Journal topic
https://doi.org/10.5194/tc-2020-83
https://doi.org/10.5194/tc-2020-83

Submitted as: research article 28 Apr 2020

Submitted as: research article | 28 Apr 2020

Review status
This preprint is currently under review for the journal TC.

# The mechanical origin of snow avalanche dynamics and flow regime transitions

Xingyue Li1, Betty Sovilla2, Chenfanfu Jiang3, and Johan Gaume1,2 Xingyue Li et al.
• 1School of Architecture, Civil and Environmental Engineering, Swiss Federal Institute of Technology, Lausanne, Switzerland
• 2WSL Institute for Snow and Avalanche Research, SLF, Davos, Switzerland
• 3Computer and Information Science Department, University of Pennsylvania, Philadelphia, USA

Abstract. Snow avalanches cause fatalities and economic damages. Key to their mitigation entails the understanding of snow avalanche dynamics. This study investigates the dynamic behaviors of snow avalanches, using the Material Point Method (MPM) and an elastoplastic constitutive law for porous cohesive materials. By virtue of the hybrid Eulerian-Lagrangian nature of MPM, we can handle processes involving large deformations, collisions and fractures. Meanwhile, the elastoplastic model enables us to capture the mixed-mode failure of snow, including tensile, shear and compressive failure. Using the proposed numerical approach, distinct behaviors of snow avalanches, from fluid-like to solid-like, are examined with varied snow mechanical properties. In particular, four flow regimes reported from real observations are identified, namely, cold dense, warm shear, warm plug and sliding slab regimes. Moreover, notable surges and roll-waves are observed peculiarly for flows in transition from cold dense to warm shear regimes. Each of the flow regimes shows unique flow characteristics in terms of the evolution of the avalanche front, the free surface shape, and the vertical velocity profile. We further explore the influence of slope geometry on the behaviors of snow avalanches, including the effect of slope angle and path length on the maximum flow velocity, the $\alpha$ angle and the deposit height. Unified trends are obtained between the normalized maximum flow velocity and the scaled $\alpha$ angle as well as the scaled deposit height, reflecting analogous rules with different geometry conditions of the slope. It is found the maximum flow velocity is mainly controlled by the friction between the bed and the flow, the geometry of the slope, and the snow properties. In addition to the flow behavior before reaching the deposition zone, which has long been regarded as the key factor governing the $\alpha$ angle, we reveal the crucial effect of the stopping behavior in the deposition zone. Furthermore, our MPM model is benchmarked with simulations of real snow avalanches. The evolution of the avalanche front position and velocity from the MPM modeling shows reasonable agreement with the measurement data from literature. The MPM approach serves as a novel and promising tool to offer systematic and quantitative analysis for mitigation of gravitational hazards like snow avalanches.

Xingyue Li et al.

## Interactive discussion

Status: open (until 01 Jul 2020)
Status: open (until 01 Jul 2020)
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Xingyue Li et al.

## Data sets

Supplementary data for "The mechanical origin of snow avalanche dynamics and flow regime transitions" X. Li, B. Sovilla, C. Jiang, and J. Gaume https://doi.org/10.5281/zenodo.3764829

## Video supplement

Supplementary videos for "The mechanical origin of snow avalanche dynamics and flow regime transitions" X. Li, B. Sovilla, C. Jiang, and J. Gaume https://doi.org/10.5281/zenodo.3764802

Xingyue Li et al.

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Latest update: 02 Jun 2020