Practice on Gas Control Technology of Floor Drainage Gateway with Two Uses

In order to solve the low utilization ratio of the floor drainage gateway in the gas drainage of the protective coal seam mining, the low control effect of the gas concentration in the coal mining face and the high layout cost of the gateway and drilling site, in combination with the geological condition of Guqiao Mine, the locat ion of the floor drainage gateway and the layout of the gas drainage boreholes were rationally determined. The gas drainage method in the floor drainage gateway with two uses was applied to drainage the pressure released gas from the above protected seam and to drainage the gas in goaf and upper corner after the mining operation in the underlying protective coal seam. After the gas drainage operation completed in the floor drainage gateway, the maximum and minimum residual gas pressure in t he protected coal seam after the pre- drainage was 0.49 and 0.21 MPa individually. The average pressure was 0.38 MPa and was much lower than the in- situ seam g as pressure of 0.67 MPa. With the gas drainage operation conducted, the gas volume fraction in the air returning was controlled at about 0.17%, the gas volume fracti on in the upper corner was below 0.7%, the gas drainage volume fraction was about 30% and the gas drainage quantity was above 50 m3/ min.