Staging Gas Drainage Technology in Goaf During Periodic Caving of High-level Tunnel

For the problems that goaf gas emission rate accounted for 82% of the working surface emission rate, serious gas exceeding at the upper corner and support gap of fully mechanized caving mining of Tashan Mine with large mining height, based on variation laws of gas storage in goaf, high-level tunnel in caving zone was arranged, which realized "one roadway two functions" gas control technology in goaf by periodic caving. Through the experiment, high-level tunnel is arranged in 2^# coal seam, which is used as special gas discharge laneway to transform working face ventilation system from the "U" type to "U+I" type in initial period of mining. The gas emission rate of high-level tunnel gradually increased to 30 m³/ min, and the gas drainage amount of return air roadway fell to 5 m³/ min from the initial 23 m³/min. The high-level tunnel was closed as large diameter drainage pipe to extract gas by negative pressure in middle and late period of mining. The gas emission rate of high-level tunnel increased to 40 m³/min, which increased by 33% compared with initial period of mining. The gas of upper corner at working face was controlled below 0.6% during mining, which controlled goaf gas effectively.