Item: LOADING ON STRUCTURES FROM FLUIDIZED AVALANCHE FRONTS OVERFLOWING DEFLECTING DAMS AT FLATEYRI, ICELAND, JANUARY 2020
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Title: LOADING ON STRUCTURES FROM FLUIDIZED AVALANCHE FRONTS OVERFLOWING DEFLECTING DAMS AT FLATEYRI, ICELAND, JANUARY 2020
Proceedings: International Snow Science Workshop 2024, Tromsø, Norway
Authors:
- Kristín Martha Hákonardóttir [ Ministry of the Environment, Energy and Climate, Reykjavík, Iceland ] [ Verkís Consulting Engineers, Reykjavik, Iceland ]
- Ragnar Lárusson [ Verkís Consulting Engineers, Reykjavik, Iceland ]
- Árni Kristjánsson [ Verkís Consulting Engineers, Reykjavik, Iceland ]
- Gunnlaugur Pétursson [ Verkís Consulting Engineers, Reykjavik, Iceland ]
Date: 2024-09-23
Abstract: This study back-calculates impact pressures in two dry slab avalanches that were released on a 700 m high mountain above the village of Flateyri in Northwestern Iceland in January 2020. The avalanches were released from distinct starting zones, located east and west of the village. They partially overflowed two 14–20 m high deflecting dams by 150 m and 300 m, respectively. The total mass of the avalanches was estimated 116·106 kg and 150·106 kg, respectively. Radar measurements, avalanche deposit density, and structural damage suggest that the portion of the avalanches that overran the dams (10% of the total mass) belonged to a fluidized region with intermittent density. Type 1 deposits (dense core) were found upstream of the dams, whereas Type 2 deposits (fluidized flow) were located on the lee side, extending to a maximum run-out position, here termed "T2". Type 3 deposits (suspension) reached the sea. Observations of the Flateyri avalanches provide unique insights into the interaction between powder snow avalanches with a strongly fluidized front and deflecting dams. Furthermore, these observations illustrate the physics of the fluidized front in the run-out zone of the avalanche path, particularly its separation from the denser core by the dams. This paper analyzes damaged structures, back-calculates impact pressures, and discusses periodic pressure pulses and brief compression shocks. The focus is on: (1) a partially snow-filled reinforced concrete house with broken windows and doors, and a damaged roof, located 100 m from the top of the dam; (2) three partially snow filled vehicles that were damaged and moved 13 to 20 m laterally; (3) a steel mast on top of the deflecting dam that was broken in two pieces but not dislocated; (4) the mast’s radar antenna that was transported 280 m without damage; and finally (5) a timber shed that shattered, 280 m from the dam and 30 m from T2.
Object ID: ISSW2024_P7.10.pdf
Language of Article: English
Presenter(s): Kristín Martha Hákonardóttir
Keywords: Snow avalanches; powder-snow avalanches; snow avalanche deposit; fluidized front; field observations
Page Number(s): 932 - 939
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