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原文：Introduction of firefighting methods in U S underground minesIntroduction Underground mine fire always exists since the mining activity was practiced It poses a severe safety hazard to the mine workers and may also cause a tremendous economic loss to the mines Methods for controlling and extinguishing fires in underground mine have long been studied and there have been significant improvements In order to know clearly about the firefighting technology used this paper summarizes most of the underground mine firefighting methods used in the United States the past 150 years This paper describes not only the accepted firefighting theories but also the technologies both direct and indirect attacking in accordance to regulations or codes with special attention is given to the indirect attack method and its related technologies Further research needed is also briefly discussed at the end of this paper Underground coal mine fires in the United States continue to present a significant hazard to the safety and health of mine workers Unlike other types of mining accidents where an incident generally involves only a few workers the danger of a mine fire extends to every person working Comparing with other industries underground mine fires more hazardous Since the underground coal mines are confined in space toxic fumes from the fires will gather in the openings and it is impossible for these toxic fumes to be quickly diffused through intake or return airways resulting in increased toxic gas concentrations in underground airways 1 When a mine fire occurs the toxic products of combustion can block avenues of escape and these asphyxiating gases can spread well beyond the fire zone in a short period of time There have been significant improvements in mine safety and health since the passing of the Federal Coal Mine Health and Safety Act of 1969 generally referred to as the Coal Act In 1973 Mine Enforcement and Safety Administration MESA was created to assume the safety and health enforcement function formerly carried out by the Bureau of Mines This was changed in 1977 through the Federal Mine Safety and Health Act of 1977 Mine Act which amended the Coal Act in a number of significant ways including the establishment of the Mine Safety and Health Administration MSHA which performs all enforcement functions1Basic Theories Underground mine fire is the combustion process under mine ventilation conditions Happened in underground airways and involved by the ventilation system made it mostly different from other kind of fires Therefore to understand how fire can be fought effectively it is necessary to know a little knowledge about combustion and ventilation 1 1 Fire Triangle and Tetrahedron For many years the concept of fire was symbolized by the fire triangle It consists of fuel heat and oxygen Further fire research determined that a fourth element a chemical chain reaction was a necessary component of fire So the fire triangle has largely been replaced in the industry by the fire tetrahedron to reflect this fourth element which provides a more complete understanding In these four elements the oxygen sustains the combustion sufficient heat raises the material to its ignition temperature the fuel provides the combustible material and subsequently an exothermic chemical chain reaction exists in the material Theoretically removal of any one of these essential elements will result in the fire being extinguished 1 2 Leakage Control Theory Usually at fires incipient stage to remove the heat and the ignition material out of the fire zone is possible since access to the fire zone may still be safe However when the fire is developed and out of control the effort of firefighting is mainly focus on other aspects such as removing the oxygen out of the triangle and interrupting the chemical chain reaction in the tetrahedral This approach was commonly practiced by injecting inert gases into the sealed area to dilute the oxygen concentration in and around the fire zone However experience showed that it is impossible to seal the fire section entirely The fresh air can always enter the sealed section from the surface stoppings or other unsealed area through broken strata and the combustion products can leave the sealed fire zone Field experience shows that if the fire zone is not effectively sealed inertization can never be effective where fire will most likely be out of control Two ways have been used to lower leakage decrease the pressure differential between the sealed and unsealed area and increase the airway resistant value along the opening These two methods have been commonly practice in firefighting. 