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.

Freshwater ecosystems are vulnerable to the invasion of exotic aquatic plant species because of the great likelihood of the introduction of exotic species, and the lack of barriers that block introduced species. Water hyacinth, Pontederia crassipes Mart., is one of the world's most invasive alien plant species damaging freshwater ecosystems worldwide. Here, we monitored the water hyacinth population on Jeju island, Korea, to assess current invasion risks. Furthermore, we investigated how water hyacinth affects water pH because pH is an important determinant of the distribution of other aquatic plants, and thus a good indicator of aquatic ecosystem health. Water containing water hyacinth had a pH of 5.3, while that with water hyacinth and soil had a pH of 4.8 72 hours after the start of the experiment. Water hyacinth extracts contained shikimic acid, stearic acid, and palmitic acid, which are possible compounds that caused a decline in water pH. Water hyacinth also inhibited the growth of the aquatic plant species, Spirodela polyrhiza and Lemna perpusilla. These results imply that invasion of water hyacinth adversely impacts the abiotic and biotic characteristics of aquatic ecosystems. Moreover, monitoring the water hyacinth population suggests that this invasive aquatic plant overwinters on Jeju island. Therefore, regular monitoring and subsequent control of water hyacinth population can prevent its expansion in the aquatic habitats of Jeju island and the southern region of the Korean peninsula.

The Loess Plateau is highly susceptible to gully headward erosion, highlighting the urgent need for soil stabilization. In this study, a series of physical and mechanical properties, water physical properties and microstructure tests were carried out to explore the loess improvement for potential control of headward erosion in loess gullies. Experimental results reveal that the addition of the Consolid System to loess soil leads to an increase in the plastic limit and liquid limit of the soil, while the soil retains its characteristics as a type of low plasticity soil. The dry density of the stabilized loess soil decreases, while the unconfined compressive strength increases. Regarding the water-physical properties, the swelling and shrinkage properties of modified loess soil were significantly improved while the permeability coefficient slightly decrease. Furthermore, the surface energy decreased, resulting in increased water repellency, while the pore volume remains relatively unchanged. A recommended minimum mixing ratio of the Consolid System is 1.5% to resist water erosion. In conclusion, the implementation of the Consolid System not only enhances the strength of loess soil and its water repellency, but also preserves the advantageous water drainage characteristics inherent to loess soil. Consequently, loess soil stabilized by the Consolid System holds promising potential for applications in areas covered with loess soil.

Long-term freeze-thaw cycles have a significant impact on the safety and durability of tunnels located in cold regions. In this study, a hydro-thermal-mechanical coupling model and calculation method were developed based on the Guanjiaoshan Tunnel. The model's precision and rationality underwent comprehensive validation. The study aimed to discuss the temporal and spatial distributions of temperature, water, and mechanical fields under long-term freeze-thaw cycles. The findings revealed that the water migration influence zones can be classified into three distinct zones. The ice-water phase change and stress exhibit periodic fluctuations following an annual cycle. Significantly, the lining's stress, or danger level, exhibited two peaks during the autumn and spring seasons. The magnitude of the autumn peak exceeded that of the spring peak. Throughout the initial 12year period, the tunnel's danger level consistently remained below the threshold value of 1.0, affirming its adherence to safety standards during its early service period. Furthermore, the construction of tunnels has the potential to contribute to frozen soils expansion in specific zones due to prolonged freeze-thaw cycles. These study results not only enhance our understanding of hydro-thermal variations but also provide valuable insights for predicting the long-term security performance of tunnels in cold regions.

Alpine permafrost environments are highly vulnerable and sensitive to changes in regional and global climate trends. Thawing and degradation of permafrost has numerous adverse environmental, economic, and societal impacts. Mathematical modeling and numerical simulations provide powerful tools for predicting the degree of degradation and evolution of subsurface permafrost as a result of global warming. A particularly significant characteristic of alpine environments is the high variability in their surface geometry which drives large lateral thermal and fluid fluxes along topographic gradients. The combination of these topography-driven fluxes and unsaturated ground makes alpine systems markedly different from Arctic permafrost environments and general geotechnical ground freezing applications, and therefore, alpine permafrost demands its own specialized modeling approaches. In this work, we present a multi-physics permafrost model tailored to subsurface processes of alpine regions. In particular, we resolve the ice-water phase transitions, unsaturated conditions, and capillary actions, and account for the impact of the evolving pore space through freezing and thawing processes. Moreover, the approach is multi-dimensional, and therefore, inherently resolves the topography-driven horizontal fluxes. Through numerical case studies based on the elevation profiles of the Zugspitze (DE) and the Matterhorn (CH), we show the strong influence of lateral fluxes in 2D on active layer dynamics and the distribution of permafrost.