Although many frost heave and freezing soil models have been developed in the past decades, saturated conditions are commonly assumed and/or the behavior of pore ice rather than ice lenses are conventionally predicted. This study presents a fully coupled thermal-hydraulic-mechanical (THM) model for variably saturated freezing soil, which examines a number of processes. These include heat conduction and convection, phase change, water (moisture) movement through cryosuction, and the development of independent ice lenses. Instead of directly solving for the pore pressure distributions, the void ratio is considered as a dependent variable related to the degree of water saturation. Both the stress-deformation and ice lens segregation are inextricably linked to the evolution of the void ratio as well. The coupled mechanism and performance of the model is first verified by comparison with laboratory freezing experiment observations obtained from literature and then is further evaluated by a series of parametric analyses. The results show that the calculated profiles of temperature, water content and frost heave are in good agreement with literature experimental data, demonstrating that the proposed THM coupling model appropriately represents the mechanisms of heat-moisture-deformation in variably saturated freezing soil. In addition, the sensitivity analysis illustrates that in the test cases considered, thermally-induced cryosuction due to phase change is the main driving force for water migrating towards the freezing front. Also, ahead of the freezing front, a significant increase in effective stress developed due to the elevated negative pore pressure and expansion of ice lenses causing substantial consolidation and reduction in porosity in the unfrozen zone. As the freezing front penetrated with time, the temperature, moisture, vapour and stress-strain fields interact with each other. The distribution of water vapour was mainly controlled by the temperature gradient and location of the freezing front. Both the initial degree of saturation and hydraulic conductivity affected the distribution of pore pressure and displacements. Higher compression moduli and lower overburden load led to greater frost heave but exerted little influence on the temperature field. Finally, the two-sided freezing scenario for soils underlain by permafrost made the middle ice-poor zone highly compacted with ice lenses accumulating near both freezing boundaries.

尽管在过去的几十年中已经开发了许多冻胀和冻结土壤模型，但通常假设饱和条件和/或孔隙冰的行为而不是冰晶状体的行为被常规预测。本研究提出了一种用于可变饱和冻土的全耦合热力水力机械 (THM) 模型，该模型检查了许多过程。这些包括热传导和对流、相变、通过冷冻抽吸的水（水分）运动以及独立冰晶状体的发展。不是直接求解孔隙压力分布，而是将孔隙比视为与含水饱和度相关的因变量。应力变形和冰晶偏析都与空隙率的演变密不可分。该模型的耦合机理和性能首先通过与文献中获得的实验室冷冻实验观察进行比较验证，然后通过一系列参数分析进一步评估。结果表明，计算得到的温度、含水量和冻胀曲线与文献实验数据吻合较好，表明所提出的THM耦合模型恰当地反映了变饱和冻土的热-水分-变形机制。此外，敏感性分析表明，在所考虑的测试案例中，由于相变引起的热致冷冻抽吸是水向冻结前沿迁移的主要驱动力。此外，在冰冻锋面之前，由于增加的负孔隙压力和冰晶状体的膨胀导致未冻结区的大量固结和孔隙率降低，有效应力显着增加。随着冻结锋随着时间的推移而渗透，温度、水分、蒸汽和应力应变场相互影响。水汽的分布主要受温度梯度和冻结锋位置的控制。初始饱和度和水力传导率都会影响孔隙压力和位移的分布。较高的压缩模量和较低的覆土荷载导致较大的冻胀，但对温度场影响不大。最后，