Coupled thermo-hydro-mechanical model for porous materials under frost action: theory and implementation

This paper introduces the development and implementation of a multiphysical model to simulate the coupled hydro-thermo-mechanical processes in freezing unsaturated porous materials. The model couples the Fourier's law for heat transfer, the generalized Richards' equation for fluid transfer in unsaturated media, and the mechanical constitutive relationship. Coupling parameters were defined to transfer information between field variables. Relationships, such as the similarity between drying and freezing processes and the Clapeyron equation for thermodynamic equilibrium during phase transition, were utilized to describe the effects of frost action. The coupled nonlinear partial differential equation system was solved under typical boundary conditions. The simulation results indicate that the model properly captured the coupling characteristics such as the thermally induced hydraulic and mechanical change in porous materials. Simulation was also conducted on an instrumented pavement section. The results of multiphysical simulations match reasonably well with the field-monitoring data.