Experimental research on measurement of permeability coefficient on the fault zone under coal mine in situ

Abstract

In order to measure permeability coefficient K of fault zone under coal mine quickly, the traditional borehole water pressure test method should be improved. After analyzing the principle of pressure water test in borehole, a new test method suit for borehole water pressure test under coal mine was proposed. In the new method, the time T was measured, and the calculating method was also changed from inverse algorithm to forward algorithm. According to the existing parameters and hydrogeologic conditions of fault zone, an empirical value of permeability coefficient Kc was set and then seven setting values were obtained. P-T figures of seven setting values were drawn by computer, and seven P-T figures were converted to K-T figures; the permeability coefficient could be read directly from the K-T figures. The new method was a fast experimental and calculating method to obtain permeability coefficient by borehole pressure water test on the fault zone in situ. The results were in good agreement with the low permeability coefficient of 7.5 × 10⁻⁸ and 8.0 × 10⁻⁸ m/s obtained by pressure water test in new borehole. And, the results were also in good agreement with the results of pumping test. This indicated that the pressure water test in the new borehole and the calculating method are accurate.