A fully coupled thermo-hydro-mechanical model for simulating multiphase flow, deformation and heat transfer in buffer material and rock masses

This paper presents a numerical method for modeling coupled thermo-hydro-mechanical processes of geomaterials with multiphase fluid flow. A FEM code has been developed and validated for modeling the behavior of porous geological media, and is equally applicable for modeling coupled THM processes in rocks. The governing equations are based on the theory of mixtures applied to the multiphysics of porous media, considering solid phase deformation, multiphase fluid flow, and heat transport. New numerical techniques have been developed for more efficient FEM formulation and equation solution for modeling saturated or partially saturated water flow, gas flow and heat transfer in deformable porous media, as are commonly encountered in performance and safety assessment of underground radioactive repositories. The code has been validated against an experimental benchmark test, which involves bentonite under laboratory conditions, with good results. Several critical outstanding issues for modeling coupled processes of geomaterials are discussed in depth.