Test on Hard Top Coal Pre-Blasting and Weakening for High Gassy Fully Mechanized Top Coal Caving Mining Face

In order to improve the coal resource recovery rate of the fully mechanized top coal caving mining,a top coal pre-blasting and weakening test was conducted in No.40301 Fully Mechanized Top Coal Caving Mining Face of Dafosi Mine.Based on the special conditions of the hard and ultra thick seam in the gas rich accumulated area of the mine and base on the analysis on the hard top coal pre-blasting and weakening mechanism of the fully mechanized top coal caving mining face,the paper studied the gateway layout and the blasting technical parameters for the hard top coal pre-blasting and weakening of the high gassy fully mechanized top coal caving mining face and provided the site test plan.The test study showed that the ventilation status of the proposed mining gateway was good,the failures occurred in the top coal and the broken location was forwardly displaced,the failing angle of the top coal was obviously increased,the failing lump coal size of the top coal was obviously reduced,the coal caving speed was speed up and the strata behavior of the mining face were obviously relaxed.Also the test study showed that the gas in the seam could be certain released in advance.The top coal pre-blasting and weakening mode for the mining gateway layout along the dip direction could be the effective method to improve the mining recovery rate of the fully mechanized top coal caving mining face in a high gas,hard coal and ultra thick seam.