Degradation Mechanisms of Saline Clay Mechanical Properties under Coupled Wet–Dry–Freeze–Thaw Cycling

A water conveyance open channel project in the northern Xinjiang region is affected by changing climate and interruptions in water supply, leading to significant deterioration in the mechanical properties of saline clay and frequent sliding failures of the canal slope. To delve deeper into its failure mechanism, direct shear, compression, and scanning electron microscopy tests were conducted on saline clay subjected to wet–dry–freeze–thaw (WDFT) cycles to examine the impacts of WDFT cycles and salinity on its mechanical properties, thereby revealing the physical mechanism behind the degradation of its mechanical properties. The findings indicate the following: (1) With more WDFT cycles, cohesion declines (ice disrupts particle bonds) while friction angle stays stable. Higher salinity reduces both by increasing salt crystallization pressure and lubrication. (2) Cyclic stress raises compressibility exponentially but lowers yield stress. Salinity linearly increases compressibility yet stabilizes the structure slightly. Compression/rebound indices show minimal sensitivity to cycles or salinity. (3) Big data modeling identifies cycles, salinity, and three-dimensional porosity (V3D) as key strength influencers. The multifactor model outperforms single-factor versions and aligns with literature data. These findings aid in saline clay stability analysis.