,,- Charles University, Faculty of Science, Institute of Hydrogeology, Engineering Geology and Applied Geophysics, Praha 2, Czechia (tomas.weiss@natur.cuni.cz)
Loess covers approximately 10% of the Earth’s land surface. Despite its ability to maintain vertical cliffs, loess is highly susceptible to rapid internal erosion, leading to the formation of pipes, tunnels, and gullies. These in turn can lead to ground collapse or rapid transport of contaminants. Despite these impacts, the physical process of how these gullies form is not yet fully understood. Our contribution focuses on the effect of confinement, a critical factor for loess stability that has been so far understudied.
This study used a new experimental method where loess blocks were encased in concrete or epoxy to simulate deep-profile conditions. These laboratory simulations revealed a distinct dual behavior: unconfined loess disintegrates rapidly through air slaking upon contact with water, whereas confined loess—restricted from expanding by the surrounding soil mass—maintains its structural integrity and resists erosion even under high hydraulic pressure.
Field validation conducted at a quarry supported these findings. In situ tests demonstrated exceptional cohesion, withstanding hydrostatic pressures of up to 3 meters. The results show that loess collapse and pipe expansion are not continuous but occur only at the onset of flow through them. The results indicate that erosion in loess pipes and tunnels is driven by air-slaking when excess air pressure builds up in pores due to surface tension as water infiltrates previously air-filled pores, not by the seepage force of flowing water. This study shows that any credible experimental setup for cohesive soils must consider the effect of confinement to accurately reflect field conditions.
- Vojtíšek, J., Bruthans, J., & Weiss, T. (2025). Confinement as a key but overlooked factor controlling erosion rate in loess pipes and tunnels. Geomorphology, 109874.
- Vojtíšek, J., & Bruthans, J. (2024). Loess susceptibility to erosion: Interaction of cohesion sources, air slaking and confinement. Earth Surface Processes and Landforms, 49(6), 1821-1835.
How to cite: Weiss, T., Vojtíšek, J., Landa, D.-A., and Bruthans, J.: Confinement as a key factor in loess erosion and stability, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17747, https://doi.org/10.5194/egusphere-egu26-17747, 2026.
