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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 protective layers, where the outburst coal seam is then called the protected layer. With protective layer mining, the coal and rock mass among the roof and floor moves and deforms within certain limits,which causes stress changing. Fracture fields are redistributed, ground stress is reduced, the coal seam expands, the coal seam permeability coefficient increases and drainage condition are created for pressure relief gas in the protected coal seams. In the case of the Panyi mine, we drilled penetration boreholes or carried out surface well drilling to drain the pressure relief gas, which caused the amount of gas and pressure to decrease significantly and the coal mass turned hard. Naturally. eas pressure reduced to below 0.5MPa, the amount of gas reauced to below a 6m3/t and the coal consistency coefficient rose 48%-100%.At the end, the danger of outbursts was completely eliminated from the protected layers and conditions for safe and highly efficient mining had been achieved. Drainage indices of pressure relief gas in the different ore areas are shown in Table 1.4 Drainage methods of pressure relief gasDrainage methods of pressure relief gas consist largely of draining gas from the protected layers affected by mining. The space between the protective working faces 23521 and 21213/23223 was about 70 m, which is really a long distance below the protective layer mining. We have often used surface well drilling and upper penetration boreholes located in floor roadways to drain pressure relief gas from the underside of the protective mining layer. Surface well drilling is unreliable and we often used penetration boreholes. The design of penetration boreholes includes the construction of a floor roadway, a suction drilling field and upper penetration boreholesAll construction activities should be completed before starting mining the protective layer and we should ensure that the pressure relief gas has been drained simultaneously with mining the protective layer.4.1 Design and construction of the floor roadwayBased on the occurrence of coal strata and concrete geologic conditions, the floor roadway was located 10-20 m below the C13 coal seam in a good lithology rock bed and 4656 m from the protective layer.On the one hand, this position assured safe excavation, avoided gas inrush from the C13 coal seam and prevented the excavation of another coal seam by mistake. On the other hand, this location did not affect the mining of the B11 coal seam and assured normal functions for gas draining. The floor roadway was located in the middle of the working face of the protected layer on the strike where,in principle,one should insist on avoiding forming down holes.The proportion of the section of the floor roadway was designed for 6 m24.2 Design and construction of the suction drilling fieldAt working face 23223, 51 fields had been constructed west forward and away from the stopping line in the floor roadway under the C13 coal seam. In the pressure relief area, a field was set every 40 m, so the pressure relief area of face 21213/23223 in the protected layer needed 39 fields in all. According to the pressure relief angle, non pressure relief areas were present in the protected layer, with a field every 10 m, so that the non pressure relief areas of face 23223 in the protected layer needed only three fields and nine in face 21213. The drilling field was perpendicular to the floor roadway,with a length of 5m and a net section proportion of 6.16 m2 Bolt-shotcrete support technology had been adopted.4.3 Design and construction of upper penetration