Predictive model of solute transport processes in fractured rock based on geometric features

The mechanisms and predictive modeling of solute transport in fractured rocks represent a frontier and hotspot in the fields of hydraulic rock mechanics and hydrogeology. They also address critical scientific challenges, including pollution remediation in fractured bedrock aquifers, safe disposal of high-level radioactive waste, efficient underground resource extraction, leakage tracing, and the interpretation of chemical signals associated with geohazards. This study simulates solute transport processes under various fracture network geometric characteristics, systematically analyzing the quantitative control mechanisms of fracture density, fracture discreteness, and mean fracture aperture on solute transport. The results indicate that fracture density and mean aperture are decisive factors in controlling solute transport, while the influence of fracture distribution discreteness depends on the connectivity of pathways formed by specific fracture networks. Based on these findings, parameterization formulas for key transport coefficients—hydrodynamic dispersion coefficient (D) and solute transport velocity (Vt)—were developed using dimensionless fracture density and mean aperture. These formulas were incorporated into the classical macroscopic advection–dispersion analytical solution to construct a predictive model for solute transport processes based on fracture network geometric parameters. Comparison with numerical simulation results under various conditions validated the model's accuracy and reliability. The proposed model enables high-fidelity prediction of solute transport processes using only fracture network geometric parameters and hydrodynamic conditions. This provides critical support for low-cost, efficient predictions of solute transport in fractured rocks. The findings have significant theoretical implications for rapid assessments of subsurface pollution and efficient underground resource exploitation. Additionally, the revealed quantitative control mechanisms of fracture network geometry on solute transport establish a theoretical basis for studying the coupling between rock mass structural evolution and hydrochemical signals. These insights hold potential applications in tracing rock failure states and early warning of geohazards using hydrochemical signals.