Volumetric behavior of an unsaturated clayey soil-rock mixture subjected to freeze-thaw cycles: A new insight

The volumetric behavior of clayey soil-rock mixtures under freeze-thaw action is very important for the design of anti-frost heave in cold-region engineering. However, existing studies mainly focus on the effect of freeze-thaw cycles on the global volume change of fine-grained soils, and few attempts have focused on mixed soils with coarse particles such as clayey soil-rock mixtures. In this study, a series of laboratory freezing-thawing tests were conducted to investigate the effects of the freeze-thaw cycles and rock content on the global volume change, diameter change, and height change behaviors of cylindrical soil-rock mixture samples. The results demonstrate that: 1) the volumetric behavior of the samples under freeze-thaw cycles is closely related to the rock content, which is mainly because different rock contents dominate the different skeleton structures. 2) For samples with 0%, 10%, and 30% rock content, the global volume of compacted samples shows shrinkage upon freezing and expansion after thawing. However, the global volume of the sample with 50% rock content began to shrink after three freeze-thaw cycles. 3) Compared with the samples not subjected to freeze-thaw weathering, the height of samples with 0%, 10%, and 30% rock content shows shrinkage upon freezing and expansion after thawing no matter what the number of freeze-thaw cycles is. However, the diameter and height of the sample are always shrinking, regardless of whether they are frozen or thawed. 4) Upon freezing, the shrinkage of the sample's global volume and diameter tends to decrease linearly with the increase of rock content, but the shrinkage of the sample's height is not sensitive to the change of rock content. Upon thawing, the global volume and height of the sample exhibit a trend from expansion to contraction with increasing rock content, but the shrinkage of the diameter of the sample is nearly the same no matter what the rock content is. Furthermore, a computed tomography (CT)-based mesoscopic structural characteristic and two idealized schematic diagrams well illustrated the evolution mechanism of the volumetric behavior of an unsaturated clayey soil-rock mixture subjected to freeze-thaw cycles.