boreholesEvery drilling field had 4 holes set on the strike in the pressure relief area. The space between holes was 40 m, which was oriented on the middle of the thick-surface of the coal seam. The position of the hole opening was located at the top of the drilling field and the final hole position ended 0.5 m into the roof of the C13 coal seam. Its design is shown in Fig.1. The total length of the draining holes was 8879 m,of which 1460 m was drilled through the C13 coal seam. The space between holes was 10 m in the non pressure relief area.5 Pressure relief levelAfter mining the protective layer, this layer moved and deformed, which caused ground stress to reduce,the permeability coefficient to increase and pressure relief occurred. Pressure relief levels are related to the space of the layer, rock lithology, mining height and so on. The levels are higher and the pressure relief effect is better in the protected layer. The change of ground stress can visibly reflect the pressure relief level, but the stress is hard to measure in the field, so we adopted the extent of coal deformation and the coal seam permeability coefficient to reflect the level indirectly.5.1 Relative deformationWe adopted a base point method to investigate the deformation of the C13 coal seam. To start, we drilled a deep hole, and then installed test points in the roof and floor of the C13 coal seam, where the deformation was determined by the relative displacement of the two test points. The measured results are shown in Fig.2. We can see that, during mining of the B11 coal seam, the C13 coal seam was first compressed, and then expanded, the maximum compression deformation was 27 mm and the maximum expansion deformation 210.44 mm, so that the maximum relative compression deformation was 0.337%, and the maximum relative expanding deformation 2.63%. The bigger the expansion deformation, the better the effect of pressure relief.5.2 Variation of permeability coefficientThe orieinal coal seam nermeabilitv coefficient was only 0.011m2/(MPa2.d).After mining the B11 coal seam, the pressure was relieved from the C13 coal seam and the permeability coefficient clearly increased. By using the amounts of residual gas and the borehole gas inrush, we calculated that the permeability coefficient had increased to 32.687 m2(MPa2.d), an increase of almost 2880 times, which indicated that the C13 coal seam was now in the condition where gas has been drained.6 Drainage effect of pressure relief gas6.1 Amount and rate of gas drainage1) Analysis of drainage of pressure relief gasWhen the protective working face advanced 40 m over the suction drilling field, the amount of gas drained rapidly increased. Fig.3 shows the variation in the amount of gas drainage vs.time in the drilling yard of the Huainan coal mine. The original 20 days was the period of increased gas drainage, enhanced pressure releasing activity and the amount of gas drainage increased. The period between 20-80 days was the active period of gas drainage, the pressure release activity became regular and permeability reached a maximum. Gas drainage was regular and the amount of gas drained from a single hole was over 1.0 m3/min. After day 80 the attenuation period set in, where the coal seam became gradually compacted, permeability reduced, the residual pressure became small and the amount of gas drainage reduced exponentially. According to this research, a highly effective drainage period was 2 months, the length of the affected area was 160 m and the number of active drainage holes was 16. On average, the amount of gas drained from a single hole was about 1.0 m3/min Aftter 4 months of continuous gas drainage ,the rate of