TRIME

Triggering Mechanisms of Snow Slab Avalanches

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 Obiettivo del progetto (Objective)

'Snow avalanche is the most frequent type of slope failure in mountainous areas of the world. In total, approximately 15% of Europe’s and 6% of Earth’s land may be considered as avalanche prone-areas. Avalanches claim hundreds of lives annually worldwide and there have been historical cases with death tolls between hundreds and thousands of people during one event or winter season.

One of the main goals of snow avalanche research is to forecast natural or induced mechanical failure of a sloping layered snowpack in order to estimate potential damage to human activities in mountain regions and to be able to conduct risk-oriented planning. The deadliest type of snow avalanches are slab avalanches, which start from a failure of a cohesive horizon of snow, or “slab”, underlaid by a so called “weak layer”. The nature of weak layer deformation is considered the crux of slab stability. At present, the origin of initial failure and the failure process in the weak layer remain poorly understood.

In order to contribute to development of a mechanical model of snow fracture, and to provide tools to estimate initial conditions for avalanche dynamic models for hazard mapping and risk management, we propose to investigate the mechanical behavior of weak layers and their relationship to slope-scale instability.

Key objectives of the study are: 1) To design instrumental apparatus for both cold laboratory and in situ field work to study the mechanical behavior of snow weak layers. 2) To obtain, through experiment, fully operational mechanical laws of different types of alpine snow weak layers. 3) To critically review existing modeling approaches for weak layer and slab in order to couple best existing practices with experimentally obtained results. 4) To relate the micro and meso-scale weak layer behavior to the macro-scale slab failure by means of numerical modeling for development of a next generation numerical model describing the mechanical behavior of a snow slab on a slope.'

Introduzione (Teaser)

An EU research project has investigated the underlying causes of avalanches, hoping to improve avalanche prediction methods.

Descrizione progetto (Article)

Snow avalanches can be extremely destructive events, and are responsible for hundreds of deaths annually. Despite this, avalanche prediction has not advanced past models developed decades ago.

The EU-funded 'Triggering mechanisms of snow slab avalanches' (http://trime.irstea.fr (TRIME)) project aimed to contribute to a new model of snow fracture events that lead to avalanches. They planned to achieve this through building new instruments, collecting avalanche data and modelling.

TRIME started by building a new apparatus that could measure the properties of the weak snow layer thought to trigger avalanches. This apparatus was used in the laboratory and the field to collect data on the properties of the weak layers within the snow.

Another aspect of the project reviewed over 40 models that have been used in the past for predicting avalanches. Together with the collected data, this review allowed researchers to create a new model of weak layer behaviour under various stressors.

Finally, researchers used avalanche data from Sakhalin (a Russian island) to investigate the causes of avalanches. This research showed that Sakhalin has the most deadly avalanches on Earth, and that this is due to increased colonisation of mountain slopes.

The work of TRIME has moved snow science and the study of avalanches forward through both statistical and experimental approaches. In the long term, this will help to limit the human impact of these dangerous natural disasters.