Application of pre-splitting blasting roof-cutting pressure relief technology for roadway protection under hard roof.

Abstract

The 360,606 working face of Xinji 1^# Mine was taken as an engineering case to address the significant safety hazards associated with coal mining under hard roof. A key technical scheme for pre-splitting blasting roof-cutting pressure relief was developed by theoretical analysis, numerical simulation, and field experiments. The results are as follows. (1) Fracture propagation was dominated by synergistic effects of explosion gases and stress waves. Explosive energy was concentrated at crack tips after exploration. When accumulated energy exceeded the rock's deformation capacity, cracks propagated further. (2) Explosive energy distribution was optimal between the crushing zone and fracture zone at a decoupling coefficient of 1.5, which avoided energy waste from over-fragmentation. A 5-m spacing yielded a peak effective stress of 98.6 MPa at the midpoint between boreholes. Integrated stress cloud analysis indicated that a spacing of 5 m was optimal. (3) Post-implementation displacements were measured as follows: roof (238 mm), coal pillar sidewall (124 mm), mining sidewall (100 mm), and floor (48 mm). The successful retention of the 306,606 working face gateway validated the efficacy of this technology in roof-cutting and roadway protection. These findings provide technical guidance for coal extraction under analogous engineering.