Available online at www.sciencedirect.com ScienceDirect Comput. Methods Appl. Mech. Engrg. 372 (2020) 113358 www.elsevier.com/locate/cma A unified water/ice kinematics approach for phase-field thermo-hydro-mechanical modeling of frost action in porous media Abdel Hassan Sweidan, Yousef Heider ∗ , Bernd Markert Institute of General Mechanics, RWTH Aachen University, Eilfschornsteinstr. 18, 52062 Aachen, Germany Received 8 April 2020; received in revised form 3 August 2020; accepted 3 August 2020 Available online xxxx Abstract This research work introduces a novel phase-field thermo-hydro-mechanical (P-THM) modeling approach that allows to deeply understand and model the freezing–thawing cyclic process in a fluid-saturated porous medium. In this, a biphasic macroscopic, non-isothermal porous media model, augmented by the phase-field method (PFM), is applied to account for the temperature development, the interstitial pore-fluid flow, and the volumetric deformations due to ice formation (phase change). Utilizing the theory of porous media (TPM) in the continuum mechanical formulation provides a well-founded basis for the description of deformable, fluid-saturated, non-isothermal porous solid materials. Of particular importance in the underlying work is the unified kinematics treatment of the ice and water constituents as a single pore-fluid, where the PFM is employed for the description of the phase transition between both constituents. The PFM is a diffuse-interface approach that relies on the specification of the free energy density function as the main driving force in the phase transition. It employs a scalar-valued, phase-field variable to indicate the state of the pore-fluid, i.e., a solid (ice) or a liquid (water). A significant virtue of using the PFM approach is its viability in the implementation within standard finite element frameworks, as no need to explicitly track the moving boundaries (interfaces) of the phase-change constituent. The numerical examples and comparisons presented at the end of the manuscript demonstrate the ability, reliability and usefulness of the proposed modeling framework in describing the freezing–thawing process in a saturated porous solid under thermal loading within an elastic deformation limit. c ⃝ 2020 Elsevier B.V. All rights reserved. Keywords: Phase-field modeling; Phase-change materials; Freezing in porous media; Unified water–ice kinematics; Thermo-hydro-mechanical coupling 1. Introduction In cold regions where periodic freezing occurs, saturated and unsaturated soils underneath pavement or concrete foundations may experience frost damage due to freeze–thaw cycles. Moreover, employing artificial ground freezing (AGF) in soft soils for providing temporary ground support during tunnel excavation or controlling the groundwater during geotechnical construction might lead to heave-induced or settlement-induced damages [1]. The freezing process in porous media is characterized by a coupled heat and mass transport and is accompanied by ice expansion (9% volume dilation referred to the volume of liquid) and considerable deformation in the saturated porous ∗ Corresponding author. E-mail address: heider@iam.rwth-aachen.de (Y. Heider). https://doi.org/10.1016/j.cma.2020.113358 0045-7825/ c ⃝ 2020 Elsevier B.V. All rights reserved.