采空区漏风状况模拟及其分析.pdf

1994-2010 China Academic Journal Electronic Publishing House. All rights reserved. 采空区漏风状况模拟及其分析 陈明河 煤炭科学研究总院重庆研究院,重庆400037 摘 要通过建立综放采空区三维自然发火预测模型,采用数值模拟软件对高瓦斯煤层抽放条件下 综放采空区漏风状况进行了数值模拟,利用模拟结果对采空区进行了煤自燃“三带”的划分,并分析了 该工作面采空区浮煤自燃的危险区域及危险程度,可用来指导具有类似情况的采空区浮煤自燃火灾的 防治工作。 关键词瓦斯抽放;数值模拟;采空区;煤自燃;“三带” 划分 中图分类号TD75 2. 2 文献标识码A 文章编号1008 - 4495200901 - 0010 - 04 收稿日期2008 - 01 - 28;2008 - 11 - 03修订 基金项目“十一五” 国家科技支撑计划课题2006BAK 03B02 作者简介陈明河1974 , 男,福建长汀人,硕士,主要 从事煤矿防灭火安全技术研究。E - mail chenminghe78 163. com,电话023 - 65239355。 煤自燃火灾是我国煤矿主要灾害之一,严重威 胁煤矿安全生产。高瓦斯矿井的自燃火灾更难防 治,因其涉及瓦斯的治理。要治理好高瓦斯矿井工 作面采空区的煤自燃灾害,就要对采空区的漏风风 流情况、 瓦斯及氧气浓度分布情况有比较客观的了 解,才能更科学地制订综放面采空区防灭火技术措 施;避免因采用不科学的方法划分的采空区煤自燃 “三带” 而给防灭火工作带来不必要的麻烦和损失。 1 工作面概况及计算区域网格划分 1. 1 工作面概况 某矿4 - 2 煤层为高瓦斯煤层,平均厚度为 9197 m ,该煤层内布置了215工作面,上方213工作 面已开采。215工作面采用走向长壁后退式采煤方 法,利用机组和放顶煤落煤,采用液压支架支护,全 部垮落法控制顶板。215工作面倾向长约150 m ,与 213工作面之间的煤柱间距有25～30 m ,受采动的影 响,煤柱受压处于破裂状态,形成大量松散煤体。 215工作面机械采高一般为2. 65～3. 00 m ,放顶煤高 度一般在3～4 m ,因此215工作面采空区遗煤较厚, 平均达3. 00 m左右,如果考虑到煤体破碎后体积膨 胀此处按0. 3考虑 , 则该煤层采空区浮煤厚度平 均达到3. 90 m。根据该矿煤样自然发火实验,浮煤 厚度远远超过煤自燃的极限浮煤厚度,给工作面采 空区的煤自燃创造了极为有利的条件。215工作面 布置了2个抽放口,1号抽放口在回风侧处,出口在 走向方向上距离回风口80 m ,距离煤层底板垂直高 度10 m;2号抽放口在工作面顶板处,其出口在工作 面倾斜方向上距离回风口水平距离为30 m ,距离煤 层底板垂直距离为40 m。抽放口的具体位置及工作 面计算物理区域如图1所示。 图1 数值模拟区域模型 1. 2 计算区域网格划分 漏风区域主要分布在采空区开采煤层底板及其 以上40 m考虑到采空区的垮落 “三带” 及2号抽气 口的位置 , 宽度为工作面倾斜方向宽150 m ,计算 深度按深入到采空区内150 m ,为一六面体。根据工 作面结构特点,采用六面体计算元体,根据计算区域 上渗流速度 [1]在各个方向的变化 ,参考文献[2]确定 在垂直煤层Z方向,网络步长分别为0. 25 ,0. 5 , 1 m;工作面倾斜方向X和垂直工作面即工作面走 向方向Y网格步长为1 m。 2 模拟结果分析 采用数值方法研究瓦斯抽放时采煤工作面的采 空区自燃 “三带” 的分布规律,为防治采空区煤自燃 提供依据。对前述模型开展数值实验,可以得到采 空区不同位置的静压力、 瓦斯浓度、 氧气浓度和漏风 强度的分布规律 [3] 。渗流方向与压力等直线垂直, 01 2009年2月 矿业安全与环保 第36卷第1期 1994-2010 China Academic Journal Electronic Publishing House. All rights reserved. 因而可以得到抽放条件下采空区渗流方向 [1 - 4] 。模 拟结果如图23所示,分别为采空区距离煤层底板 2 m的水平剖面图和距离工作面60 m处的垂直剖面 图。图中X为工作面回风巷指向进风巷的方向,与 工作面平行;Y为自工作面回风指向采空区方向;Z 为垂直煤层向上方向。 图2 水平剖面压力分布 图3 垂直剖面压力分布 2. 1 采空区压力分布规律 从图23可以看出,采空区漏风自工作面进风 侧流入,从距离工作面回风侧30 m处的瓦斯抽放 口、 灌浆巷瓦斯抽放口和回风巷出口流出。靠近回 风侧压力低,而进风侧压力相对较高。 2. 2 采空区瓦斯浓度分布规律 抽放条件下采空区水平剖面瓦斯浓度分布规律 见图4 ,可以看出,实施抽放后,在采空区较深处,靠 近进风侧瓦斯浓度反而比回风侧高,这是由于在回 风侧和靠近回风巷的采空区上方布置了抽放口,对 瓦斯进行了抽放所致。在对瓦斯实施抽放后,工作 面的上隅角和靠近回风巷侧的采空区,瓦斯浓度相 对较低,说明抽放效果不错,达到预期的目的,但要 特别注意进风侧的下隅角,该处可能会有瓦斯积聚。 从图5可以看出,采空区下部的瓦斯浓度明显高于 上部的瓦斯浓度;对从现场瓦斯抽放口采集的气体 进行了化验,其结果和模拟结果一致。 2. 3 采空区氧气浓度分布规律 采空区氧气浓度分布如图67所示,可以看 出,采空区氧气浓度在距工作面较近处较高,距离工 作面越远则氧气浓度越低。在抽放口附近氧气浓度 降低较慢,这是由于大量气体从该处抽出,影响了气 体的正常渗流,促使在距离工作面水平距离相同的 条件下,回风巷侧的氧气浓度相对高于进风巷侧的 氧气浓度。 图4 水平剖面瓦斯浓度分布 图5 垂直剖面瓦斯浓度分布 图6 水平剖面氧气浓度分布 图7 垂直剖面氧气浓度分布 2. 4 采空区漏风强度分布规律 漏风强度分布规律如图89所示,可以看出, 漏风强度在回风巷出口和抽放口处最大,而回风侧 的漏风强度也比进风侧大。从图9还可以看出,采 空区底部的漏风强度远大于采空区上部,这也解释 了为什么火灾多发生在支架顶部位置,因为此处有 较好的热量积聚条件足够的氧浓度、 适当的漏风强 度和浮煤厚度。 11 2009年2月 矿业安全与环保 第36卷第1期 1994-2010 China Academic Journal Electronic Publishing House. All rights reserved. 图8 水平剖面漏风强度分布 图9 垂直剖面漏风强度分布 3 工作面采空区自燃 “三带” 划分 根据模拟结果及煤自然发火实验结果,可以得 到采空区不同位置的氧气浓度和漏风强度的分布情 况。