The seepage law of confined water in floor of backfilling working face in Hanxing Mining Area

In order to grasp the influence mechanism of mining parameters and filling parameters on the seepage failure of coal face floor over confined water, the research was conducted aiming at safe mining over confined water in Hanxing Mining Area. Based on the geological characteristics of coal seams in typical mines, the water-rock coupling generalized geological model of confined water mining was established and the mechanical behavior of stope floor was analyzed. According to the method of solving the propagation of concentrated load and uniformly distributed strip load on the semi-infinite plate and the superposition principle of elastic mechanics, the expression of stress distribution on the floor under the combined action of mining and water pressure were obtained. Then with the help of MATLAB calculation program, taking the mining conditions and measured data of the Hanxing Mining Area as an example, the distribution law of floor stress under the condition of water pressure or not was obtained. The mining stress isoline and the ordovician limestone water pressure isoline interwove and influenced each other, which aggravated the influence on floor deformation and failure. Furthermore, the floor stress distribution and principal stress difference distribution under the joint action of water and rock were obtained, and the failure mechanism of stope floor was revealed. Through the laboratory test of solid modification of granular gangue, the elastic modulus of modified filling material ranges from 30 to 50 MPa. The numerical simulation results showed that when the elastic modulus of filling body increased to 50 MPa, the acoustic emission events and cumulative release energy were significantly reduced. Meanwhile, a few cracks appear in the floor and were eventually controlled in a local range without instability expansion. The inhibition effect of filling body and the destruction effect of confined water reached a state of balance. The research results of this paper provide a forward-looking theoretical basis for the mining of coal seam spacing water within 30 m in Hanxing Mining Area.