Seismic and impact-pressure monitoring of flowing avalanches
Continuous records have been made during the passage of dry- snow avalanches of both seismic signals, which allows the avalanche speed to be estimated, and impact pressures on load cells with surface areas of 645 and 6450 mm[2]. The impact-pressure recordings show an initial peak followed by a base...
| Published in: | Journal of Glaciology |
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| Main Authors: | , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
1980
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| Subjects: | |
| Online Access: | https://doi.org/10.3189/S0022143000010716 https://nrc-publications.canada.ca/eng/view/ft/?id=56e77616-9c28-4979-a871-5c8e05d790cd https://nrc-publications.canada.ca/eng/view/object/?id=56e77616-9c28-4979-a871-5c8e05d790cd https://nrc-publications.canada.ca/fra/voir/objet/?id=56e77616-9c28-4979-a871-5c8e05d790cd |
| Summary: | Continuous records have been made during the passage of dry- snow avalanches of both seismic signals, which allows the avalanche speed to be estimated, and impact pressures on load cells with surface areas of 645 and 6450 mm[2]. The impact-pressure recordings show an initial peak followed by a base pressure. The observed initial and base pressures vary strongly within avalanches and from one avalanche to another, but, on average, they can be correlated with the frontal speed and the density of the deposited avalanche snow. It is concluded that well-developed dry-snow avalanches have an unsteady wave motion similar to the slug flow observed in ultra-rapid flow of water, and that they consist of three stratified components: dense flowing snow at the bottom, light flowing snow, and powder snow. Des signaux sismiques permettant d'évaluer la vitesse des avalanches et les pressions d'impact exercées sur des cellules dynamométriques d'une surface de 645 et de 6450 mm[ 2] ont été enregistrés de facon continue durant le passage d'avalanches de neige poudreuse. Les pressions d'impact enregistrées indiquent un maximum initial suivi d'une pression normale. Les pressions initiales et normales observées varient grandement pour une même avalanche et d'une avalanche à l'autre, mais, en moyenne, il y a corrélation avec la vitesse de front et la densité de la neige déposée par l'avalanche. Les auteurs concluent que les grandes avalanches poudreuses ont un mouvement ondulatoire instable qui rappelle l'écoulement en bouchon des masses d'eau ultra-rapide. Ces avalanches comportent trois strates: une neige dense et coulante, couverte de neige légère et coulante, elle-même couverte de neige poudreuse. Peer reviewed: Yes NRC publication: Yes |
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