The influence of geometric characteristics of intersecting fractures in rock mass on solute transport

The solute transport characteristics of intersecting fracture are the basis of solute transport in fracture network of rock mass. Advection and hydrodynamic dispersion are the main control mechanisms of non-reactive solute transport, and Péclet number is used to evaluate the proportion of influence of both on non-reactive solute transport. In this paper, by changing the flow velocity of the injected fluid, changing the geometric characteristics of the intersecting fracture, such as roughness, intersecting angle and aperture ratio, the influence of Péclet number and intersecting fracture geometric characteristics on the solute transport characteristics is obtained by finite element numerical analysis. The findings indicate that increasing flow velocity shifts solute transport from dispersion to advection. By comprehensively considering the dispersion effect in practical engineering, it is beneficial for accurately evaluating the mixing degree of solute at the intersection. Roughness primarily affects solute migration time towards outlets, while intersecting angle and aperture ratio significantly influence mixing at intersections by affecting probability of diffusion to different outlet branches and fluid flow patterns towards these branches. Different flow ratios also affect intersection mixing by influencing dominant flow positions towards exit branches. The research conclusions can provide a theoretical basis for the prevention and control of groundwater pollutants in underground engineering such as oil and gas underground storage, landfill, and nuclear waste disposal.