煤矿瓦斯预防治理中英文对照外文翻译文献

煤矿瓦斯预防治理中英文对照外文翻译文献(文档含英文原文和中文翻译)
翻译:
西班牙Riosa–Olloniego煤矿瓦斯预防和治理
摘要
矿井中一直控制存在不同的气体在采矿环境。

这些气体中，甲烷是最重要的，他伴随着煤的产生而存在。

尽管在技术在近几十年来的发展，瓦斯灾害尚未完全避免。

瓦斯气体随着开采深度的增加而增多，甲烷排放量高的地方，也适用于其他采矿有关的情况，如生产的增长率及其后果：难以控制的甲烷浓度增加，机械化程度提高，使用炸药和不重视气控制系统。

本文的主要目的是建立实地测量，使用一些不标准的采矿控制风险评估方法的一部分，并分析了深部煤层瓦斯矿井直立的行为，以及防止发生瓦斯事故的关键参数。

最终目标是在开采条件的改善，提高矿井的安全性。

为此，设置了两个不同的地雷仪表进行矿井控制和监测。

这两个煤矿属于Riosa-Olloniego煤田，在西班牙阿斯图里亚斯中央盆地。

仪器是通过subhorizontal能级开采的，一个约1000米的山Lusorio根据实际深度覆盖的地区。

在本研究中，一个是有利于瓦斯突出的易发煤（第八层），测定其气体压力及其变化，这将有助于提供以前的特征以完成数据，并评估第一次测量的网站潜在的爆发多发地区提供一些指导。

本文运用一个气体测量管设计了一套用于测量一段时间由于附近的运作的结果，计算低渗气压力以及其变化。

本文建立了作品的重叠效应，但它也表明了两个预防措施和适用功效，即高压注水和一个保护煤层（第七层）的开采，必须优先开采保护层以防止瓦斯气体的涌出。

这两项措施构成的开采顺序，提高矿井安全性。

因此，应该完成系统的测量控制风险：在8煤层瓦斯压力影响的其他地区，要建立最合适的时刻进行开采作业。

进一步的研究可以把重点放在确定的渗透，不仅在瓦斯爆炸危险区，而且在那些还没有受到采矿的工作和更精细的调整过载时间的影响范围和矿井第7
煤层和第8煤层之间的瓦斯气体。

关键词：煤矿，煤层气，气体压力渗透率瓦斯突出
1 简介
近年来，煤层气体和煤矿瓦斯研究蓬勃发展。

由于天然气的生成量将继续是某些国家的未来几年不断增长的行业。

例如，中国，其中790万立方米的甲烷涌出在1999年关闭（黄，2000），估在计发达国家矿区煤层气潜力为30铥（朱，2000）。

由泰勒等人的估计，（1992）在美国就地天然气约为19铥，而德国的煤层气资源总量估计有3铥，非常相似。

据波兰文或英文资源（世界煤炭研究所，1998年）这使电子商务增加对煤层气的研究开辟了新的生产线，也使科学界加强对煤炭的propertiesof一些知识和沼气方面有关属性决定的气体流量的，直到现在已还没有完全得到充分的分析。

其中一些参数是影响了煤炭开采危害的发生，瓦斯有可能导致致命的或危险性事故。

现代采矿死亡和受伤矿工名单已逐步增加，例如在1906年3月发生了一起超过1000名人员伤亡的煤矿事故。

但在西方国家的增长速度却在下降。

西班牙近年来最严重的矿难发生在8煤层气。

例如，1995年8月31日造成14名矿工死亡的圣尼古拉斯煤矿事故中，引起了关于煤矿安全的广泛研究。

在第8煤层气发生的Nicolásmine致命意外，导致不同的调查研究。

如“研究项目中的8煤层气在863区”，2003年之间的奥维多和Hunosa大学（“研究瓦斯突出的预防”，2003年，由安保部的Hunosa:“科研的圣尼古拉斯和Montsacro8煤层气“，2004年奥维多大学之间和区域工业，商业和旅游部阿斯图里亚斯）为了实现这更好的煤层气知识及其行为，改善安全生产条件和从而减少未来的风险。

