Study on impermeability of floor strata in deep two-level area of suburban coal mine based on pressure permeability test

In order to study the impermeability of key rock strata of coal seam floor in suburban coal mines and evaluate the effect of water disaster treatment in working face, the method of on-site pressure permeability test was used to test the three rock strata of coal seam floor, and the measured data of on-site water injection pressure, water injection flow and water pressure of pressure tap were collected. The results show that the rock stratum in three rock strata of the coal seam floor has strong permeability resistance in the original state, there is no permeability phenomenon, and only the fracturing conduction of sandy mudstone leads to permeability conditions; comparing the initial and repeated water pressure processes of the three rock strata, it can be seen that the change trend of the water pressure of the monitoring hole is consistent with that of the water injection hole, but the permeability time of the repeated water pressure is significantly shorter than that of the initial water pressure, indicating that a certain permeability fracture is formed after the initial water pressure. The permeability coefficient and resistance capacity are used as indexes to quantitatively evaluate the permeability resistance of rock strata, and the maximum permeability coefficient is only 8.94×10^-6 cm/s, the results show that the test rock strata has the characteristics of micro permeability.