Impact of Freeze-Thaw Cycles on Soil Properties and Engineering Problems in Cold Regions

The changes in moisture, temperature, and displacement during freeze-thaw cycles are critical factors influencing frost heave and thaw settlement in cold regions. As the number of freeze-thaw cycles increases, the soil's internal structure undergoes continuous changes, leading to various engineering problems such as roadbed cracking, pipeline deformation, and slope instability [5-7].

In cold regions, the soil experiences significant fluctuations in unfrozen water content, heat flow, temperature, volume, and dry density due to the cyclical freezing and thawing during seasonal changes. These variations interactively affect the soil's strength and deformation characteristics [8-10].

Numerous studies have investigated the water and heat migration and frost heave characteristics of silty clay under freeze-thaw conditions. It is observed that soils with higher initial water content freeze earlier than those with lower initial water content, displaying greater sensitivity to sudden temperature changes [1]. Zhang et al. proposed a calculation method to evaluate the frost heave of original and migrating water based on unidirectional freezing tests [2]. Tian et al. introduced a novel method using nuclear magnetic resonance technology to determine unfrozen water content in frozen soil during water migration [3].

Research indicates that multiple ice lenses form in the soil when the thermal diffusivity coefficient surpasses the hydraulic conductivity coefficient during temperature fluctuations [11]. Driven by temperature gradients, water migrates within the soil, influencing moisture redistribution [14]. Liu et al. developed a TH coupling model to enhance the prediction of the freezing process in porous media [12].

The deformation of frozen soil during freeze-thaw cycles is primarily attributed to consolidation in the unfrozen zone and frost heave in the frozen zone [4]. Repeated freeze-thaw cycles cause soil samples to transition from an unstable state to a new dynamic equilibrium. This results in decreased dry density for samples with initially high dry density and increased dry density for samples with initially low dry density after the freeze-thaw cycles [13].