弗洛雷斯（1998）提出，有一个与瓦斯突出（煤矿安全），并在地下矿井生产（排雷行动和地雷经济效率）的关系。

自8煤层气是经济，管理没有考虑到它结束在采矿作业的选项。

通过第八煤层的2个开采矿山：上述圣尼古拉斯在Ablaña（Mieres）和Montsacro，在Riosa。

此项研究已在这两个矿山的地方，有一个不容置疑的重要性在orderto履行一定的差距：以量化的煤层气第八煤层一些很相关的采矿危
害（如煤气压力）未知参数，提高了矿石的开采顺序，开采方法（非常相关的一个因素后，蒂勒曼等。

2001年，突然爆发的风险），建立了应用或划定危险区的防治对策一些准确性。

2 说明中央盆地和阿斯图里亚斯8煤层气
iosa- Olloniego单位的第八煤层，在阿斯图里亚斯中央煤盆地西南（在坎塔布连山脉，IGME，1985年最大的煤盆地）位于具有煤层气约4.81是GM3潜力。

这是大约19.8％的阿斯图里亚斯中部盆地的资源估计数和12.8％的总评估西班牙煤层气资源（萨帕特罗等，2004）。

3.84在第8煤层气煤层气的潜力是GM3属于圣尼古拉斯和Montsacro：1.08是GM3到圣尼古拉斯面积和2.76Gm3到Riosa，下至-800级（IGME，2002）。

煤层主要集中在威斯特伐利亚（苏亚雷斯- Ruiz和希门尼斯，2004年）大陆沉积物。

该Riosa- Olloniego地质单元的三缝系列组成：埃斯佩朗莎与总厚度350米，包含3-6为3.5至6.5米厚煤层煤炭累积; Pudingas，这是700米厚，具有3-5为5-7米厚煤层，而卡纳莱斯系列，最重要的一个与8-12煤层，我800米厚，该款项高达12-15米厚。

这个系列，其中包含8煤层气，在此学习兴趣煤层气，拥有10.26mat SanNicolás和15.13matMontsacro总厚度（Pendás等。

，2004）。

图。

1显示了两个煤矿地质图，而图。

2represents两者地雷正视图和仪表地区的位置。

在这个特殊的研究，第八届煤层气位于一间993和一○一七米，在低烈度区seismi深度。

本机的可开采煤层主要集中在威斯特伐利亚（苏亚雷斯- Ruiz和希门尼斯，2004年）大陆沉积物。

该Riosa- Olloniego地质单元的三缝系列组成：埃斯佩朗莎与总厚度350米，包含3-6为3.5至6.5米厚煤层煤炭累积; Pudingas，这是700米厚，具有3-5为5-7米厚煤层，而卡纳莱斯系列，最重要的一个与8-12煤层，我800米厚，该款项高达12-15米厚。

这个系列，其中包含8煤层气，在此学习兴趣煤层气，拥有10.26mat SanNicolás和15.13matMontsacro 总厚度（Pendás等。

，2004）。

图。

1显示了两个煤矿地质图，而图。

2represents 两者地雷正视图和仪表地区的位置。

在这个特殊的研究，第八届煤层气位于一间993和一○一七米，在低烈度区seismi深度。

M.B.迪亚斯阿瓜多尔冈萨雷斯Nicieza/煤炭地质69（2007）253-266国际杂志
图1 地质图。

以及在不同的研究中引用的部分
在盆地地质结构，对煤层应力状态及周边围岩和两个含煤地层的一些性质和煤层本身。

接下来的段落总结了本研究项目开始时的状态。

研究人员研究煤突出与地质因素的关系。

（曹等2001年）发现，在四个矿区进行了分析，改变周围的爆发在逆断层构造带发生，这将有助于突出划定易发区。

在8煤层气，在过去的一些轻微的爆发可能与故障或在煤层厚度变化。

因此，一般的地质进行了系统检查，以及任何可能出现的异常情况每日监测。

但是，在任何情况下，一些其他的爆发可能与当地也没有一般故障。

图2一般位置的研究领域。

M.B.迪亚斯阿瓜多尔冈萨雷斯Nicieza/煤炭地质69（2007）253-266国际杂志一些年来，负责技术专家在煤研矿究了压力状况下工作面端头或残留岩体预测理论计算，意味着潜在的危险地区，根据俄罗斯的标准（安全煤和油页岩的矿工，1973年规例）煤层气的。

