Impact of shear process on solute transport and mixing partitioning in 3D intersecting fractures of thermally shocked granite

The shear process of fractures is a critical indicator affecting permeability and heat-mass transfer behavior in deep geothermal reservoirs. This study examines solute transport in thermally shocked intersecting fractures during shearing. Using Particle Flow Code (PFC), we examined the mesoscopic thermal damage mechanisms in granite single-fracture specimens subjected to differential thermal shocks. Finite-element simulations with COMSOL Multiphysics were then conducted to model solute transport in thermally shocked intersecting fractures during shearing, with a focus on solute mixing and partitioning at the fracture intersections. The results show that the mixing-partitioning pattern of solutes at fracture intersections during shear depends primarily on shear-induced dilations, which alters geometric configurations and solute transport mechanisms. The resulting mixing-partitioning pattern stems from the coupled interaction of these transport mechanisms with the dynamically evolving intersection geometry. Based on this, we developed an empirical formula that effectively quantifies the mixing-partitioning regimes in sheared, thermally shocked intersecting fractures under different flow conditions across the linear flow regime spectrum.