Gas extraction technology of kilometer hole in lower slice of thick and high-gas seams

Aiming at the problem of frequent gas overrun in working face during mining higher slice in thick and high-gas seams, on the basis of destruction extent and transport mechanisms of relieved gas in lower slice under the action of disturbance stress, gas extraction with kilometer hole in lower slice was studied with the background of working face 205 in Tingnan mine. Theoretical calculation and FLAC^3D numerical simulation indicate the maximum lower slice plastic failure depth is approximate 13 m, the optimal layout region of kilometer directional hole is 6~9 m below the floor of working face. Monitoring the gas extraction concentration of kilometer drilling in hole positions in the process of working face advancing shows kilometer hole with optimal extraction effect is between 6 m and 9 m, gas extraction concentration in drilling field continues to increase with working face advancing, and finally increases to approximately 68%. The study realized long-time and high concentration extraction in lower slice of thick and high-gas seams.