假设有一个初步的办法来应力状态，这个参数，因此没有包括在这个文件中提出的研究性学习。

在中央阿斯图里亚斯煤盆地，无论是孔隙度和含煤地层渗透率非常低，夹板结构不发达和夹板通常是充满水，甚至矿化。

因此， 5.10立方米/吨在诸如澳大利亚（比米什和Crosdale，1998年）或德国，一个瓦斯突出危险性的价值已建立当甲烷浓度超过9立方米/吨（尽管接近超压区，此风险值下降到5.5立方米/吨）。

由于在煤层瓦斯含量平均与那些鲁尔盆地（而据科德宝集团等。

1996年，从0变化到15立方米/吨）相比，在第8煤层气的价值将接近的风险值。

威廉姆斯和韦斯曼（1995年），最重要的瓦斯压力梯度与前脸结合参数。

瓦斯解吸率（V1）的已被定义为甲烷量立方厘米表示，这是从10克煤样解吸与0.5和0.8毫米之间，晶粒尺寸，在一个35秒（fromsecond 35个时间段70测试）。

解吸率计算从2米，3米和7米的样本，经技术规范0307-2-92对西班牙工业部的诉讼。

在研究过程中，平均得到的值是：0.3立方厘米/（10克•35 s）在2米的深度，0.5立方厘米/（10克•35 s）在3米和一点六立方厘米/（10克•35 s）在甲烷流量只有路径开放性骨折。

煤矿瓦斯含量是先前已被划分的主要参数之一。

在盆地中部的甲烷浓度变化阿斯图里亚斯4至14立方米的煤/吨（苏亚雷斯费尔南德斯，1998年）。

特别是，在Riosa - Olloniego单位，气体含量为3.79到9.89立方米/吨的
煤（Pendás等，2004）。

在研究，在研究领域有各种不同的测量值之间的4.95和8.10立方米/吨，平均value7m.Maximumvalues，都是一点七立方厘米/（10克•35 s）在2米的深度，在3.3和高达3米到四点三立方厘米/（10克•35 s）在7 m.The 初始临界安全值，以避免在8煤层气瓦斯突出是二立方厘米/（10克•5秒）。

由于在这一事件的调查研究发现，限制值降低到一点五立方厘米/（10克· 35秒）。

但是其他的属性，如煤气压力，煤炭本身的结构和通透性，有beeninsufficiently特点是Riosa Olloniego单位在此之前研究性学习。

先前已经有两种方法用于确定在煤矿瓦斯压力：为应力状态分析和应用的鲁尔盆地（德国）制订的标准获得了煤层瓦斯压力的理论计算间接测量俄罗斯，波兰和前苏联。

这些间接测量或测试钻孔的Jahns罚款（布劳纳，1994年），其中规定，当一个潜在的危险，罚款超过限值。

虽然有表列的鲁尔盆地煤层值，它是不适合的Riosa - Olloniego单位煤的情况。

因此，在该文件中的气体压力测量技术的改进，提出了发展的方法和设备在现场直接测量压力的能力。

第八层气是易碎烟煤，高镜质组含量，局部改造成面理化面料其中，当受到进入工作面支承压力（阿尔珀恩，1970），甲烷块迁移。

用低挥发分，它的形成过程中的后期阶段和煤化，正如由弗洛雷斯（1998年），这相当于一个大的甲烷产生量。

此外，煤炭是受突如其来的厚度变化（开采条件，在不可预知的结果）和床平行剪切内的煤层气，已审议了关于瓦斯突出（李，2001）的影响。

其透气性从来没有被量化，然后在该矿区。

因此，在煤层气研究中的第八，决定进行原位测试，以测量压力瞬变，获得网站的价值观，让未来的网站渗透率的计算，以验证是否小于5毫，限制值，达赖喇嘛和Bodziony后（1998年），使一对突出煤层负责。

因此，在本研究中，我们试图描述气体的压力和压力瞬变，为它们在发生瓦斯突出或事件的重要性，其中一个突出暴力的发生是由于煤的能量突然释放，由大量的气体释放的陪同下（冈萨雷斯Nicieza等，2001年），无论是在突破或在煤层（Hardgraves，1983年）的发展。

3 结论
煤层气的主要危险是影响安全的一些煤矿井下andproductivity。

本文强调了
8煤层气倾向引起瓦斯突出，由于履行的风险因素，已量化为煤层气的第8和第一次是非常相关的采矿危害系列：气体的压力和变化，高valuesmeasured在煤层气，获得较低的寄存器在Montsacro比圣尼古拉斯（其中480千帕的压力测量中的气体达到最大深度）。