2Firefighting Technologies2 1Direct Attack Direct attack is the most effective and commonly used method in controlling and extinguishing a mine fire When fire occurs the most important thing is to fight fire with materials or tools at hand immediately Usually water rock-dust and portable extinguishers are the most convenient means to fight fire as soon as the fire was discovered at incipient stage 7 2 1 1 Traditional Direct Attack Methods Water is the first agent coming into mind when fire happened Water sprays and water hoses may be used to quench the fire with success when the fire is limited in scale But since dense volumes of steam are given off when water is placed on the fire use of water demands a certain amount of care Coatesworth 1929 Using rock-dust to control mine fire at the beginning stage has also been practiced ever since the beginning of mining Howarth and McCaa 1929 The chief advantage of this method is that there is no hot steam produced But when the fire is in the roof or on vertical surfaces it will be a difficult matter to cover such a fire entirely with a heavy layer of rock-dust Digging out the combustion materials has been used to deal with gob fires since 1915 Morris 1987 and it should be clear that this method should be used only when fire is confined to only a small area 2 1 2 Improved Direct Attack Methods All the methods described above can be effective only if the fire is still in its incipient stage and the fire zone is safely accessible When firefighting activities are delayed the fire is developed and impossible for mine workers to approach the fire zone close enough due to intensive heat smoke or hazardous roof conditions The approach to the seat of the fire from the intake is often limited by the backing of smoke and hot gases against the ventilation current Fig2 by the heat from the strata and lastly by falls of roof Eisner and Shepherd 1953 /54 Mitchell1962 Since the smoke backed upstream some distance against an intake air-flow an increase in the airflow velocity can reduce the length of the smoke tongue So placing a fire-resistant brattice acting as a good radiation screen across the lower half of the roadway was practiced as an effective way to fight back the tongue of smoke Fig 3 This method was used at White-haven in 1910 Morris 1987 In this case the mine workers can advance Backing Movement of Smoke 2 FigEisner and Shepherd 1953 /54 from downstream some distance to the fire The effective distance for extinguishing the fire is governed by the cross sectional area of the roadway and the pressure of the extinguishing fluid at the pipe These methods which applied the extinguishing agents and devices directly to the fire are able to fight a fire at its early stage It also places miners in close proximity to the fire and exposes them to the deadly hazards of the fire Moreover if the underground access is blocked from outside personnel the fire zone is too large for available underground personnel or the supply of available firefighting materials and devices are limited it is impossible to access to the fire zone to fight fire directly indirect firefighting method is needed2 2Indirect Attack The indirect attack method is used to control the underground mine fires beyond their incipient stage Although most mine fires were extinguished in their early stages there were still some uncontrolled fires that require indirect firefighting method when direct method is not possible Basically the indirect attack method was mainly based on sealing off the affected area so the fire will distinguish by oxygen depletion When the affected fire zone was sealed water foam inert gases or other inert materials are injected into the fire zone to expedite the process Depending on specific conditions sealing operation can be either carried out underground through remote sealing technology or from surface Other indirect attack methods such as pressure balancing ventilation reversal are also used in practice 8 2 2 1Sealing within Mine The principle of sealing off an underground section is to construct temporary or permanent partitions to keep the air from entering the fire zone After the affected area was sealed high expansion foam or inert gases /materials need to be injected through the seal into the fire area Building permanent partitions can be a labor-intensive