The Aging Research On Characteristics Of Gas Drainage Radius In Bedding Drilling On Wulunshan Coal Mine

Gas disaster is one of the major natural disasters in coal mine safety production, at present our country in the absence of protective layer mining of low permeability seam, often used in underground drilling on coal seam gas pre pumping. Borehole gas drainage is one of the most important factors is the reasonable hole spacing, and the cloth hole spacing depends on the drainage radius of borehole, the drainage radius and subject to the restriction of various factors. Therefore, the research of pre drilled the aging characteristics of influencing factors of gas pumping has important significance.The Wulunshan coal mine 8 coal seam gas as test object, basic parameters are as follows:8 the original coal gas pressure is 1.02MPa, the average 12.50m3/t of coal seam gas content, permeability coefficient of coal seam is 0.1024 m2/(MPa2·d). Of drainage borehole in coal body around should force change and the law of gas flow, draw borehole pressure relief range and the size of the hole size was linear positive correlation, but for the special coal seam, such as outburst coal seam is, the drilling is too general to lead to hole collapse, and even lead to coal and gas outburst. With the five round of the basic parameters of coal mine by using COMSOL software on the influence factors of drainage radius are simulated, the extended drainage time can be as much as possible out of gas in the coal seam, but the existing extraction time limit, if more than the limit of extraction time, the effect will be greatly reduced, the gas drainage; drainage borehole the drainage radius increased with the increase of the hole diameter increased, but the pore size increased to a certain extent, drainage radius and drainage efficiency increase is far less than the hole diameter increases, the hole diameter change on drainage time has no effect; the original coal gas pressure is, the smaller the radius of mining drainage borehole, the seam gas content increases, the corresponding drilling drainage quantity is larger; the original coal seam permeability of drilling for gas pre drainage effect is very significant, the greater the initial permeability, borehole The bigger the influence of mining gas, the better the effect, the more slow down the gas drainage, the longer the limit of pumping time. Through the simulation results, combined with field practice. In 1805 Wulunshan coal mine coal working face using content method and the flow field measured borehole gas pre drainage drainage radius, through the analysis and comparison of two methods, it is concluded that the limit of Wulunshan coal mine coal extraction time was 150 d,reasonably dispatched spacing is 2m. After pumping mining area of effect, the indicators were lower than that of anti process specified critical value. It is proved that the effectiveness of coal seam gas pre drainage, provides the guarantee for the safe production in mining area.