This study is an attempt to suggest a new state system of permafrost monitoring, primarily for energetic infrastructure, based on past approaches and achievements in Russia for over a hundred years of Arctic studies. The methodology of this study is based on general theoretical methods of scientific research. Historical (retrospective analysis of the development of the monitoring system of long-term permafrost in Russia) and logical (inductive generalization) methods were applied. The structure and methods of permafrost monitoring in the Soviet Union and new technologies used nowadays to establish permafrost monitoring systems, taking into account modern Arctic energetic development, have been analyzed.

Frost heaving in soils is a primary cause of engineering failures in cold regions. Although extensive experimental and numerical research has focused on the deformation caused by frost heaving, there is a notable lack of numerical investigations into the critical underlying factor: pore water pressure. This study aimed to experimentally determine changes in soil water content over time at various depths during unidirectional freezing and to model this process using a coupled hydrothermal approach. The agreement between experimental water content outcomes and numerical predictions validates the numerical method’s applicability. Furthermore, by applying the Gibbs free energy equation, we derived a novel equation for calculating the pore water pressure in saturated frozen soil. Utilizing this equation, we developed a numerical model to simulate pore water pressure and water movement in frozen soil, accounting for scenarios with and without ice lens formation and quantifying unfrozen water migration from unfrozen to frozen zones over time. Our findings reveal that pore water pressure decreases as freezing depth increases, reaching near zero at the freezing front. Notably, the presence of an ice lens significantly amplifies pore water pressure—approximately tenfold—compared to scenarios without an ice lens, aligning with existing experimental data. The model also indicates that the cold-end temperature sets the maximum pore water pressure value in freezing soil, with superior performance to Konrad’s model at lower temperatures in the absence of ice lenses. Additionally, as freezing progresses, the rate of water flow from the unfrozen region to the freezing fringe exhibits a fluctuating decline. This study successfully establishes a numerical model for pore water pressure and water flow in frozen soil, confirms its validity through experimental comparison, and introduces an improved formula for pore water pressure calculation, offering a more accurate reflection of the real-world phenomena than previous formulations.

Water migration behavior is the main cause of engineering disasters in cold regions, making it essential to understand its mechanisms and the resulting mechanical characteristics for engineering protection. This study examined the water migration process during soil freezing through both experimental and numerical simulations, focusing on the key mechanical outcomes such as deformation and pore water pressure. Initially, a series of controlled unidirectional freezing experiments were performed on artificial kaolin soil under various freezing conditions to observe the water migration process. Subsequently, a numerical model of water migration was formulated by integrating the partial differential equations of heat and mass transfer. The model’s boundary conditions and relevant parameters were derived from both the experimental processes and existing literature. The findings indicate that at lower clay water content, the experimental results align closely with those of the model. Conversely, at higher water content, the modeled results of frost heaving were less pronounced than the experimental outcomes, and the freezing front advanced more slowly. This discrepancy is attributed to the inability of unfrozen water to penetrate once ice lenses form, causing migrating water to accumulate and freeze at the warmest ice lens front. This results in a higher ice content in the freezing zone than predicted by the model, leading to more significant freezing expansion. Additionally, the experimental observations of pore water pressure under freeze–thaw conditions corresponded well with the trends and peaks projected by the simulation results.

Оценка изменения несущей способности мерзлых грунтов при возможном изменении температуры и оттаивании вечной мерзлоты в арктической зоне Российской Федерации к середине XXI века

Research on methane and carbon dioxide emissions mainly focuses on industrial emissions, cultivated land, and wetlands, while few studies have studied freezing-related emissions. This paper presents field experiments conducted during soil freezing to measure carbon dioxide and methane concentrations in the air, near the soil surface, and in the soil. In addition, the influence of precipitation, snowfall, air temperature, and depth of freezing on gas emissions was analyzed. We observed increased concentrations of methane and carbon dioxide in soil and air at soil freezing and snow cover growth. For the first time, an increase in gas flux during soil freezing was found in the absence of permafrost.