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

Abstract

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 (∆Dr) 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 (θu) 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 ∆Dr. By contrast, for silt-dominant mixtures (SF > 30%), the unconfined compressive strength decreases with the increase in θu 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.

Assessing the State of Structural Foundations in Permafrost Regions by Means of Acoustic Testing

“…Currently, there are no direct monitoring methods for this parameter. F a = f (A t ) is found, where A t is the soil thawing coefficient that is based on the freezing temperature of soils, which is not constant [14][15][16].…”

“…Before acoustic testing, the samples were also kept at room temperature for the same periods. Based on the results of the tests, the velocity of propagation of the longitudinal wave (16) and the value of shear strength in the soil along the adfreeze zone (17) were calculated.…”

“…The activation of freeze-thaw processes greatly aggravate this problem [14,15]. It is also important to note the influence of the freeze-thaw cycle affecting the physical and mechanical properties of soils [16]. Temperature control methods are often used as part of integrated condition monitoring systems [17,18].…”