河南理工大学万方科技学院本科毕业设计外文资料与中文翻译外文资料：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 increases.In 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 gas.Based 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 2.63%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 13.0 to 5.2 m3/t and the gas pressure declined from 4.4 to 0.4 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; drainage of pressure relief gas; engineering application1 IntroductionWith an increase in mining depth, the amount and pressure of gas increases, gas disasters are becoming more serious and several shallow and non-outburst coal seams are gradually becoming outburst coal seams. Today, China has become 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 56.4% of the major coal mines and 142 mines are subjected to coal and gas outbursts, accounting for 34.2%.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 0.011 m2/(MPa2.d), which presented great difficulties in pre-drainage 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, completely 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 pressure.A 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 East-1 and East-2 mining areas, with the B 11 coal seam as a protective layer. We planned to combine mining the 21511 working face in East-1 and the 23521 in East-2 and called the combination 23521 instead The strike of the face is 1640 m and the trend 190 m.The thickness of the coal seam is between 1.52.4 m,2.0 m on average and the dip angle 60-130, 90 on average. The amount of gas of the B11 coal seam is 4-7.5m3/t and it is a non-outourst coat seam.The coal seam is stable and its geological structure simple.Fully mechanized coal mining technology had been adopted for the working face, designed for 2000 t/d.The C13 coal seam is a protected layer, located 70m above the B11 coal seam. The corresponding test working face of the protected layer consists of the 21213 working face in East-1 and the 23223 in East-2 (called 21213/23223 combined). The strike is 1680 m (two faces in all) and the trend is 160 m.The coal seam is 5.576.25 m thick, 6.0 m on average,the dip angle 60130 and 90 on average. The original measured gas pressure was 4.4 MPa, the amount of gas 13.0m3/t and the original permeability coefficient only 0.011 m2/(MPa2.d). The coal seam was also stable and its geological structure simple. By draining the pressure relief gas, the danger of outbursts in the C13 coal seam could be eliminated and the amount of gas was effectively reduced.A comprehensive，mechanized cover caving coal mining technology been adopted for this working face, which was signed for 5000 t/d.3 Drainage principle of pressure relief gasDraining of pressure relief gas is referred to as protective layer mining technology. When we mine coal seams in outburst coal mines, we should first mine the non-outburst or low risk outburst coal seams as prote