Research Progress on Coupled Solute Transport Theory in Bentonite-Based Engineering Barriers

Abstract:

This paper provides a detailed review of research on isothermal coupled solute transport （ICST） theory and， and compares solute flux predictions from different theoretical models using COMSOL numerical software. The results show that ICST models include both the counter-diffusion （CD） model and the salt-diffusion （SD） model. Although the flux predictions of the CD and SD models are basically consistent， the SD model is theoretically more accurate. The advection-diffusion （AD） model overestimates solute transport. However， when the restricted diffusion is considered， the flux predictions obtained by the AD model substantially diminish the discrepancies observed with the ICST models. In practical applications， it is recommended to appropriately use the SD model or ADC model considering site-specific conditions. Given the complexity of the near-field environments in engineering barriers， future theoretical research should focus on elucidating coupled solute transport mechanisms under non-isothermal， unsaturated， and soil deformation conditions， and on developing a fully coupled thermo-hydro-mechanical-chemical solute transport model that accurately reflects the effects of concentration and temperature on model parameters.