Simulation Study on Design Parameters and Position Determination of High Level Gas Drainage Gateway

A design with two air income and two air returning was applied to the gateways of coal mining face in Changcun Mine,the coal lost was high and the gas drainage efficiency was low.The FLAC3D software was applied to simulate the failure law of the overburden strata during the coal mining process.K8 stratum with a distance of 31 m above the roof of No.3 seam was determined as a key stratum.The UDEC software was applied to simulate the crack development and distribution law of the overburden strata during the coal mining process and the crack development zone along strike direction of the coal mining face was at 5~48 m beyond the open-off cut.The vertical crack development zone was at 21~31 m vertically above the seam roof.The width of the breaking zone in the goaf above the open-off cut was about 40 m and width of the fractured zone above coal mining face was about 48 m.The width of the crack development zone at the two side of the gateway sidewalls was less than 40 m.According to the measured results of the crack zone in a neighboring coal mining face S-39 of No.2103 coal mining face.The numerical simulation results was consistent with the test results that overlying strata fissure development zone locates in the 36 m range of roof.According to the results of numerical simulation and test results,the parameters of high level gas drainage gateway was designed that the distance between horizontal layer and air return way was 30~45 m,the distance between vertical horizon and coal seam roof was 27 m.