STUDY ON THERMO-HYDRAULIC COUPLED MIGRATION IN UNSATURATED CLAY

The heat exchange efficiency of energy piles is influenced by the thermal conductivity of the clay, which in turn is affected by the saturation degree. The variation in saturation degree is closely related to the thermal-hydro coupled migration in the clay. This correlation, especially in unsaturated cohesive clay foundations, is crucial for the long-term stability of energy piles. Therefore, this study aims to investigate the impacts of temperature rise and fall, of initial moisture content, and of dry density on the thermal-hydro coupled migration behavior in unsaturated clay using a self-designed apparatus that mimics the operational conditions of energy piles. The experimental results indicate that: under the same temperature gradient, the initial moisture content of the clay has influences on both temperature and moisture migration, resulting in higher initial moisture content and leading to smaller moisture migration and greater temperature variation. When the initial moisture content is constant, there is a positive correlation between the peak value of moisture content variation and temperature gradient caused by moisture migration. Specifically, with a temperature increase of 1 ℃, the peak value of moisture content increases by 0.044%. During both heating and cooling processes, there are significant differences in clay moisture migration, while the distribution of temperature change remains consistent. Dry density has a minor impact on temperature distribution but significantly affects moisture content distribution. The soil-thermal-hydro-air multi field coupling calculation based on the elastoplastic constitutive model of unsaturated soil can quantitatively describe the thermal-hydro coupled migration in unsaturated clay.