这些参数，随着浓度和解吸率测量系统的那些已经正在开展的排雷工作人员一起出去，需要监测和控制。

一个气体测量管设计了一套，用于测量气体压力及其变化，以及附近的运作的影响，以确定outburstprone 地区，作为一种预防性措施注射液表明了这些测量管的手段。

注射液在降低煤层气压力，虽然测试的所有必须进行最大化的预防措施，因为瓦斯突出过程中可能会出现本身。

结果表明该仪器convenienceof煤层气开采的第七至少一个分段提前8煤层气。

这意味着已完成综采放顶煤综都相应向东和向西，并具有必要的时间来让流逝的扩张生效。

这扩张的时间估计两至三个月。

所构造的仪器也允许重叠的运作效果来衡量：由于煤层综采放顶煤的坐落于煤层的方法检测的屋顶的第八届煤层气，一个在气体压力的增加是推动区域生产在8煤层气。

这甚至可能一式三份的气体压力，更为突出的综采放顶煤方法的测量设备的位置。

作者对一些55-60米空间范围综放开采的影响，估计和2-3个月的时间期限。

本文的主要贡献在居住的控制和瓦斯突出矿井中，以补充自身的系统性风险的措施theproposal测量，以提高矿山安全生产的目的。

这除了某些实际改进工作首先在矿业开发方面的顺序，建议，将涉及提前启动之前或在运作重叠的气体测量管安装。

这将包括intemporarily扣留提前在8煤层气的运作时，可能会出现重叠或之前，一个在8煤层气提前开始，安装在脸上测量管。

价值观和对测量气体压力的趋势与来自气体浓度测试得到的数据，将使对煤层气的条件控制和什么时候可适当延长提前建立。

气体测量管道将因此成为一个可靠，经济控制和风险评估的瓦斯突出的措施。

此外，这种设备将启用，既为校准时间和矿业在每个工作的影响范围内预先研究openingof其他线路，以及为计算煤的渗透性。

通过对设计的测试（气两gasmeasurement管集流）的方法，可估计渗透率通过与网站的数据校正数值模
型，无论是在矿山领域仍然被挖掘工作，并在那些已经受到影响采矿工程。

