# Effects of Cyclical Climate Change on Water Temperature Characteristics of Permafrost Slopes
###### Abstract  
Under the action of freeze-thaw cycles, the internal temperature and water distribution of slope soils in cold regions change significantly, which directly affects the stability of slopes. In order to study the differences in hydrothermal reactions at different depths and their impacts on the stability of slopes. This study establishes both a freeze-thaw model and a hydrothermal coupling model, combining field measurements with numerical simulations to examine the dynamic changes in hydrothermal characteristics within the slope. The results indicate that the variation in slope temperature with depth can be divided into three stages: initial freezing, stable freezing, and thawing. In the freezing stage, the negative temperature gradient drives water to migrate towards the freezing front, forming segregated ice and inducing frost heave. In the thawing stage, the latent heat released by the phase change in segregated ice promotes water to move towards the slope toe, increasing the water content there and indirectly exacerbating the risk of slope instability. The heat and moisture transfer in frozen soil slopes shows non-linear and dynamic characteristics. The unique process of one-way freezing and two-way thawing makes the thawing rate 1.35 times that of the freezing rate, and this asymmetric characteristic is the key to understanding the mechanism of slope instability. permafrost; hydrothermal coupling; plateau slopes; freeze-thaw changes 2025  
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been found that there is a specific response relationship between soil moisture content and temperature during the freeze-thaw process [12]. Following freeze-thaw cycles, the soil's thermal conductivity decreases [14], and the factor of safety for slopes gradually diminishes with each successive freeze-thaw cycle [15]. In practical applications, certain data required for projects cannot be obtained through experiments, and the limited experimental results hinder a comprehensive understanding of the underlying physical mechanisms. Consequently, the development of mathematical models facilitates a more thorough understanding of these mechanisms and enables reasonable predictions and recommendations for engineering applications. The model proposed by [PERSON] et al. [16] effectively predicts the changes in thermal state and moisture content as the number of freeze-thaw cycles increases. [PERSON] et al. [17] developed a hydrothermal-mechanical coupling model and computational methods to investigate and validate the spatial-temporal distribution of temperature, water, and mechanical fields under long-term freeze-thaw cycles. Furthermore, numerous studies [18; 19; 20] have utilized the PDE module for hydrothermal simulations or fluid-solid coupling, with results indicating minimal simulation errors and that the trends of simulated values for total soil moisture content and temperature closely match those of the measured data [21]. [PERSON] and [PERSON] [22] established a hydrothermal coupling model for frozen soil, revealing that the stepwise temperature variation over time reflects the water phase transition in the soil during the freezing process. In addition, [PERSON] et al. [23] found that under hydrothermal coupling, the temperature gradient and cover pressure significantly influence the pore water pressure gradient, and that soil moisture content changes typically lag behind temperature variations. [PERSON] et al. [24] observed that during unidirectional freezing, the freezing front in the soil column initially moves downward rapidly, with the freezing range gradually expanding over time. The rate of movement of the freezing front then decreases and stabilizes. Previous studies have explored the impacts of the freeze-thaw process of frozen soil on the mechanical properties and stability of soil, and have also taken note of the hazards of the freeze-thaw process in slope areas.