## 1 Introduction
In the mining of large dip angle coal seam, as the working face advances, the stress arch shell continues to expand to the rear of the open-off cut, the coal wall in front of the working face, the coal wall of the return air roadway and the transportation roadway and the upper rock layer, and the degree of asymmetry increases. Along the direction of the coal seam, the flat zero of the stress supply gradually increases; along the tendency of the coal seam, the flat zero of the stress supply decreases, and the position of the maximum height of the stress supply continues to shift to the side of the return air roadway [20; 21]. With the transfer of coal mining from shallow to deep, the deformation and failure characteristics of overlying strata in stope have also changed significantly. After the mining of deep rock strata, a large amount of energy produced by stress release is coupled with the splitting reaction caused by high-ground stress and overburden unloading, and the zonal disintegration phenomenon occurs in the deep overburden. The overburden fracture zone mainly occurs in the low-stress zone of the stress shell, and the zonal disintegration characteristics are closely related to the time-space effect [22; 23]. In the process of stope advancing, the coal and rock mass in front of the working face is divided into an elastic zone, plastic zone, and elastic-plastic zone, which correspond to the original stress zone, peak stress zone, and stress reduction zone of mining abutment pressure respectively. When the overlying strata are regarded as the statically indeterminate beam with two fixed ends under uniform load, the deformation can be divided into the elastic stage, plastic deformation stage, elastic limit stage, and plastic flow mechanism stage. The bending moment in the elastic stage increases proportionally with the increase of load q, and the position of the zero bending moment section does not change. The position of the zero bending moment section in the latter three stages changes continuously with the increase of load \(q\). The bending moment no longer increases proportionally with the increase of load \(q\)[24]. When the bending moment exceeds the limit value, the direct roof strata with low bearing capacity in the shallow part of the roof have plastic damage such as deflection, fracture, and collapse in a short time. The caving rock mass accumulates in the goat, and the roof-bearing area of the stope moves up to the high-strength strata. At this time, the main roof can be regarded as an elastic plate. As the working face advances, the load of the overlying strata gradually increases. The roof fracture first begins near the center of the long side, then turns to the center of the short side, and finally turns to the center of the plate surface. The failure of the long and short sides of the roof forms a plane 'O' type fracture form crack. When the roof fracture failure is completely over, the space 'O' type crack formed by the failure of the long and short sides of the upper surface of the roof and the space 'X' type crack formed by the bottom surface of the roof together form the space 'O-X' type fracture form of the roof fracture [25; 26]. With the increase in mining progress, the blocks at different positions of the overlying strata in the goaf continue to rupture, and the number of ruptured blocks continues to increase. The 'basic roof' that plays a bearing role moves upward along the vertical direction with the change of the semi-elliptical stress field. In the actual process of coal mining, the movement law of overlying strata is not only related to the mechanical properties of overlying strata but also closely related to the foundation coefficient of its underlying support body.