Roof collapse accumulation and mining stress evolution characteristics of double inclined mining in steeply inclined medium-thick coal seam

Abstract :Longwall comprehensive mechanized mining method for steeply inclined medium-thick coal seams above 60 ° urgently needs to be broken through. Taking the 3212 working face of Sichuan Lvshuidong Coal Mine as the engineering background, based on systematic research and field practice, the mining method of double-inclined mining is proposed on the basis of dip-pseudo-inclined mining. The advantages, engineering difficulties and hidden dangers of double-inclined mining are clarified. Physical similarity simulation and numerical simulation are used to analyze the filling and sliding accumulation law of broken gangue in the basic roof of double-inclined mining and the evolution process of roof stress. The results show that the layout of the double inclined mining face needs to be coordinated with the mining design of the mine, and the maintenance of the two lanes of the working face is difficult. Among them, the side of the return air lane is greatly affected by the mining stress, and the coordination between the transport lane and the working face support is difficult ; due to its special-shaped goaf roof structure, the double-inclined mining has a larger caving step, and its gangue caving accumulation is inverted triangle and has periodic sliding characteristics, and the non-uniform weighting phenomenon of the upper and middle parts of the working face caused by the accumulation of large gangue. The stress of the original rock in the double in-clined mining increases gradually with the advance of the working face, and the pressure intensity of the upper, middle and lower parts of the working face is different. Generally, the pressure in the upper part of the inclined middle is greater than that in the lower part, but the stress concentration coefficient of the sup-porting pressure in the lower part of the inclined is greater than that in the upper part of the working face. The stress evolution characteristics of the roof in the double inclined mining are affected by the shape of the working face and the advancing distance, and the stress release range is gradually reduced from the upper part of the inclined to the lower part due to the effect of the inclined angle of the roadway.