Research on the Height of Water Flowing Fractured Zone of Fully Mechanized Caving Mining in Extra-thick Coal Seam

Failure height of overlying rock mass in extra-thick coal seam conditions by fully mechanized caving mining affects the groundwater occurrence condition, which in turn, affects mine safety. Aiming at extra-thick coal seam conditions, this paper numerically stimulates the dynamic process of actual excavation. Results show that failure height increases with excavation volume, thereby increasing the location of abscission layer dropping along with increasing failure height. An abscission layer is formed along the depth, changing the condition of groundwater occurrence and exposing a hidden safety hazard in the field of continuous mining. The simulation results are in line with the fact by verification with drilling survey data.