Theoretical Study on Stress Distinguishing Index of Gas Pressure Fully Released in Mining Seam

Abstract：According to the setting problems of the gas pressure fully released scope during the gas drainage and gas pressure releasing period in the high gassy and low permeability seam group, the fracture failure mechanics theory was applied to analyze the stress and strain relationship in the pressure releasing process of the seam and strata. The stress and pressure releasing ratio （ the stress value after the pressure released/the in-situ rock stress value） was proposed to be the index to distinguish the pressure fully released or in the seam. In combination with the deposit conditions of the high gas seam in Yangquan Mining Area, a study was conducted on the feasibility of the stress and pressure releasing ratio as the distinguishing index and the influence factors of the stress and pressure releasing ratio when the seam pressure fully released. The results showed that with the theoretical calculation of No. 3 seam in Yangquan No. 3 mine, the pressure releasing ratio when the pressure fully released was 0. 445 and could meet the actual data. The stress and pressure ratio when the pressure fully released would be related to the depth of the protected seam and the deeper depth, the smaller the pressure released ratio would be. When the depth was 100 -500 m, the variation of the stress and pressure released ratio would be high. And when the depth was over 500 m, the variation of the stress and pressure released ratio would be gently.