A fully coupled thermo-poro-mechanical finite element analysis to predict the thermal pressurization and thermally induced pore fluid flow in soil media

Abstract

Temperature gradient and heat transfer in saturated porous media may affect pore fluid pressure and/or pore fluid flow depending on thermal, mechanical, and hydraulic properties of the media and the saturating fluid. Therefore, several Thermo-hydro-mechanical (THM) models have been developed to theoretically analyze the thermal behavior of soil media. In this study a coupled thermo-poro-mechanical model is adopted to investigate the heat and mass transfer in deformable porous media in a transient and quasi-steady state conditions. The Effects and importance of different properties of porous media are carefully taken into account to simulate two different cases with different scenarios. The results confirm that in order to accurately predict the thermal pressurization and changes in total stress, temperature dependency of properties of the soil and saturating fluid must be considered carefully. It is found that even a slight perturbation in porosity variation and temperature dependency of the thermal expansion coefficient of the fluid can greatly influence the thermal pressurization of pore fluid in very low permeable soils (e.g. clays), while variations of pore fluid density governs thermally-induced pore fluid flow in high permeable soils (e.g. sands and silty sands). Moreover, the feasibility of heat convection and heat-induced pore fluid flow is discussed in a parametric study with different temperature and permeability values. The results demonstrate that the Boussinesq approximation is a key assumption when dealing with heat-induced pore fluid flow in quasi-steady state condition.