综采工作面上隅角瓦斯流动活跃区形成机理研究

Study on formation mechanism of gas flow active area in upper corner of fully-machanized mining face

为解决综采工作面回采期间上隅角瓦斯超限问题,以山西某高瓦斯矿井主采工作面为原型,基于物理相似模拟试验,采用分形理论从细观角度证实了瓦斯流动活跃区的存在性,通过构建瓦斯流动活跃区的空间模型和力学模型,研究了工作面上隅角瓦斯流动活跃区的形成机理,并结合FLUENT数值模拟软件,对上隅角埋管抽采瓦斯的布置参数进行了优化。结果表明:通过对比局部瓦斯优势通道裂隙网络与整体覆岩裂隙网络的分形特征,认为局部裂隙网络发育更为丰富,进而证实了瓦斯流动活跃区的存在;推导出了瓦斯流动活跃区关键岩块的二次失稳形式及判据,认为关键岩块不会发生二次失稳,保证了关键岩块的存在,从而保证了瓦斯流动活跃区不会消失,为上隅角埋管抽采活跃区瓦斯提供了可稳定参考的位置基础;通过对埋管深度为5、15、25 m时采空区及工作面的瓦斯浓度分布进行数值模拟,认为埋管深度为15 m时的抽排效果最佳。

In order to solve the gas overlimit problem in the upper corner during the mining process of the fully-mechanized coal mining face,with the major coal mining face in a high gassy mine in Shanxi as the model,based on the physical similar simulation test,a fractal theory was applied to prove the existence of the gas flow active area from a view of mesoscopic point. A space model and a mechanics model of the gas flow active area established were applied to study the formation mechanism of the gas flow active area at the upper corner of the coal mining face,and in combination with the FLUENT numerical simulation software,an optimization was conducted on the layout parameters of the gas drainage with the pipe buried at the upper corner. The result showed that with the comparison on the fractal features between the crack network of the local gas dominant channel and the crack network of the integrated overburden strata,the development of the local crack network considered was abundant and the existence of the gas flow active area was proved. The second unstable mode and criteria of the key rock block in the gas flow active area were deduced. The paper held that the key rock block with no second unstability occurred could ensure the existence of the key rock block,thus could ensure the gas flow active area without a disappearance occurred and could prove a stable reference location base to the gas in the gas drainage area with the pipe buried in the upper corner. When the pipe buried depth was 5 m,15 m and 25 m,a numerical simulation was conducted on the gas concentrations distribution in the goaf and the coal mining face. The paper held that the gas drainage effect was the best when the pipe buried depth was 15 m.