将煤层中水平面水平方向坐标相同,垂直方向 不同的点中氧气浓度值和漏风强度值绘制成等值 线,将其绘制在同一张图上,可得到如图10所示的 采空区自燃 “三带” 划分图。漏风强度等于极限漏风 强度的曲线对应于散热带和氧化升温带的边界,氧 浓度等于极限氧浓度的等值线也就是窒息带和氧化 升温带的边界 [5 - 6] 。图中极限氧气浓度为φmin,极限 渗流速度为Vmax均由煤自然发火实验测得的点对 应的水平距离即为氧化升温带宽度。该工作面采空 区浮煤厚度平均为4. 10 m ,其中两巷道处厚达9 m , 根据该煤矿煤样自然发火实验,4. 10 m的浮煤厚度 远远超过煤自燃的极限浮煤厚度hmin,给工作面采 空区的浮煤自燃创造了极为有利的条件。 图10 采空区自燃 “三带” 划分图 从图10可以看出,带抽放口的整个综放工作面 都存在氧化升温带,在工作面进风侧,氧化升温带宽 约为55 m ,该处窒息带深约80 m ,散热带深约15 m。 在距离工作面回风侧20～30 m处氧化升温带 也达到一个最大值此处为自燃危险区 , 对应氧化 升温带宽度约为85 m ,该处窒息带深度约40 m ,散热 带深度约25 m。 4 综放面极限推进速度确定 综放采空区散热带到采空区窒息带的最大距离 即氧化升温带最大宽度Lmax 85 m。根据现场监 测的氧气浓度可求出采空区进风侧至窒息带范围内 平均氧气体积分数为16 ,则实验氧气的体积分数 与实际氧气的体积分数相似比例系数 [5]κ φ新O 2 φO 2 21 16 1. 3φ新O 2为新鲜风流氧气浓度 ,取21 。以 采空区平均温度为30℃ 计,采空区浮煤最短自然发 火期τmin 43 d 煤自然发火实验测得 , 根据文献 [2]可知,采空区可能发生自燃的工作面极限推进速 度为 vmin Lmax τminκ 85 431. 3 1. 5 mΠd 因此,当采煤工作面的推进速度大于1.5 mΠd时, 采空区无自然发火危险;当工作面连续超过43 d推进 速度均小于1.5 mΠd ,采空区将有自然发火危险。 21 2009年2月 矿业安全与环保 第36卷第1期 1994-2010 China Academic Journal Electronic Publishing House. All rights reserved. 5 结论 工作面风量、 煤的耗氧速率、 煤自燃的极限参数 和松散煤体的孔隙特性等对采空区 “三带” 的分布都 有影响。通过数值模拟综放工作面采空区漏风状 况,得到高瓦斯煤层抽放条件下综放工作面采空区 自燃 “三带” 的分布规律及其自燃的可能性,根据现 场实际条件和模拟结果,可得出以下结论 1 抽放瓦斯条件下,采空区氧气浓度在距工作 面较近处较高,距离工作面越远则氧气浓度越低,当 采空区达到一定深度时,氧气的体积分数迅速降低 到5 以下。在抽放口附近氧气浓度降低较慢,这是 由于大量气体从该处抽出,影响了气体的正常流动, 促使回风侧采空区内的氧浓度比同位置进风侧采空 区内的氧浓度高。 2 抽放瓦斯条件下,采空区漏风自工作面进风 侧流入,从距离工作面回风侧30 m处的瓦斯抽放 口、 回风巷和回风侧采空区抽放口流出。靠近回风 侧压力低,而进风侧压力相对较高。 3 实施抽放后,靠近进风巷侧的瓦斯浓度相对 较高,采空区回风巷侧瓦斯浓度相对较低,说明抽放 效果明显,抽放口的位置和抽放量的设计达到了预 期的效果,确保了在高瓦斯煤层中综放开采的顺利 进行,但要注意进风巷侧瓦斯浓度相对较高,有可能 超限。 4 抽放条件下,漏风强度在抽放口处最大,在回 风巷侧相对比进风巷侧大一些,工作面回风巷处漏 风强度也较大,在抽放口附近,已具备煤自燃充要条 件,要及时防止在此类地区出现浮煤自燃。 参考文献 [1]孔祥言.高等渗流力学[M].北京中国科学技术大学出 版社,1999. [2]韩占忠,王敬,兰小平.流体工程仿真计算实例与应用 [M].北京北京理工大学出版社,2004. [3]陈明河.高瓦斯煤层抽放条件下综放采空区自燃预测研 究[D].西安西安科技大学,1997. [4]张国枢,谭允祯,陈开岩,等.通风安全学[M].徐州中国 矿业大学出版社,2003. [5]徐精彩.煤自燃危险区域判定理论[M].北京煤炭工业 出版社,2001. [6]徐精彩,张辛亥,文虎,等.煤层自燃胶体防灭火理论与 技术[M].北京煤炭工业出版社,2003. 责任编辑卫 蓉 上接第9页 线分布。当原始瓦斯压力不同时,瓦斯流动范围内 的压力梯度不同。原始瓦斯压力越高,流场中的瓦 斯压力梯度越大,而根据氏平 [11]的试验研究结果 ,瓦 斯压力梯度是导致煤体拉应变增高从而引起煤体失 稳的直接原因。这说明在煤层物理条件相同的情况 下,原始瓦斯压力越高,煤层开采的危险性就越大。 3 结论 1 建立了计算裂隙煤体内瓦斯压力的LBM动 力学模型,自主开发数值计算程序,模拟了煤层瓦斯 压力在时间和空间上的分布规律。 2 模拟结果表明瓦斯压力分布与煤壁暴露的时 间和煤体所处的空间位置有关。煤壁的暴露时间越长, 煤壁处的瓦斯压力梯度越小,流场内瓦斯压力的变化范 围越大。在空间上瓦斯压力呈二次曲线分布。 3 根据模拟的瓦斯压力在时间和空间上的分 布情况,可以确定每天的采煤速度,为安全生产提供 依据。 参考文献 [1] Ren T X, EdwardsJ S, DavidJ. Simulation of methane drain2 age boreholes using computational fluid dynamics[J ]. American Society of Mechanical Engineers Pressure Vessels and Piping Division ,1999 , 397319 - 326. [2]朱诗山,刘向阳.低透气性薄煤层瓦斯抽放方法[J ].煤 炭技术,2003 ,228 75 - 76. [3]李宗翔.综放工作面采空区瓦斯涌出规律的数值模拟研 究[J ].煤炭学报,2002 , 272 173 - 178. [4] Spaid MAA , Phelan FRJ. Lattice Boltzmann for model2 ing micro - scale flow in fibrous porous media [J ]. Physical Fluids ,1997 , 9 2468 - 2474. [5]陶果.岩石物理的理论模拟和数值实验新方法[J ].