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构造区回采煤层瓦斯迁移规律分析

Analysis of gas migration law in coal seam in structural zone

  • 摘要: 煤与瓦斯突出是煤层资源回采过程中一种常见的动力灾害,严重影响着生产作业的安全,而构造区则是煤与瓦斯突出灾害发生的主要区域。为了深入了解构造区煤与瓦斯突出的作用机理,以大平煤矿吴庄逆断层为研究主体,通过COMSOL数值模拟软件,建立了包含断层构造的二维矿山地质模型。然后将固体力学与达西定律模型进行耦合,对距离断层不同距离回采时煤层工作面的地应力、瓦斯压力分布和瓦斯迁移规律进行了研究。研究结果显示:①当回采工作面距断层450 m时,工作面应力提升为原岩应力的两倍,瓦斯流动状态为层流,在工作面前方20 m处瓦斯压力最大;②当回采工作面距离断层50 m时,工作面应力提高为原岩应力的3倍以上,瓦斯流动状态由层流变为紊流,工作面前方30 m范围内瓦斯压力均处于较高值;③回采结束后,瓦斯渗流速度迅速增大,在1 h后达到渗流速度达到最大,此时为煤与瓦斯突出灾害发生的高风险时间段,随后渗流速度将逐渐降低,突出风险也逐渐降低。因此为了保证回采的安全性,不仅要在回采前通过煤层注水、预掘疏压硐室等方式降低煤层应力状态,且需要采用水力冲孔、瓦斯抽采或其他有效方式降低瓦斯压力。通过对回采后煤层瓦斯迁移规律的研究,可以对通风设计与煤与瓦斯灾害防治提供有效的依据。

     

    Abstract: Coal and gas outburst is a common dynamic disaster in the process of coal seam resource recovery, which seriously affects the safety of production operations, and the tectonic zone is the main area where coal and gas outburst disasters commonly occur. In order to deeply understand the mechanism of coal and gas outburst in the structural area, taking the Wuzhuang reverse fault in Daping Coal Mine as the main research body, a two-dimensional mine geological model including the fault structure was established through the COMSOL numerical simulation software. Then the solid mechanics and Darcy’s law model were coupled to study the in-situ stress, gas pressure distribution and gas migration law of the coal seam working face at different distancesfrom the fault. The results of the study show that ① when the working face is 450 m away from the fault, the stress of the working face increases to twice the stress of the original rock, the gas flow state is laminar flow, and the gas pressure is 〖JP2〗the largest at 20 m in front of the working face; ② When the working face is 50 m away from the fault, the working face stress is increased to more than three times that of the original rock, the gas flow state changes from laminar flow to turbulent flow, and the gas pressure within 30 m infront of the working face is at a high value; ③ After mining, the gas seepage velocity increases rapidly and reaches the maximum after 1 h, which is a high-risk time period for coal and gas outburst disasters, and then the seepage velocity will gradually decrease and the risk of outburst will gradually decrease. Therefore, in order to ensure the safety of recovery, it is important to not only reduce the stress state of the coal seam by water injection and pre-excavation of pressure relief chambers prior to recovery, 〖JP2〗but also to reduce the gas pressure by hydraulic punching, gas extraction or other effective means. By studying the gas migration law in coal seams after mining, it can provide an effective basis for ventilation design and prevention of coal and gas disasters.

     

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