Failure mechanism of coal seam floor with concealed structure and evolution law of confined water seepage

Confined water inrush disasters occur frequently in Hanxing mining area in China. In order to deal with mine water inrush disasters effectively, it is necessary to master the point and speed of water inrush from floor. According to the water inrush problem of mine with confined water in Hanxing mining area, a generalized model of mined space with concealed water-bearing structures was established from perspective of combined action of mining disturbance and confined water. The calculation results showed that, under the geological conditions of Hanxing mining area, the floor stress disturbance range was within 60 m after mining, and the main influence range of floor water pressure was 40 m above the interface of ordovician limestone. Furthermore, based on a simplified plane strain mechanical model of crack tip, the variation law of permeability coefficient of cracks along the path under different stress field of floor was obtained. The permeability coefficient of the cracks increased non-linearly along the direction of seepage, and increased sharply within 30 m of the working face floor. The closer it was to the stope, the smaller the seepage velocity was. According to the distribution law of principal stress difference, the conclusion of floor damage ahead working face and water inrush lagging working face can be drawn. The variation law of confined water permeability coefficient and permeability velocity obtained in this paper can provide theoretical basis for disaster control.