考虑基质渗透性的裂隙岩体 REV 变化机制研究

表征单元体（representative elementary volume, REV）的存在是使用等效连续方法的前提。文章基于三峡工程收集的裂隙几何参数，利用蒙特卡洛方法对裂隙岩体进行20次随机模拟，基于COMSOL Multiphysics的数值模型对裂隙岩体进行数值建模，从生成的裂隙岩体几何模型中提取不同尺寸的计算域（边长为6～70 m，每次间隔4 m），在不考虑基质渗透性和考虑基质渗透性情况下，计算不同尺寸的裂隙岩体渗透率大小，探究渗透率REV随裂隙隙宽的变化规律。研究结果表明：不考虑基质渗透性时，REV与裂隙隙宽无关；考虑基质渗透性时，REV随裂隙隙宽的增大呈现增大趋势；考虑基质渗透性且裂隙隙宽很小时，裂隙网络更倾向为均质介质，REV很小，裂隙隙宽越大，流场非均质性越强，REV也随裂隙隙宽增大而增大。该研究拓展了裂隙岩体的等效性范围，为考虑基质渗透性时的裂隙岩体渗流研究提供了参考。

The existence of the representative elementary volume (REV) is a prerequisite for using the equivalent continuum methods. This paper utilized the geometric parameters of fractures collected from the Three Gorges Project and conducted 20 random simulations of fractured rock masses using the Monte Carlo method. A numerical model of fractured rock masses was established based on COMSOL Multiphysics. Different-sized computational domains (ranging from 6 to 70 m with a 4-m increment) were extracted from the generated geometric model of fractured rock masses. The permeability values of fractured rock masses of different sizes and the variation pattern of permeability REV with changes in fracture aperture were calculated with and without consideration of matrix permeability. The research findings indicate that when matrix permeability is not considered, REV is independent of fracture aperture; when matrix permeability is considered, REV tends to increase with the enlargement of fracture aperture. In cases where matrix permeability is considered and fracture apertures are small, the fracture network tends to behave as a homogeneous medium with a small REV. As the fracture aperture increases, the heterogeneity of the flow field becomes stronger, and REV also increases. This study expands the range of equivalency for fractured rock masses and provides reference for studying fluid flow in fractured rock masses when considering matrix permeability.