The full-scale avalanche test-site at Lautaret Pass (French Alps)

https://doi.org/10.1016/j.coldregions.2015.03.005Get rights and content
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Highlights

  • The instrumentation developed at the avalanche test-site at Lautaret Pass (French Alps) is presented in this paper.

  • The avalanche pressures are measured with load cells and velocity using the correlation of time-lagged optical signals.

  • The avalanche powder cloud is characterized with an ultrasonic anemometer and a snow particle counter.

  • Avalanche positioning is obtained from oblique photogrammetry, and a laser scanner.

  • Avalanche impact pressures are reconstructed from inverse analyses of structure deformations.

Abstract

The full-scale avalanche test site at Lautaret Pass in the southern French Alps has been used by IRSTEA-Cemagref Research Institute since 1972. Over recent years, two avalanche paths have been used routinely to release avalanches and study avalanche dynamics and interactions between avalanches and obstacles. Avalanche flows are generally dense and dry, sometimes with a powder cloud on top. Main avalanche path no. 2 is dedicated to studies on avalanche dynamics. Within the flow of the avalanche, flow height and vertical profiles of pressure and velocity are measured along a 3.5 m tripod. The snow volume released in the release zone is quantified by differential analysis of laser scanning measurements performed before and after triggering. High-speed positioning of the avalanche front along the track is carried out by terrestrial oblique photogrammetry. Above the dense layer, the upper layer of the avalanche is characterized by particle and air flux measurements. Avalanche path no. 1 is smaller in size and particularly well-suited to experiments on structures exposed to small to medium-size avalanches (< 1000 m3). A macroscopic sensor structure consisting of a one square-meter plate supported by a 3.5 m high steel cantilever beam is fixed in the ground, facing the avalanche. Impact pressures are reconstructed from the beam deformations and avalanche velocity is measured by optical sensors. For these experimental devices dedicated to improving our understanding of avalanche physics, a national and international partnership has been developed over the years, including INSA de Lyon, CNRS and Université Joseph Fourier (France), Aalto University (Finland), Nagoya University (Japan), Boku University (Austria) and IGEMA (Bolivia).

Keywords

Avalanche science
Avalanche test-site
Instrumentation
Impact pressure
Avalanche dynamics

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