Effect of freeze–thaw cycle on hydraulic conductivity of compacted clayey soil

When filling embankment dams in cold regions, engineers must solve two freeze–thaw cycle (FTC)-induced soil problems. First, compacted soil constituting the dam is subjected to the FTC during dam construction. Second, loose soil material (LSM), which is subjected to the FTC, fills the dam. To investigate the effects of the aforementioned two problems on the hydraulic conductivity of compacted clayey soil, a series of permeation tests on clayey soil compacted before and after FTC were conducted in this study. The results showed that for the first problem, the hydraulic conductivity of compacted clayey soil subjected to one FTC significantly increases by two to three orders of magnitude because FTC-induced cracks can cause preferential flow in the permeation process. For the second problem, when the FTC number is less than a critical number, the FTC of the LSM may result in the development of united soil particles, thereby increasing the effective porosity ratio and hydraulic conductivity of the compacted soil. It was discovered that the hydraulic conductivity of compacted soil can increase by one to three times when the LSM is subjected to 10 FTCs. When the FTC number exceeds a critical number, the effective porosity ratio and hydraulic conductivity of the compacted soil may decrease with the FTC of the LSM. This should be investigated in future studies, and the results can be used to improve engineering management processes when filling embankment dams during winter in cold regions.