| Gas disasters is the biggest threat to safe production in coal mine of our country and gas drainage is the fundamental measures against gas disasters and accidents.The gas drainage has controlled the gas outburst and the gas overrun, but there is not reasonable certain to pre- draining time,In order to solve this problem, according to the different drillhole pattern, confirming reasonable pre-draining time has important significance to improve gas drainage effect, avoid blind drainage, realize the high yield and efficiency. On the basis of taking samples,this paper has confirmed the marginal value of eliminating outburst about using the index to predict gas outburst in NO.3 seam of YameiDaning coalmine through laboratory simulation,and based on drillhole parameters, the relationship between quantity of drainage and time,the method of calculating practical pre-draining rate of Directional Level Long Drilling has been determined, on this basis, combining with the influence factors of pre-draining rate,the evaluation model of reasonable pre-draining time has been builded and the reasonable pre-draining time of Directional Level Long Drilling in coal face has been calculated, in the end,the paper probes into the reasonable drillhole parameters in coal face.On the basis of analysising geological evolution and geological structure characteristics,the paper introduces the regional integrated measures to against outburst,and analyzes the feasibility which choices the bedding pre-draining as regional measures in the Daning coalmine. Combined with different drillhole parameter and quantity of drainage in different time,this paper investigates the drainage effect of Directional Level Long Drilling under points different deepness groups and obtains the relationship between pre-draining rate and time,.through the analysising the effect of different length of Directive Horizontal Long, confirms the reasonable length of the drillhole.
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