Three-dimensional and real-scale modeling of flow regimes in dense snow avalanches

Xingyue Li,Betty Sovilla,Chenfanfu Jiang,Johan Gaume

doi:10.1007/s10346-021-01692-8

Xingyue Li, Betty Sovilla + Show 2 more

Open Access

https://doi.org/10.1007/s10346-021-01692-8

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Abstract

Snow avalanches cause fatalities and economic loss worldwide and are one of the most dangerous gravitational hazards in mountainous regions. Various flow behaviors have been reported in snow avalanches, making them challenging to be thoroughly understood and mitigated. Existing popular numerical approaches for modeling snow avalanches predominantly adopt depth-averaged models, which are computationally efficient but fail to capture important features along the flow depth direction such as densification and granulation. This study applies a three-dimensional (3D) material point method (MPM) to explore snow avalanches in different regimes on a complex real terrain. Flow features of the snow avalanches from release to deposition are comprehensively characterized for identification of the different regimes. In particular, brittle and ductile fractures are identified in the different modeled avalanches shortly after their release. During the flow, the analysis of local snow density variation reveals that snow granulation requires an appropriate combination of snow fracture and compaction. In contrast, cohesionless granular flows and plug flows are mainly governed by expansion and compaction hardening, respectively. Distinct textures of avalanche deposits are characterized, including a smooth surface, rough surfaces with snow granules, as well as a surface showing compacting shear planes often reported in wet snow avalanche deposits. Finally, the MPM modeling is verified with a real snow avalanche that occurred at Vallée de la Sionne, Switzerland. The MPM framework has been proven as a promising numerical tool for exploring complex behavior of a wide range of snow avalanches in different regimes to better understand avalanche dynamics. In the future, this framework can be extended to study other types of gravitational mass movements such as rock/glacier avalanches and debris flows with implementation of modified constitutive laws.

Highlights

Gravitational mass movements cause tremendous damages in mountainous regions all over the world
Aiming at simulating the variety of flow regimes reported in dense snow avalanches and offering quantitative proof for the regime characterization, we analyze the features of the snow avalanches in cases I∼IV from release to deposition, including failure pattern after avalanche release, density variation during the flow, and deposition texture
The failure pattern is associated with the stress state of snow particles, which helps distinguish the amount of fractures developed in snow avalanches and the type of the fractures

Summary

Introduction

Gravitational mass movements cause tremendous damages in mountainous regions all over the world They are all driven by gravity, their behavior may differ much from one another due to notably different constitutions (e.g., rock, soil, water, ice) and mechanisms of motion (e.g., fall, slide, flow). At the release of snow avalanches, there are two major patterns observed in the field: a fracture line and a point release which distinguish slab avalanches and loose snow avalanches, respectively. These distinct release types are primarily controlled by snow cohesion. (Issler et al 2020) identified avalanche deposits including blocky and sharply bounded deposit, snow clods, and finegrained snow. These diverse behaviors make snow avalanches fantastic phenomena which involve challenging research questions with substantial societal and economical impacts

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