In study of gas migration process in coal seam, the permeability evolution rule with time has been one of hot topics in the area of coal seam for decades. At present, in view of the time-varying rule of coal seam permeability, the influence of microstructure parameters and adsorption effect are seldom considered simultaneously. In this paper, the fractal seepage model coupled with coal deformation, and the adsorption expansion effect of coal is proposed. A multi-field coupling model is established by considering the influence of matrix and fracture structure. The influence of structural parameters and adsorption constant of main fracture on the time-varying curve of macro permeability are analyzed, including: (1) fractal dimension for fracture lengths; (2) maximum fracture length; (3) Langmuir adsorption strain constant; (4) Langmuir adsorption pressure constant. The results show that, under the influence of in situ stress and adsorption effect, the permeability of coal seam decreases with time. The present results show that the permeability is proportional to the fractal dimension for fracture lengths and the maximum fracture length. The uniformity of permeability distribution is found to be directly proportional to the pressure constant of Langmuir and inversely proportional to the volume constant of Langmuir.

中文翻译：

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基于双分形耦合模型的煤层渗透率演化特征分析

在煤层瓦斯运移过程研究中，渗透率随时间演化规律是几十年来煤层领域研究的热点之一。目前，鉴于煤层渗透率的时变规律，很少同时考虑微观结构参数和吸附效果的影响。本文提出了与煤变形耦合的分形渗流模型，以及煤的吸附膨胀效应。考虑基质和裂缝结构的影响，建立了多场耦合模型。分析了构造参数和主裂缝吸附常数对宏观渗透率时变曲线的影响，包括：（1）裂缝长度分形维数；(2) 最大断裂长度；(3) Langmuir吸附应变常数；(4)朗缪尔吸附压力常数。结果表明，在地应力和吸附作用的影响下，煤层的渗透率随时间降低。目前的结果表明，渗透率与裂缝长度的分形维数和最大裂缝长度成正比。渗透率分布的均匀性与朗缪尔压力常数成正比，与朗缪尔体积常数成反比。