这些校准也将允许具有的深度在煤层透气性变化本身进行分析。

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原文:
Control and prevention of gas outbursts in coal mines,
Riosa–Olloniego coalfield, Spain
María B. Díaz Aguado C. González Nicieza Abstract Underground coal mines have always had to control the presence of different gases in the mining environment. Among these gases, methane is the most important one, since it is inherent to coal. Despite of the technical developments in recent decades, methane hazards have not yet been fully avoided. This is partly due to the increasing depths of modern mines, where methane emissions are higher, and also to other mining-related circumstances, such as the increase in production rates and its consequences: difficulties in controlling the increasing methane levels, increasing mechanization, the use of explosives and not paying close attention to methane control systems.
The main purposes of this paper are to establish site measurements using some critical parameters that are not part of the standard mining-control methods for risk assessment and to analyze the gas behavior of subvertical coal seams in deep mines in order to prevent gas incidents from occurring. The ultimate goal is the improvement in mining conditions and therefore in safety conditions.
For this purpose, two different mines were instrumented for mine control and monitoring. Both mines belong to the Riosa–Olloniego coalfield, in the Asturias Central Basin, Spain and the areas instrumented are mined via subhorizontal sublevels at an actual depth of around 1000 m under the overburden of Mount Lusorio.
During this research, a property favoring gas outbursts was site measured for the first time in an outburst-prone coal (8th Coalbed), gas pressure and its variations, which contributed to complete the data available from previous characterizations and to set some guidelines for assessing the potential outburst-prone areas. A gas-measurement-tube set has been designed for measuring gas pressure as well as its variation over time as a result of nearby workings and to calculate permeability.
The paper establishes the effect of overlapping of works, but it also shows the efficacy of two preventive measures to be applied: high pressure water infusion and the exploitation of a protective coal seam (7th Coalbed), that must be mined preferably two complete sublevels before commencing the advance in the outburst-prone coalbed. Both measures constitute an improvement in the mining sequence and therefore in safety, and should be completed with a systematic measurement to control the risk: gas pressure in the 8th Coalbed in the area of
influence of other workings, to establish the most suitable moment to renew the advance. Further researches could focus on ascertaining the permeability, not only in mined areas but also in areas of the mine that are still not affected by mining work and on tuning more finely the ranges of influence of overstress time and overlap distance of the workings of the 7th Coalbed in the 8th Coalbed.
1. Introduction
Coalbed and coal mine methane research is thriving due to the fact that power generation from coal mine methane will continue to be a growing industry over the coming years in certain countries. For instance, China, where 790 Mm3 of CH4 were drained off in 1999 (Huang, 2000), has 30 Tm3 of
estimated CBM potential in the developed mining areas (Zhu, 2000). The estimate by Tyler et al. (1992) of the in-place gas in the United States is about 19 Tm3, while Germany's total estimated coalbed methane resources are 3 Tm3, very similar to Polish or English resources (World Coal Institute, 1998).
This increase in the CBM commerce has opened up new lines of research and has allowed the scientific community to increase its knowledge of some of the propertiesof coal and of methane gas, above all with respect to the properties that determine gas flow, which until now had not been sufficiently analyzed. Some of these parameters are the same ones that affect the occurrence of coal mining hazards, as methane has the potential to become a source of different fatal or non-fatal disastrous events.
Since the famous mining catastrophe with over 1000 fatalities in Courrières, France, in March 1906, the list of dead and injured miners in modern mining has grown progressively, but growth in Western countries is at a decreasing rate. Fourteen miners died in the 8th Coalbed at San Nicolás mine on 31 August 1995, the worst mining accident in recent years in Spain. Major concern was aroused in the region with respect to mining-related safety problems.
The fatal accident in the 8th Coalbed at San Nicolásmine has led to different research st udies (such as the“Research project of the 8th Coalbed in the 863 area”, 2003, between the University of Oviedo and Hunosa;“Research of Prevention of Gas Outbursts”, 2003, by the Department of Safety of Hunosa; “Research of the 8th Coalbed in San Nicolás a nd Montsacro”, 2004, between the University of Oviedo and the Regional Industry, Commerce and Tourism Ministry of Asturias) for achieving a better knowledge of this coalbed and its behavior in order to improve safety conditions and thus to minimize future risks. As Flores (1998) suggested, there is a relationship between gas outbursts (mine safety) and production in underground mines (efficiency of mine operations and mine economics). Since the 8th Coalbed is economical, the management has not considered the option of ending mining operations in it.
The 8th Coalbed is mined via two mines: the aforementioned San Nicolás, in
Ablaña (Mieres) and Montsacro, in Riosa. This research study has taken place in both mines and has an unquestionable importance in orderto fulfill some gaps: to quantify some unknown parameters of the 8th Coalbed very related to mining hazards(such as gas pressure), to improve the mining sequence in the sublevel method (a factor very related, after Thielemann et al, 2001, with the risk of sudden outbursts), to establish the accuracy of some of the prevention measurements applied or to delimit the hazardous areas.
