Characteristics of Fluid Flow and Solute Transport in Multicrossed Rough Rock Fractures Based on Three-Dimensional Simulation

Abstract

Fluid flow and solute transport in rock fractures are important for controlling pollutant migration in groundwater and radionuclide migration in nuclear waste disposal. The quantitative characterization of fluid flow and mass transport in crossed fractures is the key to defining solute transport in a fracture network. In this study, the characteristics of fluid flow and solute transport in rock fractures were investigated through experiments and simulation. The surface topography of these fractures was reconstructed using 3D laser scanning technology. The solute transport in crossed parallel plates and rough fractures with intersecting angles of 30°, 60°, 90°, 120°, and 150° was investigated under different initial conditions. Results show that the intersection angle and fluid velocity significantly affect the fluid flow pattern at the intersection. As the flow velocity and intersection angle increase, streamlines at the intersection of rough fractures are unevenly distributed. The fluid tends to seep into the dominant channel and has different degrees of channeling flow at the intersection of fractures. An eddy phenomenon is observed at the intersection, indicating that the seepage behavior transforms into a non-Darcy flow. As the Peclet number (Pe) increases, solute migration and diffusion gradually decrease; however, the convection part gradually increases. Thus, the solute transport mode gradually changes into a streamline path mode at the intersection of fractures.