Advances in physical interaction mechanism between highly compacted bentonite and pore solution

The swelling performance of highly compacted bentonite deteriorates due to infiltrating rock groundwater and chemical components during its long-term operation, ultimately posing a threat to disposal safety. This paper reviews recent research on the physical interaction between compacted bentonite and pore solution, based on phenomena related to pore solution's impact on buffering properties. The results show that the physical mechanism of pore solution on highly compacted bentonite includes crystal layer swelling, diffusion double layer swelling and adsorption effects. The effect of pore solution on crystal layer expansion is related to its concentration. The effect of pore solution on crystal layer swelling is promoting at low concentration and inhibiting at high concentration, which depends on the difference between pore solution suction and critical suction. The inhibition of pore solution on double layer expansion is the main factor behind enlarged pore channels, higher permeability, and diffusion coefficients. pH changes and nuclide hydrolysis alter adsorption characteristics, while competitive background ion adsorption reduces bentonite's nuclide capacity. Current shortcomings include parameter generalization for pore solution effects, effective porosity quantification, and adsorption models. Therefore, the further optimization of chemical parameters of pore solution in the constitutive model, clarification of the equivalent quantification of pores at different scales, and construction of a multi-component competitive adsorption model under the constraint of compacting bentonite are still the key directions for further research in the future.