time-consuming and dangerous process So in order to seal off a fire area as quickly as possible temporary seals are often constructed before permanent seals Fig 4 They must be airtight by using brattice cloth concrete blocks or wood and sometimes sprayed with special material for reinforcement In 1991the former Bureau of Mines has investigated the use of a parachute stopping as a quick-erect check curtain during mine fires and the concept has been tested in several mines Fig 5 The Regulator Parachute Stopping is used as temporary air stopping or controlling airflow insulated ducting for hot mines and reducing leakage to virtually zero Kissell and Timko1991 In every instance when a parachute stopping was erected on the section the intakeFig 4Traditional temporary pressure went up substantially which helps to keep smoke out of the intake es-partition Conti1995cape way Experiments indicate that this method may serve as a viable way to earn the time for building the permanent stoppings The inflatable feed-tube partition which are inflated with compressed-air underground or deployed through a borehole from the surface have also been experimented with by the former Bureau of Mines in 1995Fig 6 It is a lightweight portable rectangular inflatable bag that can be used by firefighters to rapidly seal off large openings such as those in underground mines and to simultaneously provide a feed tube for a high-expansion foam generator Conti1995 Unfortunately the two technologies are still at an experimentalFig 5Sketch of parachute placed on the stage no actual application has been reported Although the idea is intake section Kissell and Timko1991 creative there are a lot of problems in practice The main reason is that a seal must not only be capable of preventing an explosion from propagating into or out of the sealed area but also be able to hold the water foam or inert gases used to extinguish the fire Building seals using traditional methods are still been universally practiced 2 2 2 Sealing through Remote Technology When underground access is impossible or too dangerous to do so mine seal construction can be attempted through vertical boreholes Remote sealing involves the injection of fly-ash slurry concrete rigid foam or other inerted mixtures into mine airways from the surface to attempt to isolate the fire area In theory this remote method has great merit because boreholes can be drilled to reach specific areas of the mine and seals can be positioned close to a fire zone In this manner oxygen inflow can be controlled and the spread of a fire can be limited without exposing miners to the hazards However the process while appears to be good in theory is belabored by multiple problems in practice译文：美国煤矿防灭火方法的介绍前言采矿业盛行以来，矿井火灾始终存在。它不仅严重威胁了煤矿工人的安全,还可能造成巨大的经济损失。长期以来，各煤矿一直研究控制和扑灭火灾的方法，并且已经有了重大的改进。为了清楚地了解本文所使用的灭火技术，笔者总结了美国过去150年来大多数矿井的灭火方法。本文不仅描述了接受消防理论,而且根据规定或特别关注这些消除火灾技术，更是直接和间接地攻研了代码间接攻击方法及其相关技术。进一步研究了消防方法。 在美国，煤矿矿井火灾一直严重威胁着煤矿工人的安全和健康。与一般只涉及少数工人的安危的其他类型的矿难事件相比，煤矿矿井火灾延伸到每个人的工作，比其他行业火灾更危险。井下相伴而生的有毒气体会随矿井火灾自地下涌出并在井口聚集,而且这些有毒气体不可能很快扩散会通过吸附或逆转导致井底有毒气体浓度增加。矿井火灾发生时，燃烧的有毒气体会溢满逃生通道，并且在短时间内，这些窒息气体扩散距离远远超出了防火区。 自1969年联邦煤矿健康和安全法案通过，即通常所说的煤炭法案，矿山安全与健康就有了显著改善。在1973年，美国劳工统计局创建Mine Enforcement and Safety Administration （MESA）承担安全卫生执法功能。在1977年，联邦通过了矿山安全与健康法案，该法案修改了煤矿安全的许多重要方面,并且建立矿山安全与健康管理局去具体落实这些修改。1 基本理论矿井火灾是发生在矿井通风条件下的燃烧过程，它所涉及的井下主要管道和通风系统是不同于其他类型的火灾。因此，掌握燃烧和通风的相关知识，能够更好地做到矿井火灾的消防工作。1.1 三角形和四面体多年以来，人们通用三角形来表示燃烧的概念,它由燃料、热量和氧气。对火灾的进一步研究决定,第四个元素的化学连锁反应是燃烧的一个必要组成部分。所以火三角在很大程度上被火四面体取代，并且业内人士对这第四个元素提供了一个更完整的理解。在这四个元素中，氧气燃烧维持足够的热量增加了材料点火温度，再提供易燃材料,随后一个放热化学连锁反应理论上存在于材料，形成燃烧。而且删除任何一个要素都将导致火灾熄灭。1.2 泄露控制理论通常在火灾初期，从移除防火区的热量和点火材料，是可能实现安全访问防火区的。然而,大多控制和改善火灾消防的工作主要集中在其他方面,如消除三角形的氧气和打断四面体的化学连锁反应。给密封防火区域注入惰性气体降低其内部及周围的氧气浓度，这种方法得到普遍采用。然而经验表明,注入惰性气体是不可能完全密封火灾。新鲜的空气总是可以从表面进入密封部分或其他未封口的区域，并且可以通过破碎地层和燃烧的产物离开密封防火区。该领域的经验表明,如果防火区没有有效地密封，注入惰性气体将永远无法有效，而且火灾很可能失控。所以，与此同时，沿程提高抗气道值，被用于减少和降低密封泄漏区域和启封区域之间的压差。在矿井火灾的防灭技术中，这两种方法被普遍采用。2 防灭火技术2.1直接防灭火技术 在控制和扑灭矿井火灾中，直接防灭火技术是最有效和常用的方法。火灾发生时最重要的事情就是用材料或工具立即扑灭火灾。火灾在初期阶段，通常水、岩粉撒布器和便携式灭火器是最方便的抗火手段。2.1.1 传统的直接防灭火方法在发生火灾时，水是第一灭火剂。当火灾规模是有限的时，使用水喷雾和水软管灭火效果极好。但由于用水灭火时会产生大量的水蒸气，所以用水灭火的水量要慎重选择。1929年，Coatesworth使用岩粉控制矿井火灾的发生,从1929年矿业豪沃思和McCaa开始都还是处在开始练习阶段。该方法的主要优点是没有热蒸汽产生。但是,当火是在屋顶或垂直的表面,给火完全覆盖这样一个这的岩粉层将是一个很困难的问题。自1915年以来莫里斯1987，就清楚表明，挖掘燃烧材料已被用于处理采空区火灾，而且只有当火局限于小范围之内才使用这种方法。2.1.2改进的直接防灭火方法只有在火仍处于初期阶段，所有上述方法才是有效的,防火区才可以安全地访问。当火势继续发展足够接近顶板，而且煤矿工人无法接近防火区时，由于密集的热烟或危险条件，灭火工作就必然被推迟。 Eisner and Shepherd 1953 /54Mitchell1962提出，上述方法通过通风层的热量和最后冒落的顶板而进入火区，通常受烟雾和热气体的阻碍，是无法实现的。因为烟流