A coupled phase‐field method (PFM) and thermo‐hydro‐mechanics (THM) based framework for analyzing saturated ice‐rich porous materials

Abstract This study proposes a novel framework for ice‐rich saturated porous media using the phase‐field method (PFM) coupled with a thermo‐hydro‐mechanical (THM) formulation. By incorporating the PFM and THM approaches based on the continuum theory, we focus on the mechanical responses of fully saturated porous media under freeze‐thaw conditions. The phase transition between liquid water and crystalline ice can be explicitly expressed as captured by evaluating the internal energy and implementing thermal, mechanical, and hydraulic couplings at a diffused interface using PFM. Accurately modeling the coupled mechanical behaviors of ice and soil presents significant challenges. Therefore, in previous numerical frameworks, ad hoc constitutive models were adopted to phenomenologically estimate the overall behavior of frozen soil. To address this, we employ a method that differentiates between the kinematics of the solid and ice constituents, enabling our framework to accommodate distinct constitutive models for each constituent. Within this framework, we naturally introduce anisotropy of frozen soil as it undergoes the freezing process by integrating a transversely isotropic plastic constitutive model for ice. We illustrate the capabilities of our proposed approach through numerical examples, demonstrating its effectiveness in modeling the phase transition process and revealing the overall anisotropic responses of frozen soil.