An avalanche of insight into granular soil collapse and deposition dynamics

The particle flow physics of granular materials such as sand, gravel, chemical powders, and agricultural grains is relevant to both natural processes, such as avalanches and landslides, and industrial processes like pharmaceutical processing and mining. They are also significant to geological processes elsewhere in the solar system.

Chen et al. investigated how a packing of granular materials collapses and flows from an inclined plane to a horizontal one. Employing a numerical simulation technique, the researchers tracked the motion of each particle to uncover the scaling laws for how far, how fast, and how long the material can travel.

“We were surprised that the same frictional scaling function we developed for granular column collapses on horizontal planes works almost perfectly here, although the finite-size scaling exponents changed,” said author Teng Man.

The researchers also found that the inclination angle plays a major role. For gentle slopes below about 45 degrees, only the top layers flow; above that, the whole mass slides like a rigid block. This transition changes everything, from how far the debris travels to how fast it moves.

“This isn’t just about sand in a lab,” said Man. “The results speak directly to landslides, debris flows, and pyroclastic flows, where granular material on a slope runs out onto a flatter area. The scaling laws for runout distance, front speed, and collapse duration could help forecast those same characteristics for landslides.”

The findings could also inform improved designs for hoppers, chutes, and mining operations.

“Beyond the Earth, the same physics applies to Martian landslides and lunar regolith flows, where gravity is different but the granular behavior follows similar rules,” Man said.

Source: “Collapse dynamics and deposition morphology of granular soils avalanching from inclined to horizontal planes,” by Qinyi Chen, Teng Man, Herbert E. Huppert, Xudong Zhang, Honglei Sun, and Yuanqiang Cai, Physics of Fluids (2026). The article can be accessed at https://doi.org/10.1063/5.0332355 .