In clod regions, frost action can significantly impact roadway performance due to frost heave and thaw settlement of the subgrade soils. The severity of the damage depends on the soil properties, temperature, freeze-thaw cycles, and water availability. While nominal expansion occurs with the phase change from pore water to ice, heaving is derived primarily from a continuous water flow from the vadose zone to growing ice lenses. The temperature gradient within the soil influences water migration towards the freezing front during winter, where ice nucleates, coalesces into lenses, and grows. When the temperature increases during the spring season, the ice melts, inducing thaw settlement and causing a reduction in soil strength. This study investigated the effect of soil properties, including the gradation and soil thermal properties (thermal conductivity, specific heat, thermal diffusivity), on the frost susceptibility of soils from Iowa and North Carolina through the laboratory frost heave and thaw settlement test. Total heave, heave rate, temperature profile, frost penetration depth, and frost penetration rate were measured as a function of time. The results showed that soils that had higher silt content had higher heaving. Maximum frost penetration rate was observed for soils with higher thermal diffusivity. Moreover, the impact of climatic conditions on frost heave was assessed by conducting tests under varying conditions of water availability (open vs. closed system), multiple freeze-thaw cycles, and temperature gradients. It was observed that the presence of an external water source significantly increased the magnitude of heave, resulting in a seven times higher total heave compared to those soils in a closed system. The soil specimens experienced a continuous increase in heave until the sixth freeze-thaw cycle, after which it stabilized. The freezing process caused the soil specimens to exhibit a high rate of water intake, which decreased during thawing. Under extended freezing periods, both soils showed the maximum total heave when subjected to a lower temperature gradient. The silty sand/silty clay soil experienced more significant frost heave and water intake volume compared to low plasticity clay, owing to its high hydraulic conductivity.
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