Effect of Freeze–Thaw Cycles on Consolidation Behavior of Two Plastic Fine Soils

In cold areas, freeze–thaw cycles are important in the design of engineering projects since they affect mechanical properties of fine-grained soils. In freeze–thaw cycles (FTCs), soil engineering properties change as water transforms into ice under thermodynamic conditions below 0 °C. In this research, the effect of FTCs on consolidation parameters of two fine-grained soil types with two different values of plasticity index has been studied. Nine FTCs in a closed system and oedometer test were applied to samples, considering loading and unloading phases. Based on experimental results, the permeability coefficients of both soil types increased significantly when the number of FTCs increased to three cycles. Due to FTCs, the permeability, compressibility, and swelling indexes increased up to 26, 2.6, and 1.5 times of initial values, respectively. After the third cycle, the increase in the permeability coefficient and compressibility index decreased significantly. In addition, the swelling index, consolidation loops area, and swelling potential increased by the sixth cycle, after which, these changes were almost zero. The results of this study also showed that the soil with more plasticity index is more susceptible to FTCs.