Strength Characteristics of Sand–Silt Mixtures Subjected to Cyclic Freezing-Thawing-Repetitive Loading

Daily freezing-thawing-repetitive loading is a critical factor affecting soil stability. This study assesses the strength of sand–silt mixtures with various silt fractions (SFs) subjected to cyclic freezing-thawing-repetitive loading. Specimens with SF of 0–100% were prepared with a fixed relative density of 60%. The number of repetitive loadings (N) was 1, 100, and 1000 for each specimen with different SFs. After three cycles of freezing-thawing-repetitive loading, the specimens were frozen at −5 °C for the uniaxial compression test. Test results show that the change in relative density (∆D(r)) increases with the increase in SF up to 30% and decreases as SF increases beyond 30% owing to the change in the void ratio. The volumetric unfrozen water content (θ(u)) increases with the increase in both SF and N owing to the effect of the physicochemical characteristics of soils on small voids. Unconfined compressive strength of sand-dominant mixtures (SF ≤ 30%) is reinforced by ∆D(r). By contrast, for silt-dominant mixtures (SF > 30%), the unconfined compressive strength decreases with the increase in θ(u) and N due to lubricant role and sands dispersion. Thus, the effects of SF and N should be considered for sand–silt mixtures that have a probability to undergo cyclic freezing-thawing-repetitive loading.