Study On The Drilling Distance And Negative Pressure Of 2601 Working Face Gas Pre-drainage In Zhangcun Coal Mine

With the mining depth and intensity of comprehensive mechanized cover caving coal increasing,the gas emission is growing and the risk of coal and gas outburst is rising.Gas has become the main factor that restricts the safe production and high production efficiency.For high-gas mine,the use of pre-drainage gas drilling can effectively reduce the coal seam gas content and ensure the safe mining of working face.The distance and the negative pressure are the two most important parameters for pre-drainage gas drilling,by the rational arrangement of the pre-drainage gas drilling distance and the negative pressure of this coal seam,it can not only ensure the safe mining,shorten the drainage period,but also save the cost.In this paper,the pre-drainage drilling of coal seam in Zhangcun coal mine is taken as an example,the rational arrangement of the pre-drainage gas drilling distance and the negative pressure are studied.This paper adopts the research method of theoretical analysis,numerical simulation and field application,the gas basic parameters of 2601 working face is measured and the Coal seam gas content which should be solved is analyzed.By studying the phenomenon of non-Darcy seepage in low-velocity seepage of high-gas seam,Darcy 's law considering threshold pressure gradient is obtained,and the threshold pressure gradient is measured.By studying the coupling effect between the gas migration and the deformation of the coal and rock,the gas flow control equation considering the threshold pressure gradient,dynamic permeability and porosity is deduced;the coal and rock deformation control equation considering the pore pressure and the expansion stress after adsorbing is deduced;the fluid-solid coupling model with threshold pressure gradient is constructed and the gas extraction effect with different spacing and negative pressure is simulated.From the point of view of saving the cost of mining,combined with the coal seam gas content to be solved by drilling pre-draining,the extraction effect of different draining parameters of 2601 working face is studied.What the results show is that:in the scope of drilling distance between 2.5 and 3m,draining time within 360d,when the spacing is 2.5m,the negative pressure is 30KPa,while the spacing is 3m,the negative pressure is 40KPa.According to the numerical simulation results,the design of the drilling distance is 2.5m,the draining equipment is selected as the ground pump station model BEC72 water ring vacuum pump,the application of the borehole spacing in the 1601 working face of Zhangcun Mine is proceeding.The draining effect is ideal that 1.18m3/t of seam gas content is draining out according to the analysis of draining data in the ventilation passage.