地 球物理进展, 2005 , 201 4 - 11. [6] Shiyi Chen , Gary D Doolen. Lattice Boltzmann for fluid flows[J ]. Fluid Mech. , 1998 , 30 329 - 364. [7] Guo Z- L , Shi B - C, Wang N - C. Lattice BGK model for incompressible Navier - Stokes equation [J ].Computation Phys , 2000 , 165288 - 306. [8] Succi S, Foti E, Higuera F. Three dimensional flows in com2 plex geometries with the Lattice Boltzmann [J ]. Europe phys , 1989 , lett.10 433 - 438. [9] Y. H.Qian , D. d’Humieres , P.Lallemand. Lattice BGKmod2 els for Navier - Stokes equation[J ]. Europe Phys , 1992 , Lett 479 - 484. [10] Zhaoli Guo. Lattice Boltzmann model for incompr - essible flows through porous media[J ]. The American Physical Soci2 ety ,2002 , 663 36304 - 1 - 9. [11]氏平增之,刘冠玉.瓦斯突出危险区域的爆破[J ].矿业 安全与环保,19895 46 - 53. 责任编辑卫 蓉 31 2009年2月 矿业安全与环保 第36卷第1期 1994-2010 China Academic Journal Electronic Publishing House. All rights reserved. Vol.36 No.1 2009MINING SAFETY the activation energy E and the pre - exponential factor A at different temperature stage were also calcu2 lated by slope and intercept. In particular , the relation between activation energy E and temperature T and reaction velocity and the ation of negative activation energy for Chaili gas coal were explained according to T olman’s definition on acti2 vation energy E. Studyon Distribution Regularity of Coal - body G as Pressure near Coal Draw - point in Early Stage of Caving Mining4 - The gas migration in coal body infront of the fully mechanized cavingface mainly seepages along the coal seam surface to the mined - out space. When a fully mechanized caving face is cyclically ad2 vanced forward , the structure of the seepage fieldof coal body gas changed. Simu2 lation analysis was made on the gas pressure near the fully mechanized cavingface by using ANSYS10.0 transient analysis module in order to further probe into the variation regularity of gas pressure distribution in the coal body infront of the fully mechanized caving face and effectively control the gas. Study indicated that the varying gradient of gas pressure in the stress - lowering zone in front of the fully mechanized caving face is large , but in the stress - increasing zone , the gas pres2 sure is relatively high and the varying gradient of gas pressure is small ; the gradi2 ent of gas pressure ed in the first coal - caving cycle in front of the face is larger than that in the second coal - caving cycle. Simulative Study on G as Pressure Distribution Based on Lattice Boltzmann 7 - A new dynamic model for the simulation of two - dimensional gas pressure in fissured coal was established based on Lattice Boltzmann LBM , and simulation study was made on the spatial distribution and time evolvement of gas pressure , the simulation results indicated that the gas pressure distribution is relat2 ed to the exposure time and the position of coal wall ; the longer the exposure time of coal wall , the smaller the gas pressure gradient at the coal wall and the larger the variation range of