Geo-dynamic conditions instability and support optimization of semi coal-rock roadway in large inclined and extra thick coal seam

In order to clarify the instability mechanism of semi coal rock roadway in highly inclined and extra thick coal seam and improve the stability of roadway, taking the semi coal rock roadway in the highly inclined and extra thick coal seams of Wudong Coal Mine in Xinjiang as the engineering background, the geo-dynamic environment of semi coal-rock roadway in Wudong coal mine and its influence on the roadway stability were studied with comprehensive methods including geo-dynamic division, statistical analysis and numerical simulation, etc. The existing roadway support scheme was optimized. The results show that Wudong coal mine is mainly affected by Qingshuihezi fault, Wanyaogou fault, Baiyangnangou fault and other active faults. The statistical analysis of the time sequence characteristics of seismic activity and focal depth in Wudong Minefield shows that the geodynamic activity of Wudong minefield, especially its shallow part, is increasing year by year, and the energy of the shallow coal and rock mass is continuously accumulating; the underground in-situ stress measurement shows that the direction of the roadway is perpendicular to the maximum principal stress, which is unfavorable to the roadway stability. The numerical analysis shows that the surrounding rock stress increases with the mining of the upper panels in the same coal seam and contrarily it decreases with the mining of the adjacent panel at the same level. Affected by high level stress, surrounding rock lithology and weak surface of coal rock interface, the roof and floor of the roadway are damaged in a large range, and roof bolts and some anchor cables are in the plastic zone, resulting in insufficient anchoring. The energy accumulated in the roof will lead to dynamic disaster easily. On this basis, according to the current situation of roadway support, the methods and measures such as increasing the length of anchor bolt, increasing the pre-stress of anchor bolt, adopting full length anchoring, adjusting the angle of anchor cable, improving the surface protection materials, and using full length anchoring anchor bolt to reinforce the floor and bottom angle of roadway are proposed so as to,improve the stability of the roadway, and provide a useful reference for roadway support under similar conditions.