Study On Coal Layer Anti-reflection Technology Of Low Gas Permeability Coal Seam In Pan Yidong Coal Mine

This article mainly study the problem of the gas drainage in low permeability coal seam in Pan Yidong coal mine. It researched about borehole gas drainage strengthening antireflection technology by cutting hole through the study of mechanism of coal and gas outburst, gas flow pattern around the borehole, pre-drainage gas technology, combined with the computer numerical simulation technology and industrial test in Pan Yidong coal mine. First of all, it lays the theoretical basis by studying of borehole gas flow rule, borehole drainage to prevent gas and coal outburst mechanism. Then, we tested the gas basic parameters of coal-bed of11-2, build a geometric model of the borehole gas drainage, investigated the change of the pressure around the original drilling and cutting hole drilling by FLUENT numerical simulation and analysised the influence radius of the drilling before and after cutting hole. Conclusion:the original borehole effect radius is2m and the cutting hole influence range reached3m. It tested the effective drainage radius of borehole before and after cutting hole reaming by the method of tracer gas of actual conditions. The measured results were according to the numerical simulation results. According to the borehole effective drainage radius, the optimization design of borehole spacing and drilling field arrangement is carried out. Though calculating:the arrangement of11-2Grossmeasures boreholes in coal seam is according to the6m*6m grids. Last of all,it studied about the cutting hole reaming antireflection effect and drainage effect of the Pan Yidong coal mine.Though a cutting hole of borehole gas drainage, the gas pressure, gas content, the largest drilling cutting weight Smax, coal firmness coefficient f,â–³h2, coal initial velocity of gasâ–³p during the tunnel excavation process in the area of influence shall not exceed the "coal and gas outburst prevention provisions stipulated by the prominent" index critical value; the outburst eliminating effect is good, thereby successfully protect the coal lane tunneling, guarantee safe production of the coal mine.