Permeability of the Coal Seam Floor Rock Mass in a Deep Mine Based on In-situ Water Injection Tests

Abstract

In-situ water injection tests were carried out to study the hydraulic conductivity of the roadway floor strata in the Chengjiao coal mine. Reliable water pressure test data were obtained to assess the permeability of the floor’s rock mass. The initial water pressure of the intact rock mass was greater in the first water injection test, which indicated that its permeability was low. The water pressures increased when the test was repeated, which showed that cracks had propagated in the rock mass. The maximum hydraulic conductivity of the intact rock mass was obtained from different water injection tests and the results were compared with those of the Dongtan Mine in the Yanzhou coalfield, where the floor strata is geologically similar to the Chengjiao Mine’s. The test data verifies that the mine floor’s intact rock mass is very water-resistant. The risk of a water inrush can be judged by the numerical relationship between this resistance and the water pressure of the limestone aquifer. These results can be useful in preventing water inrush through the floor strata in other deep mines.