Study on gas leakage law and hole sealing technology of gas drainage in layered drilling

When gas is pumped along the stratum, under the action of mine pressure, gas leakage is very easy to occur.In order to improve the effect of bedding boreholes, the axial and radial stress and fracture distribution characteristics of the drainage holes were analyzed through the stress distribution law of surrounding rock of roadway. Four types of air leaking channels were put forward: leakage of sealing material, leakage of coal around the borehole, leakage between sealing material and borehole wall, and leakage influenced by adjacent borehole. Based on the gas leakage channels, the principle of sealing the radial loosening ring of the solid borehole and the reasonable design of the length of the sealed hole should be obtained. According to the mechanism of air leakage and the principle of hole sealing, combined with the site conditions, the original polyurethane hole sealing process in Mengjin coal mine was investigated and optimized. It was concluded that the optimized sealing depth should be 20 m. Combined with the radial fracture range, the sealing technology of two blocks and one injection of SRS-Ⅱ high strength micro expansion rapid solidification sealing material was put forward. The industrial test was carried out in No.12030 transportation roadway. By comparing and analyzing the tracking and monitoring data before and after the optimization, it is concluded that the volume fraction of gas drainage after the optimization of hole sealing is 1.1～1.9 times of the original hole sealing process, and the pure quantity of gas drainage after the optimization is about 2.6 times of the original hole sealing process, and the original sealing process has a significant attenuation compared with the optimized sealing concentration and extraction pure volume. Therefore, the extraction effect of the optimized sealing technology has significantly improved compared with the original technology, which provides a reference for the same type of mine drainage and sealing.