非均质各向异性三维动态采空区渗透系数反演研究

The trial calculation method on the basis of artificial experience is still used for the solution of the permeability coefficients of the coal goaf. It is a bottleneck for studying the problem of the goaf seepage. On the basis of the elements that the different regions of coal goaf automatically are divided into in the project, the mechanism of DNA coding and decoding is studied for the inversion of the permeability coefficients of 3D inhomogeneity anisotropic coal goaf by genetic algorithm, and the optimized model the reproduction, crossover and mutation operators is proposed for solving the problem of huge calculation. Therefore, the algorithm which inverses the permeability coefficients is put forward by the means of the genetic program and genetic algorithm, and the test standard of the algorithm is proposed. According to the definition of the representative elementary unit, the measured values of gas concentration are introduced into the fitness function by the coupling mechanism of solving filtration equation and dispersion equation for solving well the problem of false convergence because of the lack of boundary condition. Meanwhile, A solution of filtering, which can solve the noise aroused by the discreteness of the permeability coefficients distribution and the insensitivity between the stiffness matrix and system stiffness matrix of finite element, is presented. The research results are of important theoretical meaning and practical value for studying the flow field of coal goaf.

目前采空区渗流系数解决方法基本停留在人工经验的试算基础之上，这成为了采空区渗流研究领域的瓶颈之一。本项目在三维动态采空区自动剖分基础上，通过对基于遗传算法的非均质各向异性三维动态采空区渗透系数反演的DNA编码及解码机制，基于遗传规划的复制、交叉、突变算子优化模式解决渗透系数反演的海量计算问题的研究，完成一套基于遗传规划与遗传算法的反演三维非均质各向异性采空区渗透系数的算法及实验检验标准。项目在论证表征体元概念的基础上，引入弥散方程耦合求解机制，将采空区内部组分气体浓度实测值加入适应函数的适应度计算，解决边界条件不够所带来的假收敛问题，同时提出了相应的滤波解决方案来解决反演渗透系数时由遗传算法中带来的单元渗透系数分布的离散性及有限元法中单刚矩阵对总刚矩阵的不敏感性引起的噪声。项目成果对采空区流场研究具有重要的理论意义和实用价值。

煤矿井下采空区空间构成复杂多变，其渗流场域参数的改变，直接影响到渗流流场的改变，从而影响到采空区内煤自燃三带分布及其它采空区灾害的形成和防治。因此，对采空区内渗流场域、渗透系数及其特性的研究显得尤为重要。.项目研究结合实际矿井情况，采取理论分析、实验研究、数值模拟和现场试验相结合的研究方法，开展了以下研究：采空区渗流场域的形成特征及影响因素分析；采用遗传算法对非均质各向异性三维动态采空区渗透系数反演的DNA编码及解码机制进行研究；将煤壁支撑影响区域内的冒落煤岩体视为自由堆积体多孔介质，利用自制模型，对自由堆积体均质、非均质多孔介质进行了渗流实验研究，探究渗流速度、渗流压力梯度与介质粒径大小的关系，渗流状态转变的渗流速度阈值；建立采空区三维渗流模型，进行了工作面阻力分布对工作面两端压差、采空区内渗流压力的影响实验；利用CFD软件分析了综放工作面采空区的渗流规律；最后，通过以铁法大兴煤矿为例，通过现场实测数据的分析，验证了实验规律和数值模拟规律的正确性。.研究结果表明：在相同渗透速度变化范围内，随着构成多孔介质“骨架”颗粒粒径的增加，渗透的压力梯度降低，渗流状态逐步由以粘性力为主的线性渗流向以惯性力为主的非线性渗流转变，且转变的渗流速度阈值逐步减小；非均质多孔介质中的渗透系数和渗流状态转变的渗流速度大小主要取决于其小粒径颗粒所占的比例；在相同地质条件下，随着综放工作面采放比的增加，采空区渗流场域在走向上减小，高度增加；采空区内渗流速度场分布具有较弱的对称性，进风隅角和回风隅角在相同速度区间内，回风侧渗流范围大于进风侧渗流范围，走向上，过渡渗流（非线性渗流）区域均出现减小的趋势，倾向上，过渡渗流（非线性渗流）区域增加。遗传算法分析结果与实测分析、模拟结果具有较好的一致性。研究成果获中国煤炭学会科技成果三等奖。