This paper introduces a thermo-hydro-mechanical (THM) framework to model thaw consolidation in permafrost regions. By integrating internal energy degradation functions and a modified Cam-Clay model within a phase-field damage framework, the model focuses on simulating the simultaneous effects of phase change and particle rearrangement. The model integrates two distinct phase-field variables with the modified Cam-Clay plasticity framework. One phase-field variable monitors pore phase composition, while the other captures particle rearrangement. These variables are directly coupled to the constitutive model, providing critical data for updating the stress-strain relationship by accounting for particle rearrangement-induced softening and hardening effects due to volumetric deformation. The model converges to the modified Cam-Clay model when there is no phase change. This approach addresses a significant gap in existing models by capturing the associated microstructural evolution and plastic softening in thaw-sensitive soils. Validation efforts focus on experimental scenarios assessing both the mechanical impacts of thaw consolidation and the dynamics of phase transitions, particularly emphasizing latent heat effects. The results demonstrate the proposing model's capability of handling complex behaviors of permafrost under thaw conditions, confirming its potential for enhancing infrastructure resilience in cold regions.

The complex multiphase composition of frozen soil induces significant coupling interactions between the thermal, hydrological, mechanical, and damage fields during deformation, particularly under dynamic loading conditions. This study presents a hybrid decomposition phase-field model to investigate the multi-field coupling behavior and damage mechanisms of frozen soil. Unlike the spectral decomposition model, the proposed framework integrates isotropic degradation and the spectral decomposition methods, thereby enabling the simulation of damage evolution under compressive-dominated loading conditions. The model incorporates the viscous effects and strain rate sensitivity to accurately capture the dynamic response of frozen soil and establishes governing equations for coupled displacement, temperature, and fluid pressure fields. The applicability of the model was validated through confined compression experiments on frozen soil, demonstrating its capability to predict distinctive damage features, such as compaction bands oriented perpendicular to the loading direction, which represent the competitive interaction between the softening mechanism of pore collapse and the hardening mechanism of microstructural densification. This study provides significant advancements in the theoretical understanding and numerical simulation of the dynamic mechanical behavior of frozen soil.

This work is devoted to numerical analysis of thermo-hydromechanical problem and cracking process in saturated porous media in the context of deep geological disposal of radioactive waste. The fundamental background of thermo-poro-elastoplasticity theory is first summarized. The emphasis is put on the effect of pore fluid pressure on plastic deformation. A micromechanics-based elastoplastic model is then presented for a class of clayey rocks considered as host rock. Based on linear and nonlinear homogenization techniques, the proposed model is able to systematically account for the influences of porosity and mineral composition on macroscopic elastic properties and plastic yield strength. The initial anisotropy and time-dependent deformation are also taken into account. The induced cracking process is described by using a non-local damage model. A specific hybrid formulation is proposed, able to conveniently capture tensile, shear and mixed cracks. In particular, the influences of pore pressure and confining stress on the shear cracking mechanism are taken into account. The proposed model is applied to investigating thermo-hydromechanical responses and induced damage evolution in laboratory tests at the sample scale. In the last part, an in situ heating experiment is analyzed by using the proposed model. Numerical results are compared with experimental data and field measurements in terms of temperature variation, pore fluid pressure change and induced damaged zone. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

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.