Study on Numerical Simulation of Gas Pre-Drainage for Fully Mechanized Top Coal Caving Mining Face

With the analysis on the flow basic law of the seam gas deposit, a simulation study was conduced on the variation of the gas basic parameters as well a s the variation of the gas pressure field and velocity field around the borehole under the gas drainage with different negative pressures in No.5305 fully mechanized top coal caving mining face in Chengzhuang Mine.A gas drainage trial was conducted in the mining site.The gas drainage effect showed that a regional borehole gas draina ge was conducted in the fully mechanized top coal caving mining face in a seam with a in-situ gas related content higher than 8 m3/t.The effective drainage radius of th e borehole was 23 m and the layout space of the drainage boreholes was 46 m.After over 8 month gas drainage, the average borehole drilling length per ton coal was 0 ver 0.05 m and the gas drainage rate was 40%50%.