Abstract
Abstract
Aiming at the frequent occurrence of instability disasters at mining faces with hard roof and high-gas soft coal seams in a coal mine in Shaanxi Province, this paper systematically investigates the disaster-causing mechanism of face instability and corresponding prevention and control technologies by combining field statistical analysis, theoretical calculation, UDEC distinct element numerical simulation, uniaxial compression tests on gas-bearing coal, and field industrial tests. The research results show that face instability is induced by the coupling effect of periodic weighting of hard roof and residual gas pressure. Periodic weighting significantly aggravates stress concentration at the working face, while the increase of gas pressure reduces the uniaxial compressive strength of coal by nearly 50%, and the combined action of the two factors greatly raises the risk of coal wall instability. Deep-hole pre-splitting blasting implemented at an interval of 20 m reduces the periodic weighting interval of the working face by 51.27% and effectively weakens the weighting intensity of the roof. For soft coal seams with a firmness coefficient ranging from 0.12 to 0.58, the cross-measure hydraulic reaming technology can lower the residual gas pressure to below 0.21 MPa with uniform distribution, realizing efficient pressure relief and permeability enhancement. Field tests verify that the combined technology of deep-hole pre-splitting blasting for roof + cross-measure hydraulic reaming in floor roadways can drastically cut down the frequency of face instability. The research findings provide theoretical basis and engineering references for the prevention and control of instability disasters at mining faces under similar geological conditions.