【正文】 n boreholes and wind emission in the floor roadway. The period of working face 21213 for which statistics were obtained was from , 2000 to Jan. 31, 2001, 365 days in accumulated amount of gas drainage by penetralion boreholes was and the amount by wind emission Mm3.The reserves of the protected layer were Mm3 and the total amount of gas drainage ,so that the rate of gas drainage reached 60%. The amount of gas inrush and amount of gas flowing into workout areas of the protective layer were not inccluded in our calculation, so that the actual rate of gas drainage was larger than the calculated value,.,a rate over 60%. Since the orieinal amount of eas of the C13 coal seam was 13m3/t. the restauai eas content was , given our calculations. Gas pressureWith the advancement of the working face, the pressure gauge value gradually decreased from , when the working face was 100 m away from the pressure measured hole。 drainage of pressure relief gas。河南理工大學(xué)萬方科技學(xué)院本科畢業(yè)設(shè)計外文資料與中文翻譯外文資料：Principle and engineering application of pressure relief gas drainage in low permeability outburst coal seamAbstract: With the increase in mining depth, the danger of coal and gas outbursts order to drain coal gas effectively and to eliminate the risk of coal and gas outbursts, we used a specific number of penetration boreholes for draining of pressure relief on the principle of overlying strata movement,deformation and pressure relief,a good effect of gas drainage was obtained. The practice in the Panyi coal mine has shown that, after mining the C11 coal seam as the protective layer,the relative expansion deformation value of the protected layer C13 reached %n, The nermeabilitv coefficient increased 2880 times, the gas drainage rate of the C13 coal seam increased to more than 60%, the amount of gas was reduced from to m3/t and the gas pressure declined from to MPa, which caused the danger the outbursts in the coal seams to be eliminated. The result was that we achieved a safe and highly efficient mining operation of the C13 coal seam.Keywords: protective layer mining。 technology principle。 engineering application1 IntroductionWith an increase in mining depth, the amount and pressure of gas increases, gas disasters are being more serious and several shallow and nonoutburst coal seams are gradually being outburst coal seams. Today, China has bee the country with the most serious coal and gas outburst disasters in the entire world. Globally, our frequency and intensity of outbursts are the most severe. In contrast, coal and gas outbursts coal mines had been stopped production in the USA, Australia, Russia and other countries. According to a statistical analysis by expert consultants in 2005, among 415 coal mines of the 45 major monitored state owned coal enterprises, 234 mines are high gas and outburst coal mines, accounting for % of the major coal mines and 142 mines are subjected to coal and gas outbursts, accounting for %.Usually, the permeability coefficient of outburst coal seams is low. For example, on average, this coefficient in the C13 coal seam of the Huainan ore area was only m2/(), which presented great difficulties in predrainage of gas and in gas control to prevent outbursts in coal seams. Based on the current condition of coal seams in the Panyi coal mine, we adopted a protective layer in our mining technology to drain pressure relief gas from protected seams,using RC net penetration boreholes in floor roadways, effectively reducing its gas content, pletely eliminating the danger of outbursts and achieved safe and highly efficient mining conditions.2 General situation of test areaThe Panyi coal mine is a large mine designed for 3Mt production capacity. The C13 coal seam is one of its primary and most productive coal seams, which contained a large amount of gas under high large number of outburst accidents have formerly occurred during mining, including a major gas explosion, so control over coal gas was very urgent before we could exploit this coal seam.The test area was located between the East1 and East2 mining areas, with the B 11 coal seam as a protective layer.