gas drainage reached over 60%.2) Total amount of gas drainage and amount of residual gasThe total amount of gas drainage includes the amount drained from penetration boreholes and wind emission in the floor roadway. The period of working face 21213 for which statistics were obtained was from Feb.1, 2000 to Jan. 31, 2001, 365 days in all.The accumulated amount of gas drainage by penetralion boreholes was 7.99Mm3 and the amount by wind emission 0.74 Mm3.The reserves of the protected layer were 14.68 Mm3 and the total amount of gas drainage 8.73Mm3,so that the rate of gas drainage reached 60%. The amount of gas inrush and amount of gas flowing into work-out 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,i.e.,a rate over 60%. Since the orieinal amount of eas of the C13 coal seam was 13m3/t. the restauai eas content was 5.2m3/t, given our calculations.6.2 Gas pressureWith the advancement of the working face, the pressure gauge value gradually decreased from 4.4MPa, when the working face was 100 m away from the pressure measured hole; when 80 m away, the pressure sharply decreased, and at 62 m the pressure gauge finger pointed to zero. When the protective working face advanced 400m past the pressure measured hole, the pressure value increased from zero to 0.4 MPa and remained stable, which indicated that the residual gas pressure was 0.4MPa.6.3 Outburst danger eliminated analysis of the protected layerThe amount of gas in the protected layer is decreased by draining the pressure relief gas.The amount of residual as of the C13 coal seam was reduced to 5.2 and the residual declined to 0.4 MPa. The amount of gas pressure values were lower than the critical value, which was 8m3/t for the amount gas and 0.74MPa (pressure gauge) for gas pressure.All this shows is that C13 coal seam had changed from a high gas and outburst coal seam to a low non-outburst coal and C13 became a safe and highly effective coal seam where mining conditions became considerably better, as proven by its current mining practice.7 Conclusions1) With the advancement of a working face, coal and rock masses among the roof and floor move and become deformed within certain limits, ground stress is reduced, coal seams expand and the coal seam permeability coefficient increases in outburst coal seams. After mining of the Bllcoal seam, the maximum relative compression deformation of the C13 coal seam was 0.337% and the maximum relative expansion deformation 2.63%. The permeability coefficient increased almost 2880 times and favourable conditions for drainage of pressure relief gas were obtained in the protected coal seam C13.2) The most effective gas drainage method is the use of upper RC net penetration boreholes in the floor roadway. For an optimum pressure relief level, the space between holes should be 40 m in the pressure relief area and 10m in the non pressure relief area.3) After gas draining of the C13 coal seam,the amount of gas in the C13 coal seam effectively decreased，from 13.0m3/t to 5.2m3/t and the rate of gas drainage reached above 60%. The gas pressure was reduced from 4.4MPa to 0.4MPa. In the end, the danger of outbursts had been completely eliminated in the protected layer and safe and highly efficient mining conditions had been achieved.AcknowledgementsThe authors are grateful to the National Basic Research Program of China, and the National Natural Science Foundation of China for their support Science Foundation of China for their support.1 Cheng Y P, Yu Q X. Developmet of regional gas control technology for Chinese coalmines. Journal of Mining and Safety Engineering, 2007, 24(4): 383-390. (In Chinese).2 Cheng Y P, Yu Q X. Application of safe and high-efficient