2. Description of the Asturian Central basin and of the 8th Coalbed
The 8th Coalbed of the Riosa–Olloniego unit, located in the Southwest of the Asturian Central Coal Basin (the largest coal basin in the Cantabrian Mountains, IGME, 1985), has CBM potential of about 4.81 Gm3. This is around 19.8% of the estimated resources of the Asturian Central Basin and 12.8 % of the total assessed CBM resources in Spain (Zapatero et al, 2004). 3.84 Gm3 of the CBM potential of the 8th Coalbed belongs to San Nicolás and Montsacro: 1.08 Gm3 to San Nicolás area and 2.76Gm3 to Riosa, down to the −800m level (IGME, 2002).
The minable coalbeds of this unit are concentrated in Westphalian continental sediments (Suárez-Ruiz and Jiménez, 2004). The Riosa–Olloniego geological unit consists of three seams series: Esperanza, with a total thickness of 350 m, contains 3–6 coalbeds with a cumulative coal thickness of 3.5 to 6.5 m; Pudingas, which is 700 m thick, has 3–5 coalbeds with a thickness of 5–7m; whereas the Canales series, the most important one, I 800 m thick, with 8–12 coalbeds that sum up to 12–15 m thick. This series, which contains the 8th Coalbed, the coalbed of interest in this study, has a total thickness of 10.26mat SanNicolás and 15.13matMontsacro (Pendás et al, 2004). Fig. 1 shows the geological map of the two coal mines, whereas Fig. 2represents a front view of both mines and the location of the instrumented areas. In this particular study, the 8th Coalbed is situated at a depth of between 993 and 1017 m, in an area of low seismi intensity.
Instantaneous outbursts pose a hazard to safe, productive extraction of coal in both mines. The mechanisms of gas outbursts are still unresolved but include the effect of stress, gas content and properties of the coal. Other factors such as geological features, mining methods, bord and pillar workings or increase in rate of advance may combine to exacerbate the problem (Beamish and Crosdale, 1998). Some of the main properties of the 8th Coalbed favoring gas outbursts (Creedy and Garner, 2001; Díaz Aguado, 2004) had been previously studied by the mining company, in their internal reports M.B. Díaz Aguado, C. González Nicieza / International Journal of Coal Geology 69 (2007) 253–266 255
Fig 1 Geological map.
as well as in the different research studies cited in Section
The geological structure of the basin, the stress state of the coalbed and its surrounding wall rock and some properties of both coal-bearing strata and the coalbed itself. The next paragraphs summarize the state of the research when this project started.
Many researchers have studied relationships between coal outbursts and geological factors. Cao et al (2001), found that, in the four mining districts analyzed, outbursts occurred within tectonically altered zones surrounding reverse faults; this could help to delimit outburst-prone zones. In the 8th Coalbed, some minor outbursts in the past could be related to faults or changes in coal seam thickness. Hence, general geological inspections are carried out systematically, as well as daily monitoring of any possible anomalies. But, in any case, some other outbursts could be related neither
to local nor general faults.
Fig 2 General location of the study area.
M.B. Díaz Aguado, C. González Nicieza / International Journal of Coal Geology 69 (2007) 253–266
For some years now, the technical experts in charge of the mine have been studying the stress state of the coalbed by means of theoretical calculations of face end or residual rock mass projections that indicated potential risk areas, based on Russian standards (Safety Regulations for Coal and Oil Shale Miners, 1973).Assuming that there was an initial approach to the stress state, this parameter was therefore not included in the research study presented in this paper. In the Central Asturian Coal Basin, both the porosity and permeability of the coal-bearing strata are very low,the cleat structure is poorly developed and cleats are usually water-filled or even mineralized. Consequently, of 5.10 m3/t. In some countries, such as Australia (Beamish and Crosdale, 1998) or Germany, a gas outburst risk value has been established when methane concentration exceeds 9 m3/t (although close to areas of over-pressure, this risk value descends to 5.5 m3/t). As the average gas contents in the coalbed are comparable with those of the Ruhr Basin (which according to Freudenberg et al, 1996, vary from 0 to 15 m3/t), the values in the 8th Coalbed would be close to the risk values.
Desorption rate was considered the most important parameter by Williams and Weissmann (1995), in conjunction with the gas pressure gradient ahead of the face. Gas desorption rate (V1) has been defined as the volume of methane, expressed in cm3, that is desorbed from a 10 g coal sample, with a grain size between 0.5 and 0.8 mm, during a period of time of 35 s (fromsecond 35 to 70 of the test). Desorption rates have been calculated from samples taken at 2 m, 3 m and 7 m, following the proceedings of the Technical Specification 0307-2-92 of the Spanish Ministry of Industry. The average values obtained during the research are: 0.3 cm3 / (10 g·35 s) at 2 m depth, 0.5 cm3 / (10 g·35 s) at 3 m and 1.6 cm3 / (10 g·35 s) at the only paths for methane flow are open fractures. Coal gas content is one of the main parameters that had been previously analyzed. The methane concentration in the Central Asturian Basin varies between 4 and 14 m3/t of coal (Suárez Fernández, 1998). Particularly, in
the Riosa–Olloniego unit, the gas content varies from 3.79 to 9.89 m3/t of coal (Pendás et al, 2004). During the research, the measured values in the area of study have varied between 4.95 and 8.10 m3/t, with an average value7m.Maximumvalues were of 1.7 cm3 / (10 g·35 s) at 2m depth, 3.3 at 3 m and up to 4.3 cm3 / (10 g·35 s) at 7 m.The initial critical safety value to avoid gas outbursts in the 8th Coalbed was 2 cm3 / (10 g·35 s). Due to incidents detected during this research study, the limit value was reduced to 1.5 cm3 / (10 g·35 s).
