EXPERIMENTAL STUDY ON MECHANICAL PROPERTIES AND SOIL-WATER CHARACTERISTIC CURVE OF SALINIZED LOESS UNDER WET-DRY AND FREEZE-THAW CYCLES

Through multi-cycle environmental simulation tests(0-8 drying-wetting cycles and 0-50 freeze-thaw cycles), this study investigated the coupled effects of drying-wetting and freeze-thaw cycles on salinized loess. Triaxial shear tests, filter paper method measurements, scanning electron microscopy(SEM), and PCAS-based quantitative microstructural analysis were employed to elucidate the mechanisms by which cyclic environmental conditions influence mechanical strength and water-retention behavior. The results indicate that: (1)Mechanical strength exhibits a three-stage evolution: initial enhancement due to salt crystallization filling the soil skeleton; subsequent rapid degradation caused by water-salt phase changes damaging the structural framework; and eventual stabilization after reaching critical cycle thresholds, where the soil develops a more compact structure. (2)As the number of cycles increases, the soil-water characteristic curve(SWCC)shifts toward lower suction and lower water content. Van Genuchten model fitting indicates reductions in both saturated and residual water content, reflecting a deterioration in water-retention capacity. (3)Microscopic analyses reveal that coupled cycles transform interparticle contacts from surface-to-surface to point-to-surface types, promote crack development, and lead to structural loosening. These microstructural changes result in the coupled degradation of mechanical and hydraulic properties.