for double-hole fracturing. The hydraulic pressure gradient drop of 12.8 MPa was observed, as the termination of hydraulic fracturing with an initiation hydraulic pressure of 33.1 MPa. Additionally, the mining weighting period interval, front abutment coefficient, peak pressure, and roadway surrounding rock stress were reduced by 20.0–69.7%, 5.8–7.9%, 13.4–18.6%, and 22.2–32.1%, respectively.