Thermo-hydro-mechanical coupling analysis model for unsaturated soils with high degree of saturation and its verification

Unsaturated soils with high saturation (USHS) are widely distributed around the coastal areas and rivers / lakes in China, whose internal free bubbles are sensitive to temperature and pressure, causing complex thermo-hydro-mechanical (THM) coupling responses and subsequent changes of soil compression and seepage characteristics. Based on the FEM platform OpenGeoSys, the governing equations for saturated soils are expanded to be applied for USHS by introducing the gas mass equation. The Clapeyron, Kelvin-Laplace and other equations are embedded, and a THM coupling model for USHS is established, thus enriching the processes and functions of OpenGeoSys. Verification cases are carried out by comparing with the experimental and numerical results, and then the coupling behaviors of USHS are further explored. It is revealed that the consolidation process of soils can be significantly affected by closed bubbles. When temperature and pressure change, the pressure dissipation dominates initially, whereas accumulates and reaches the peak with heat transfer and enhancement. The gas diffusion can be accelerated by temperature rise, meaning greater pressure dissipation rate accompanied by higher temperature.