Purpose <p>Landfill barrier systems serve as a critical barrier in pollution control, with their performance directly impacting ecological safety. However, the continuous leaching of salt ions from landfill leachate can lead to salt accumulation within the barrier, compromising its impermeability over time. This study investigates the evolution of the hydraulic performance of sand-bentonite barrier materials under exposure to low- and moderate-concentration salt solutions.</p> Methods <p>A series of centrifuge test for soil water behaviors and direct shear tests for soil strength were performed on sand-bentonite mixtures with different initial dry densities under salt solution exposure to systematically study their water retention and shear strength evolution in low- to moderate-salinity conditions. Additionally, scanning electron microscopy (SEM) was used to analyze microstructural changes and salt ion interaction mechanisms.</p> Results <p>The results demonstrate that salt solution exposure significantly influences the soil’s hydro-mechanical properties. Water retention capacity exhibits a continuous decline with increasing salinity. In contrast, shear strength initially decreases under low-salinity conditions but subsequently increases at higher concentrations, which is attributed to salt-induced fabric alteration. Microstructural analysis reveals progressive degradation of bentonite’s flaky structure under saline conditions, resulting in diminished swelling capacity and compromised barrier performance.</p> Conclusion <p>Salt solution erosion significantly affects the water retention and mechanical properties of sand-bentonite mixtures.</p>