Experimental study and generalized predictive model of thermal conductivity of saline soil

Soil salinization is a critical factor contributing to land degradation, with substantial impacts on the thermal and physical behavior of soils. In order to study the changes in thermal conductivity of saline soils, the thermal conductivity of soil samples with different water contents (16%, 18%, 20%) and salt contents (0%, 0.5%, 1%) at different temperatures was measured, and a generalized predictive model for the thermal conductivity of saline soil was proposed. The results reveal a three-phase response of thermal conductivity to temperature variation: an initial slight decrease, followed by a sharp increase, and finally a decrease towards stability. Thermal conductivity increases with rising water content. When freezing begins, the thermal conductivity increases, but decreases with the formation of microfissures due to frost heave. The relationship between thermal conductivity and salt content is related to water content. In soils with low water contents (16% and 18%), salinity first raises thermal conductivity. Beyond a certain increase, salinity compresses the soil-colloid electric double layer (EDL), induces flocculation, and lowers thermal conductivity. High salt content (> 1%) compress the EDL of soil colloids, promoting flocculation and reducing thermal conductivity. Based on experimental results, a generalized predictive model for the thermal conductivity of saline soil was proposed, which comprehensively considers the effects of water content, salt content, and frost heave. The model validation showed strong consistency (R² range of 0.635–0.921). These findings contribute to a better understanding of heat transport in saline soils and offer practical insights for engineering applications in cold and salinized regions.