Experimental study on mechanical properties of loess-like saline soil in seasonal frozen regions under wetting-drying cycles

To examine the impacts of wetting-drying and freeze-thaw cycles on the mechanical properties and microstructure of loess-like saline soil in seasonally frozen regions, unconfined undrained triaxial shear tests (UU) and scanning electron microscopy (SEM) are employed. The study analyzes the variations in stress-strain curves and shear strength parameters of saline-alkaline loess under different cycles of wetting-drying and freeze-thaw, as well as their microstructural characteristics. The results indicate that the stress-strain curves of the samples subjected to various drying-wetting and freeze-thaw cycles exhibited a strain-softening behavior. Under wetting-drying and wetting-drying-freeze-thaw conditions, as the number of cycles increase, the cohesion first increases, then decreases, and eventually stabilizes, with the lowest cohesion observed at six cycles. In contrast, under freeze-thaw conditions, cohesion gradually decreases with increasing number of cycles. The variation in the internal friction angle is relatively small across different cycling conditions. After multiple cycles, the volume of single-grain structures within the soil decreases, and the proportion of bridged structures increases, leading to a loosening of the soil structure and a reduction in strength.