1996 Fiscal Year Final Research Report Summary
STUDY ON RELEASE CONDITIONS AND DISASTER PREVENTION OF SLUSHFLOW
| Project/Area Number |
07680483
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Natural disaster science
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| Research Institution | NIIGATA UNIVERSITY |
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Principal Investigator |
IZUMI Kaoru Niigata University, Research Institute for Hazards in Snowy Areas, Associate Professor, 積雪地域災害研究センター, 助教授 (50114997)
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| Co-Investigator(Kenkyū-buntansha) |
KOBAYASHI Shun'ichi Niigata University, Research Institute for Hazards in Snowy Areas, Professor, 積雪地域災害研究センター, 教授 (70001659)
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| Project Period (FY) |
1995 – 1996
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| Keywords | SLUSHFLOW / SLUSH / AVALANCHE / AMOUNT OF RAINFALL / SNOW-MELTING / MOUNTAIN STREAM |
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| Research Abstract |
Slushflow disasters occurred in Japan were found out from the database of newspaper articles and their characteristics were investigated on the site. The following results were obtained in the 1996 fiscal year.
Two conditions are required for the slushflow release ; (1) plenty of snow accumulation in the mountain stream, (2) rapid increase of stream water by rainfall and snow-melting. Snow accumulation in the mountain stream is divided into next three categories ; (1) natural snow deposit due to less running water, (2) debris deposit by avalanches, (3) artificial deposit by falling snow from roofs or roads. The occurrence of a slushflow due to a collapse of snow dam built by avalanche debris in mountain stream requires an accumulated amount of rainfall over several hundred millimeters. But natural snow deposit in a stream can release as a slushflow even by several ten millimeters rainfall.
At Mt.Fuji slush-avalanches have occurred in four consecutive winter seasons. A history of slush-avalanche at Mt.Fuji since sixteenth Century was completed in the chronological order by the investigation of historical documents and on-site survey of slush-avalanche accidents in recent years.
As our experimental study shows that the fluidity of slush depends on the amount of contained water, it is considered to be effective for preventing slushflow to lower the fluidity of slush by draining water out rapidly from the slush at the early stage of flow. And our experiments of impact force of slush reveal that the construction in a slushflow stream smaller than the scale of coagulation of slush like a bridge pier should be strengthened in the case it might not resist the impact force of slushflow.
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