exploitation system of coal and gas in coal seams.Journal of China University of Mining & Technology,2003, 32(5): 471-475. (In Chinese).3 Wang H F, Cheng Y P, Yu Q X, Zhou Z Y, Zhou H X,Liu H Y Research on the amount of safe mineable coal in mines susceptible to coal and gas outburst Journal of China University of Mining & Technology, 2008, 37(2):236-240. (In Chinese).4 Cheng Y P, Yu Q X, Yuan L, Li P, Liu Y Q, Tong Y F.Experimental research of safe and high-efficient exploitation of coal and pressure relief gas in long distance.Journal of China University of Mining & Technology,2004, 33(2): 132-136. (In Chinese).5 State Administration of Coal Mine Safety. Coal Mine Safety Regulation. Beijing: China Coal Industry Publishing House, 2007: 113-119.6 Yu Q X. The Prevention and Control of Gas in Coal Mines. Xuzhou: China University of Mining and Technology Press, 1992. (In Chinese)7 Liu L. Relief gas drainage technology during distant under-protect seam reining. Mining Safety & Environmental Protection, 2007, 34(6): 45-47. (In Chinese).8 Wang L, Cheng Y P, Li F R, Wang H F, Liu H B. Fracture evolution and pressure relief gas drainage from distant protected coal seams under an extremely thick key stratum. Journal of China University of Mining & Technology, 2008, 18(2): 182-186.9 State Administration of Coal Mine Safety. Gas Drainage Basic Index in Coal Mine (AQ 1026-2006), 2006. (In Chinese)中文翻译： 低透气性煤层瓦斯突出卸压原理及工程运用摘要：随着开采深度的增加，瓦斯突出危险也随之增加。为了能够有效地释放瓦斯压力，消除瓦斯突出的风险，我们使用一个特定数量的渗透钻孔抽瓦斯。由于过度的岩层运动，变形减压原则获得一个好的气体引流效果。潘一矿实践表明，作为保护层开采的C1l煤层,被保护层的相对扩张变形值C13达到2.63%!渗透系数增加了2880倍,C13煤层瓦斯抽放率增加到60%以上，气体量从13.0m3/t降低到5.2m3/t，气体压力从4.4MPa下降到0.4MPa，这使得在煤矿中造成突出的危险消除。这就使我们在C13煤层实现了一个安全、高效的采煤作业环境。关键词：保护层 技术原理 引流减压瓦斯 工程应用1引言 随着开采深度的增加,瓦斯的含量量和压力增加,瓦斯灾难变得更加严重些，一些浅和不爆发的煤层也逐渐变成突出煤层。现在,中国已成为全世界煤与瓦斯突出灾害最严重的国家，在全球范围内，我们国家瓦斯突出的强度是最严重的。相比之下，在美国、澳洲、俄罗斯、和其他国家煤和瓦斯爆炸已经不再出现了。根据2005年专家顾问的统计分析数据，在415个煤矿中有45个重大的国有控制煤矿企业，234个高瓦斯矿，占主要煤矿的56.4%，142个煤矿有瓦斯突出，占34.2。通常,煤层的低渗透系数低，例如,平均来说,在淮南地区的开采的煤层中C13的系数只有0.011m2/(MPa2.d)，它目前最大的困难在提前排出瓦斯控制在煤层中发生瓦斯突出。基于当前潘一煤矿的煤层状况，在开采中我们采用了开采保护层开采技术进而从保护层释放瓦斯,在底板使用钢筋混泥土网状渗透钻孔,有效地降低其瓦斯的含量,完全消除突出的危险,取得了安全、高效的开采环境。2 测试区概况潘一煤矿是一个有3Mt生产能力的的大型煤矿。C13煤层是它主要开采煤层，它包含着高压下大量的天然气。大量的突出事故发生在开采中,包括一个重大瓦斯爆炸事故,所以在开采这个煤层之前，控制瓦斯含量非常重要。 测试区位于东1和东2矿区，B11煤层作为保护层。我们计划结合开采工作面东1矿区21511和在东2矿区23521。开采的的煤层深度是190m到1600m，煤层厚度是平均1.5米2.4米，倾角平均613。B11煤层是47.5m/t,它是非突出煤层，由于煤层稳定且其地质结构简单，采用综采日产量2000t。C13煤层是一个保护层，在B11煤层之上间距70米。相应测试开采层的保护护层由东1矿区的21213工作面和东2矿区（21213工作面/23223工作面的总和）构成,开采煤层是深度从160m到1600m包含两层煤。煤层平均有557625 m厚，倾角平均69。原始瓦斯压力是4.4MPa,瓦斯含量是13.0m/ t，原始煤层渗透系数仅为0.01l/(MPa.d)煤层也稳定且其地质结构简单。通过释放瓦斯压力,在C13煤层突出的危险可以被消除并且瓦斯的数量可以有效地减少，采用综采日产量5000t。3 瓦斯压力原则瓦斯压力释放被作为一种被保护层开采技术。当我们在易发生瓦斯爆炸的煤矿开采时，我们首先把不发生突出或着低煤层突出危险的煤层作为保护层，那些突出煤层的地方被称为被保护层。随着保护层的开采，顶部和底部的煤层和岩石层移动并在一定范围内变形，这导致压力改变。易碎层重新分配，地面压力减小，煤层扩大，煤层透气性系数增加，从而使在保护层排泄条件有利于缓解瓦斯压力。在潘一煤矿的例子中，我们用钻孔或进行透气钻孔引流减少瓦斯压力和含量,这造成的瓦斯含量和压力显著降低并使煤炭质量变硬。当然，瓦斯压力减少到低于0.5MPa.，气体量减少到低于6m/t，煤炭的浓度系上涨48%100%。最终，突出的危险完全被排除在被保护层，安全高效率的开采条件得以实现。在不同岩层排放瓦斯的指数领域如表1所示地名层空间(m)相对扩大变形透气系数增加的倍数抽放率瓦斯含量瓦斯压力采煤点淮南潘一矿702.63288060.05.20.4下保护层沈阳红领矿160.72101077.55.060.35上保护层淮南谢一矿190.468.04.30.5上保护层阳泉三矿1250.78468.85.76下保护层4瓦斯压力的排放途径瓦斯压力的排放途径包含在开采过程中大量从保护层释放出来的瓦斯。保护层开采的是23521工作面和21213/23223工作面间距有70m，这是低于保护层开采的距离。我们经常使用的地表打钻和巷道钻孔，通过钻孔排出瓦斯使保护层的下部卸压。地面打钻是不可靠的，我们经常使用的穿层钻孔，穿层钻孔的设计包括岩层大巷的建设，钻场和穿层钻孔。所有准备工作应在开采被保护层之前完成,随之开采被保护层时，我们应该确保瓦斯含量已经排到临界值以下。4.1巷道的设计与施工基于煤层条件和具体的地质条件，巷道在C13煤层以下1020米较好的岩层里布置或在C13煤层以上4656米较好的岩层。一方面，这个位置要保证安全，避免气体从C13煤层涌出,防止另一个煤层开挖的错误。另一方面，这个位置并不影响B11煤层的开采保证正常的瓦斯抽放的。岩层巷道沿走向位于作业场所的中间保护层，原则上,我们应该坚持避免形成地下洞，巷道的断面是6m2。4.2钻场抽放的设计与构建在23223工作面,51钻场已经建成，远离C13煤层巷道禁止线，在减压区，每一个区段的设置是40m。所以减压区的表面为21213/23223在防护层总共需要39个钻场。根据减压角度、非减压区目前在被保
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