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 paper, a fully coupled thermo-hydro-mechanical freezing (THM-F) model is established for advanced system design and scenario analysis. The model is derived within the framework of the theory of porous media and solved numerically using the finite-element method. Particularly, the derivation of theoretical aspects pertaining to the governing equations, including in particular the thermo-mechanical decomposition treatment of the solid phase, is presented in detail. Verification examples are provided from purely freezing, 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 – for example, the latent heat effect, groundwater flow alterations and mechanical deformation.