But other properties, such as coal gas pressure, the structure of the coal itself and permeability, had beeninsufficiently characterized in the Riosa Olloniego unit before this research study.
Two methods had been previously employed to determine the gas pressure in the mine: the Russian theoretical calculations for the analysis of the stress state and the indirect measurements of the gas pressure obtained by applying criteria developed for the coalbeds of the Ruhr Basin (Germany), Poland and the former Soviet Union. These indirect measurements were the Jahns or borehole fines test (Braüner, 1994), which establishes a potential hazard when the fines exceed a limiting value. Although there are tabulated values for the coalbeds of the Ruhr Basin, it is not the case for the coals of the Riosa–Olloniego unit. Therefore, in this paper an improvement to the gas pressure measurement technique is proposed by developing a method and a device capable of directly measuring in situ pressures.
The 8th Coalbed is a friable bituminous coal, high in vitrinite content, locally transformed into foliated fabrics which, when subjected to abutment pressure, block methane migration into working faces (Alpern, 1970). With low-volatile content, it was formed during the later stages of coalification and, as stated by Flores (1998) this corresponds to a large amount of methane generated. Moreover, the coal is subject to sudden variations in thickness (that result in unpredictable mining conditions) and to bed-parallel shearing within the coalbed, that has been considered an influence on gas outbursts (Li, 2001). Its permeability had never been quantified before in this mining area. Thus, during research in the 8th Coalbed it was decided to perform in situ tests to measure pressure transients, to obtain site values that will allow future calculations of site permeability, in order to verify if it is less than 5 mD, limit value which, after Lama and Bodziony (1998), makes a coalbed liable to outbursts.
Therefore, in this study we attempted to characterize gas pressure and pressure transients, for their importance in the occurrence of gas outbursts or events in which a violent coal outburst occurs due to the sudden release of energy, accompanied by the release of significant amount of gas (González Nicieza et al,2001), either in breaking or in development of the coalbed (Hardgraves, 1983).
3. Conclusions
Coalbed is still a major hazard affecting safety andproductivity in some underground coal mines. This paper highlights the propensity of the 8th Coalbed to
give rise to gas outbursts, due to fulfilling a series of risk factors, that have been quantified for 8th Coalbed for the first time and that are very related to mining hazards: gas pressure and its variation, with high valuesmeasured in the coalbed, obtaining lower registers at Montsacro than at San Nicolás (where 480 kPa were reached in the gas pressure measurements at the greatest depth). These parameters, together with the systematic measurement of concentration and desorption rate that were already being carried out by the mine staff, require monitoring and control. A gas-measurement-tube set was designed, for measuring gas pressure and its variations as well as the influence of nearby workings to determine outburstprone areas. The efficacy of injection as a preventative measure was shown by means of these measurement tubes. Injection decreases the gas pressure in the coalbed, although the test must be conducted maximizing all the precautionary measures, because gas outbursts may occur during the process itself.
The instrumentation results indicated the convenienceof mining the 7th Coalbed at least one sublevel ahead of the 8th Coalbed. This means having completed longwall caving of the corresponding sublevel both eastward and westward, and having allowed the necessary time to elapse for distention to take effect. This distention time was estimated between two and three months.
The constructed instrumentation likewise allowed the effect of overlapping of workings to be measured: as the longwall caving of the coalbed situated to the roof of the instrumented coalbed approaches the area of advance of the 8th Coalbed, an increase in the pressure of the gas is produced in the 8th Coalbed. This may even triplicate the pressure of the gas and is more pronounced as the longwall caving approaches the position of the measuring equipment. A spatial range of the influence of longwall caving of some 55–60 m was estimated and a time duration of 2–3 months.
The main contribution of this article resides in theproposal of measures of control and risk of gas outbursts that complement the systematic measurements in the mine itself, with the aim of improving safety in mining work. This proposal, apart from certain practical improvements in mining work, above all regarding the exploitation sequence, would involve the installation of gas measurement tubes before initiating the advance or at the overlap of workings. It would consist intemporarily detaining the advance in the 8th Coalbed when an overlap of workings may occur or prior to the commencement of an advance in the 8th Coalbed, installing measurement tubes in the face. The values and the trend of the measured gas pressures, together with the values obtained from gas concentration tests, would enable control of the conditions of the coalbed and the establishing of what moment would be appropriate to renew the advance. The gas measurement tubes would hence be a reliable, economic control and evaluation measure of the risk of gas outbursts.
Furthermore, this equipment would enable the openingof other lines of research, both for calibrating the time and range of influence of mining work in each advance, as well as for calculating the permeability of the coal. By means of the designed test。