gas pressure in gas flow fluid. The spatial gas pressure was in a quadratic curve distribution. The simulation results are consistent with the theoretical analysis and experimental results. This showed that LBM is a new cal2 culation for studying gas migration regularity in coal seam. Simulation and Analysison Breathingof G ob10 - Based on the establishment of three - dimensional spontaneous combustion prediction model for the gobof fully - mechanized caving face , numerical simulation on the breathing of the gob of fully - mechanized caving face of high - gassy coal seam was conducted by using nu2 merical simulation software under gas drainage condition ,“Three - zones”of spontaneous combustion of coal were divided according to the simulated results , and the dangerous zone and degree of spontaneous combustion of float coal in the gob of thisface were also analyzed , which can be used to guide the prevention and control work of spontaneous combustion of float coal in the gob of the face with similar conditions. Comparative Study on Surface Subsidence Prediction Based on BP - ANN M odel 17 - Based on comprehensive analysis of the factors influencing surface subsid2 ence , a prediction model for surface subsidence was established by different meth2 ods of back propagation artificial neural network BP - ANN . A large amount of data obtained at observation stations in a mining field was used for training and perance test of BP - ANN models , and comparison and analysison these mod2 els were made. The results indicated that it is much more reasonable to use BP - ANN model to predict the mining subsidence. The limited artificial factors during the prediction , simplified the complexproblems and made the solution more reasonable and creditable. So , it has a certain application value. uation of Mine Ventilation System Based on Gray Cluster Analysis and Fuzzy Comprehensive uation26 - Based on extensive investigation and analysis of main factors influencing the running of mine ventilation system , a comprehensive uation index systemfor mine ventilation systemwas constructed by utilizing the principle and of multi - objective decision - marking theory. And a com2 prehensive uation model for mine ventilation system was established by using the gray cluster analysis in gray theory and the fuzzy comprehensive uation , this thus quantitatively solved the uation grade of the ventilation effect of mine ventilation system. In this paper , uation was made by taking Tangs2 hangou Coal Mine as an example , and the uation results were consistent with the actual survey. Application of Isotopic Technique in Identification of Mine Water Inrush Source 32 - The application of isotopic technique can get critical data which can’t be obtained by conventional , this thus plays an important role for the analysis of supply source of underground