Macropore-Driven Infiltration in Frozen Slopes: Large-Scale Experimental Insights with Hydrological and Geotechnical Implications

Frozen soils are typically considered impermeable due to their reduced infiltration capacity. During rainfall, water behavior depends on whether the soil thaws, allowing infiltration, or remains frozen, causing surface runoff that may lead to flooding or debris flows.
Open macropores, such as cracks, root channels, and wormholes, act as preferential flow paths, significantly altering these dynamics. Understanding these processes is crucial for improving hydrological models, evaluating slope stability, and assessing natural hazard risks in cold regions.

To investigate these mechanisms, a novel large-scale experimental setup has been developed, which is up to ten times larger than previous experiments and surpasses them in complexity.
The setup features a tiltable design, adjustable up to 20°, allowing the system to replicate natural slope conditions. An advanced irrigation system ensures automated and uniform rainfall distribution across the surface. Controlled climate conditions are maintained via a sophisticated climate chamber, enabling precise and realistic freezing processes. A macropore pattern plate facilitates the creation of a reproducible macropore network, ensuring consistency across experiments. Additionally, advanced sensors enable 3D visualization of soil temperature and moisture distribution, providing detailed insights into the internal processes during freezing and thawing.
This innovative approach reduces the gap between simplified small-scale experiments and the complexity of real-world scenarios.

Experimental results demonstrate that open macropores, despite their small volume fraction within the soil body, significantly facilitate infiltration and accelerate thawing of frozen slopes, directly influencing the hydrological cycle and slope stability.
The findings provide essential data for validating numerical models under climate-relevant freeze-thaw scenarios.

With the increasing frequency of freeze-thaw cycles driven by climate change, this research is essential for assessing infrastructure risks, managing groundwater resources, and mitigating natural hazards in cold and transitional regions.