Abstract:
Addressing the challenge of inducing strong mining pressure dynamic disasters when mining shallowly buried, close-proximity coal seams overlying residual coal pillars, this study uses the 30210 working face at Nanliang Coal Mine as its engineering context. This study employs a combined approach of theoretical analysis, numerical simulation, physical modeling, and field measurements to investigate the rock pressure patterns in the mining face beneath the residual coal pillar. It reveals the mechanisms underlying severe rock pressure disasters and proposes a “spatial zoning-mechanical coordination” technique for advance zone weakening through directional drilling and hydraulic fracturing. The study indicates that during coal pillar extraction, the pillar and its overlying critical load-bearing structures undergo sudden instability due to mining disturbance. Accumulated elastic energy is instantaneously released as kinetic energy into the mining area, readily triggering severe rock pressure disasters. Based on the prevention strategy of “fracturing collapse support - three-dimensional zoned weakening of key strata - stress transfer path diversion,” a hydraulic fracturing technology system for spatial zoned synergistic weakening was established and validated through physical simulation. By creating an artificial fracture network, the system induces premature failure of the coal pillar's stress-concentrated interlayer strata and redirects overburden loads toward the rear collapse mass. This reconfigures stress pathways, reducing cyclic pressure advance intervals to 8-16 m and lowering peak advance support pressure to below 9.26 MPa. The field fracturing results show that the fracturing pressure curve fluctuates in a ' serrated ' manner, and the pressure drops sharply by 1.5-6 MPa at the moment of fracture initiation. The hierarchical release mechanism of energy from ' instantaneous impact release ' to ' staged slow release ' was constructed. After the treatment, the pressure step distance was shortened to 8 ~ 13 m from 18 m before the treatment, and the peak pressure and average resistance decreased by 18% and 22% respectively. There was no strong rock pressure in the process of working face advancing, and the coordinated control of ' stress structure energy ' was realized.