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采用渗流力学理论并结合Monte Carlo方法描述岩体裂隙的随机分布,研究渗流模型的尺寸效应并确定表征单元体积(REV),得到了3种开口度分布形式的等效渗透系数椭圆曲线,建立了等效渗透系数方向性的判别标准。离散裂隙网络(DFN)模型假定流体只在岩体裂隙内部流动,而不通过岩体本身渗流。基于二维离散元程序UDEC并进行二次开发,建立DFN模型,通过改变流体的流动方向,得到不同流动方向下岩体裂隙网络的等效渗透系数,并分析不同的开口度分布形式对岩体裂隙网络等效渗透系数方向性的影响。计算结果表明,表征单元体积存在的条件是等效渗透系数保持稳定且渗透椭圆比较光滑。等效渗透系数的方向性受开口度分布形式的影响很大:当开口度-长度关联分布时,等效渗透系数各向异性;当开口度对数正态分布时,等效渗透系数各向同性;当开口度恒定分布时,等效渗透系数的特性介于二者之间。变化系数(CV)是否大于5%是判定岩体裂隙网络渗透系数是否具有方向性的判别标准。
The seepage mechanics theory and the Monte Carlo method are used to describe the random distribution of rock mass fissures. The size effect of the seepage model is studied and the characterization unit volume (REV) is determined. Three kinds of equivalent permeability coefficient elliptic curves in the form of open degree are obtained, Equivalent permeability coefficient of the criterion of discrimination. The Discrete Fissure Network (DFN) model assumes that fluids flow only inside the rock mass fissures and not through the rock mass itself. Based on the two-dimensional discrete element program UDEC and its secondary development, the DFN model is established. By changing the fluid flow direction, the equivalent permeability coefficient of rock fracture network under different flow directions is obtained. The influence of different open degree distribution on rock mass The effect of the equivalent permeability coefficient of fracture network on directivity. The calculation results show that the conditions for the existence of the characterizing unit volume are that the equivalent permeability coefficient remains stable and the osmotic ellipse is relatively smooth. The directivity of the equivalent permeability coefficient is greatly affected by the distribution of the opening degree: when the opening-length correlation distribution, the equivalent permeability coefficient is anisotropic; when the opening degree is log-normal distribution, the equivalent permeability coefficient is Same sex; When the opening degree of constant distribution, the equivalent permeability coefficient between the two characteristics. Whether the coefficient of variation (CV) is greater than 5% is the criterion for determining whether the permeability coefficient of rock fracture network has directionality.