Theoretical analysis and numerical simulation of hydrothermal coupled process in unsaturated soils

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The vapor in unsaturated soil migrates and condenses due to the temperature gradient, which leads to the change in local water content and further causes engineering problems such as road mud squeezing and frost heave in cold regions. Consequently, the coupled process of water-vapor and heat transfer in soils is one of the major concerns in the study of soil behaviors. This paper establishes the governing equations of water-vapor and heat migration respectively, based on the theoretical framework of mass and energy conservation. Subsequently, a one-dimensional finite element model (FEM) is developed to simulate the hydrothermal coupled process in unsaturated soils such as sand, loam, and clay. The simulation results indicate that water and vapor migrate from the cold end to the warm end under the temperature gradient. The vapor migration is most dominant in sand, followed by loam, and weakest in clay. However, due to the poor water holding capacity, water in sand is significantly affected by gravity, causing the increase of surface water content not noticeable. The simulation results under different initial water content reveal that the vapor migration cannot be ignored when the initial water content is extremely low, and the water migration under the temperature gradient needs to be adequately considered.

9th International Congress on Environmental Geotechnics (ICEG2023)

Coupled Processes in Environmental Geotechnics