Study On The Pressure Relief Effect In Gob-Side Coal Body During Mining An Inclined Longwall Panel

This study combined multi-field coupled numerical calculations and field measurements to analyze the gas pressure relief and the outburst elimination range of the coal body in the lower side of a gob induced by excavating an inclined seam. A coal seam gas flow solid-gas coupled model allowing for elastoplastic damage was established based on an inclined longwall panel of the Hongyan Coal Mine in Chongqing, China. To inspect the gas depressurization effect, this study simulated the collapse and damage of strata surrounding the longwall panel after mining by using a constitutive model of the interlayer weak plane, the changes in the damage, gas pressure, and stress concentration in the gob-side coal seam were analyzed numerically. Besides, variation in gas pressure within 10-23 m away from the panel margin was measured on-site during the advancement of the longwall face to validate and modify the results of modeling. The simulation results showed that the advancing of the panel is highly effective in releasing gas from the gob-side coal body. The rupture penetration, stress concentration, and original elastic zone will be formed in the gob-side coal body with increasing distance away from the gob after mining the 3603-2 panel. The permeability increased dramatically and the gas was almost exhausted in the rupture penetration zone. The field measurement results indicated that gas pressure decreased in three stages with advancement. After completion of excavation activities, the drop rates of gas pressure and gas content within 10-23 m from the gob were 26.55%-73.58% and 34%-71%, respectively. Additionally, it was proved that the numerical simulation results were instructive for predicting the range of gas outburst-proneness elimination belt by comparing simulation and field results, and the outburst elimination range of the inclined longwall panel of the Hongyan Coal Mine was determined to be 10 m.