water , the linkage between each water - bearing beds, the age and the mixing proportion of underground water and so on. The study results showed that the application of this technique can accurately and rap2 idly determine the isotopic characteristics of underground water and identify the main source of mine water inrush. The application of this technique can provide scientific basis for the working - out of effective mine water prevention and control s. Study of Coal Mine Emergency Rescue Ination Management System Based on NET Plat35 - The traditional coalmine emergency rescue ination system based on CΠS structure has some disadvantages such as miscellaneous program2 ming , connatural hidden trouble and low efficiency , so a of system design and realization based on BΠS structure was put forward. This system runs on Mi2 crosoft. NET plat which uses SQL Server 2003 as database server and ASP. NET environment for programming. It uses ADO. NET, the subassemblyof ASP. NETto access the database. which makes the system reliable , efficient , conve2 nient and easy to maintain. The practice showed that the system is helpful and universal. Application of Matter - Element M odel in uation and Prediction of Seam Roof Stability38 - In this paper , a stability identification and prediction model for coal seam roof was established and the mater - element correlative function for the stability uation of coal seam roof and the calculation for mater - ele2 ment correlative degree were given according to some factors influencing the stabil2 ity classification of coal seam roof and by applying the matter - elements model in order to accurately predict the stability of coal seam roof. The classification stan2 dard suitable for prolongable theory for stability grade of coal seam roof was also established , which employed the complex weight of inds and made full use of the ination obtained by the subjective objective favoritism. The application re2 sults indicated that this model is suitable for the identification and uation of coal seam roof stability. Study on Construction of Early Warning System of Floor Water Inrush in Mine W orking Face58 - Starting from correlative concepts about floor water inrush in the working face and based on the analysis of various factors influencing mine wa2 ter inrush , this paper described the function and significance of constructing early warning system of floor water inrush. By taking the early warning theory as the guide and according to the actual requirements for mine water hazard prevention and control , an early warning system of floor water inrush was constructed , this paper put forward the logic structure and overall framework of this system and ana2 lyzed the function of its main composing layers. So it provided a new scheme for building the early warning system of floor water inrush.