基于sigmoid函数的采空区渗透率模型及瓦斯流场模拟应用

Permeability model of gob based on sigmoid function and application in the airflow field simulation

为研究综放工作面的高抽巷对采空区瓦斯流动的控制作用,基于sigmoid函数建立了采空区三维非均质渗透率模型,模型参数能够反映采空区分区、分带特性。以塔山煤矿特厚煤层厚硬顶板条件下的综放工作面为工程背景,由于缺乏"三带"高度经验公式,离散元程序被用于研究其采空区分区、分带特性。通过模型对比和现场监测,分析了采空区渗透率模型的准确性,并结合CFD模拟研究了高抽巷对采空区内流态和瓦斯浓度分布的影响。结果表明,厚硬顶板综放开采条件下运用离散元模拟比综采经验公式得到的"三带"结果更为准确;建立的渗透率模型准确可靠,能真实反映采动覆岩的形态特征;高抽巷导流能消除隅角瓦斯超限危险。

In order to study controlling effect of high level gas drainage roadway on gas flow in a fully mechanized top-coal caving （FMTC） face, a three-dimensional and heterogeneous permeability model on the basis of sigmoid function is established in which the parameters are linked to zoning characteristics or belting characteristics of gob. Taking a FMTC face which is situated within ultra-thick seam with hard-thick roof of Tashan coal mine as an engineering case, due to the lack of corresponding empirical formula for computing heights of ＂three zones＂, the discrete element method is used in studying its zoning and belting characteristics. The accuracy of the established model is analyzed by comparison of different model and field data. In addition, CFD simulation is utilized to study the impact of high the high level gas drainage roadway on the flow pattern and the gas concentration distribution in gob. The results show that the division of ＂three belts＂ is more accurate by applying discrete element method than the empirical formula calculations for the FMTC face. The permeability model in this paper is accurate and reliable which can really reflect morphological characteristics of the mining strata, the gas over limit can be eliminated by using the high level gas drainage roadway.