Experimental Study on Clay Erodibility Subjected to Freeze–Thaw and Varying Temperature Conditions through Hole Erosion Tests

The erosion of cohesive soils poses a significant threat to the stability of earth structures such as roadbeds and earth-filled dams, especially in cold regions. Presently, research on the erodibility of clay mainly focuses on its variation under regular testing conditions, while the environmental factors encountered in high-latitude areas are generally ignored. In seasonally frozen regions, clayey soils are subjected to various environmental forces such as the low ambient temperature, freeze–thaw cycles, and addition of deicing salts, which have strong effects on clay’s erosion characteristics. In this study, an enhanced water-recyclable hole erosion test (HET) apparatus, including a consolidation sample preparation device and a temperature control unit, is used to quantify clay’s erodibility. A total of 13 soil samples are prepared and tested with the enhanced HET facility under different conditions of temperature, numbers of freeze–thaw cycles, and deicing salt concentrations. The results show that the soil critical shear stress decreases from 255 to 168 Pa with the temperature increases from 3°C to 8°C. The freeze–thaw treatment reduces the erosion resistance of the soil, particularly after the first freeze–thaw cycle, resulting in a 20.6% reduction in the critical shear stress. The addition of NaCl and CaCl2 (inorganic deicing salts) enhances soil erosion resistance, while the addition of CH3COOK (organic deicing salt) weakens soil erosion resistance. Multiscale testing techniques, including the scanning electron microscope, mercury intrusion test, and gas adsorption test, reveal that the varying erodibility is related to the micropores between clay aggregates, clay mineral–electrolyte interactions and evolution of internal aggregate structures.