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 present work investigated the macrostructural and microstructural changes in the behavior of two different soil samples collected from Rayaka (Su-1Clay) and Dodka (Su-2Clay) in Vadodara, Gujarat, India, under multi-staged oedometer tests. The microstructural analysis was performed to understand the pore morphology and particle rearrangement for different stress cycles and durations. For interlinking the macroscopic and microscopic data, porosity and void ratio were compared for both levels, and results showed an average deviation of 6%. From the mineralogical data, illite group minerals were predominant in both the samples and similar macroscopic behavior was observed during the multi-staged tests. The pore count was found to be higher during the initial stages of consolidation, as there was no stress involved. The microscopic results for Su-2Clay indicated that the loading patterns, load duration and plane of observations (i.e., parallel or perpendicular to loading) do not influence the circularity of pores and shape ratio. It was observed that the particle rearrangement was influenced by their loading value and duration, plane of observations and loading patterns. As a result, the behavior of most of the particles changed from anisotropic to isotropic as the stress value and time increased.

The present study investigated the evolution of the time-dependent behavior of remolded samples of Indian black cotton soil for different loading-unloading-reloading cycles in oedometer conditions. The microstructural analysis was carried out to evaluate the parameters such as particle rearrangement and pore size reduction that are responsible for creep at different time periods. It was observed that micropores existed in large numbers, and the number of pores decreased rapidly with an increase in pore size. The number of pores was found to decrease by 20-30% and 85-90% at the intermediate and final stages of the creep test, respectively. Additionally, it was noted that although small pores and mesopores were less in number, they were significant in pore area calculations. The reduction in pore areas for the intermediate and final stages was found to be in the range of 40-50% and 40-60%, respectively, as there were large proportions of micropores that compressed without influencing the overall pore area. The percentage of vertically aligned particles reduced from 21 to 15% at the end of the test. This observation is attributed to the particle rearrangement and reduction in pore sizes that occurred during the test.