Application of a Thermo-hydro-mechanical Model for Freezing and Thawing

Recently, a constitutive model has been developed to describe the mechanical behaviour of frozen soil as a function of temperature, all the way to the unfrozen state, and vice versa [1]. The model has been implemented as a user-defined soil model (UDSM) in the geotechnical finite element code PLAXIS 2D and applied in practical thermo-hydro-mechanical boundary value problems. One of the problems with the use of a model for frozen / unfrozen soil is that it involves several parameters of which quite a few are not very common to geotechnical engineers. Hence, one of the goals of this study is to provide more information on the meaning and the determination of the model parameters. As an example of the use of the constitutive model and its implementation, one application is presented: it is a chilled pipeline causing a drop in the ground temperature leading to frost heave. Its results show that the model can simulate frost heave in a qualitative manner, and that the robustness of the numerical implementation is still sensitive to the choice of boundary conditions, temperature gradients, and time.