Effects of Valley and Slope Angles on Movement Laws of Water Flowing Fracture in Roof of Shallow Buried Extra Thick Coal Seam

Taking F6201 mining area of Buliangou Coal Mine as the engineering background, adopting the valley slope angle 60° model test and numerical analysis method to study the influence of the valley slope angle on the overlying strata movement and the development of water flowing fractured height in shallow-buried and extra-thick coal seams, the study shows that: the migration laws of roof overburden were controlled by the main sub-key strata: when the working face advanced to 112.5 m, five periodic collapses occurred in the sub-key layer 1, with a height of 15 m, which was consistent with the experience value of 16.5±2.2 m of the large mining height; when the working face advanced to 120 m, the sub-critical layer 2 collapsed, with a height of 37.5 m; at this time, the main key stratum and the sub-key stratum 3 collapsed synchronously, and the overall collapse height was 64.5 m; the water-spraying fractures developed on both sides of the valley, with height of 63 m and 81 m; the development height of water flowing fractured height increases with the increase of the slope angle of the valley, and was divided into two regions by the slope angles ≤30°and ≥30°; the development height of the water flowing fractured with a slope angle of 60° in the valley was 95 m, which was in agreement with the total height of 102 m.