关键词: 三维交叉裂隙, 渗流特性, 传质特性, Navier-Stokes方程, 佩克莱数

Abstract: Quantitative description of fluid flow and solute transport properties of crossed fractures is a fundamental issue for understanding the characteristics of fracture networks. This study is aimed to simulate the fluid flow and solute transport through three-dimensional crossed fractures. The morphological data of the natural rock fracture surface was first obtained via a three-dimensional profilometer, and then a reconstruction technique was employed to generate the corresponding three-dimensional crossed fracture model. The Navier-Stokes equations were solved to simulate the fluid flow and solute transport through the intersection by assuming the solute transport satisfying the Fick’s law. Comparing the simulation results of the rough-walled model with the parallel-plate model, it was found that the surface roughness had a significant influence on the distribution and flow state of the fluid through the intersection. The results obtained from different inlet and outlet configurations showed that the geometry of intersection greatly affected the solute mixing process. These results revealed that the widely accepted parallel-plate model led to remarkable errors in the assessment of solute transport behaviour in fractured rock masses, especially the intersections. Therefore, it is necessary to establish modified models to improve the accuracy of the assessment in future studies.

Key words: 3D crossed fractures, fluid flow behaviour, solute transport behaviour, Navier-Stokes equation, Peclet number