Mechanism of overburden breakage and prediction of pressurised racking in the face of integrated mining under the shallow buried close to the coal seam hollow area

Abstract The roof plate of the comprehensive mining face under the shallow buried close coal seam mining hollow area breaks at the coal wall, which is easy to cause the accident of cutting the roof and pressing the frame. Revealing the mechanism of breaking the overburden rock at the coal wall in the working face under the shallow buried close coal seam mining hollow area can prevent the press frame accident caused by the overburden articulated rock block breaking and destabilising at the coal wall. By constructing an analytical model of the mechanical analysis of the roof breakage of the lower coal seam under the influence of the stress of the basic roof breakage rock mass above the mining zone, Deriving the critical support strength of the braces for the fracture of the roof of the lower seam at the coal wall, Presenting an instability criterion for the articulated rock mass after fracture of the lower coal seam roof at the coal wall, Then, based on the critical support strength of the support and the instability criterion, we predicted the accident of the 4-coal group pressure frame in Shuangma 1 mine, The sensitivity of the critical support strength of the stent to each parameter was also analysed. The results show: The critical support strength of the brace increases linearly with the top rock load and exponentially with the angle of rotation of the top fractured rock mass. When the angle of rotation of the overlying fractured rock mass above the mining area reaches 42°, the basic top of the lower coal seam will fracture at the coal wall, but the articulated rock mass will not be destabilised; When the angle of rotation reaches 48°, the articulated rock block is destabilised and a press frame accident will occur. The critical support strength of the support has the maximum sensitivity to the rotation angle of the top fractured rock mass. This study can provide a theoretical basis for the prevention and control of press frame accidents in shallow buried close coal seam mining under similar conditions.