A thermo-hydro-mechanical finite-element model with freezing processes in saturated soils

Freezing and thawing of soil are dynamic thermo-hydro-mechanical (THM) interacting coupled processes,and have attracted more and more attention due to their potentially severe consequences in geotechnical engineering. In this article, a fully-coupled thermo-hydro-mechanical freezing (THM-F) model is established for advanced system design andscenario analysis. The model is derived in the framework of the Theory of Porous Media (TPM), and solved numerically with the finite element method. Particularly, the derivation of theoretical aspects pertaining to the governing equations, especially including the thermo-mechanical decomposition treatment of the solid phase is presented in detail. Verification examples are provided from purely freezing (T-F),THM, and THM-F perspectives. Attention is paid to the heat and mass transfer, thermodynamic relations and the formation of frost heave. The migration of pore fluid from the unfrozen zone to the freezing area, and the blockage of pore space by ice lenses within the porous media are studied. The model is able to capture various coupled physical phenomena during freezing, e.g. the latent heat effect, groundwater flow alterations, as well as mechanical deformation.