1988 Fiscal Year Final Research Report Summary
Study of the rapid densification process of wet snow and water soaked snow
| Project/Area Number |
62460044
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
気象・海洋・陸水学
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| Research Institution | Hokkaido University |
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Principal Investigator |
WAKAHAMA Gorow Institute of Low temperature Science, Professor Hokkaido University, 低温科学研究所, 教授 (90001643)
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| Co-Investigator(Kenkyū-buntansha) |
KOBAYASHI Shun'ichi Research Institute of Hazards in Snow Areas, Professor Niigata University, 積雪地域災害研究センター, 教授 (70001659)
NARITA Hideki Institute of Low Temperature Science, Lecturer Hokkaido University, 低温科学研究所, 講師 (20001662)
IZUMI Kaoru Research Institute of Hazards in Snow Areas, Associate Professor Niigata Univers, 積雪地域災害研究センター, 助教授 (50114997)
MOTOYAMA Hideaki Institute of Low Temperature Science, Research Associate Hokkaido University, 低温科学研究所, 助手 (20210099)
YAMADA Tomomi Institute of Low Temperature Science, Lecturer Hokkaido University, 低温科学研究所, 講師 (50002100)
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| Project Period (FY) |
1987 – 1988
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| Keywords | Densification / Wet snow / Soaked snow / Firn / Perennial snow patch / Compression / Creep test / 帯水層 |
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| Research Abstract |
Rapid densification process of wet snow and soaked snow was investigated by field observations and experiments in the laboratory. In the bottom of Hisago perennial snow patch in Daisetsu Mountain, ice body in the thickness of 5 m is formed and, on the ice body, unconfined aquifer exists by meltwater percolation. Firn soaked by water in the aquifer is compressed by the pressure of depositional snow over it for long time from the snow melting season (from May). The speed of densification is approximately three times larger than that of usual wet snow and finally its wet density increase to over 0.83 g/cm^3. It is made clear that the mechanism of the formation of ice body in the snow patch is due to frozen of this high density firn by the coldness starting in the beginning of winter. As the experiment, the creep test in constant compressive stress was mainly made using the water soaked snow. The range of pressure applied is situated between 0.1 to 2.0 kgf/cm^2. The densification speed, that is, strain rate is almost independent to the grain size distribution of snow and increases rapidly with increasing pressure. In the range of the pressure more than 1 kgf/cm^2, which is nearly yield stress of ice, the dependency of strain rate to pressure is shifted, i.e., the speed of densification increases drastically. While the logarithmic value of strain rate linearly decreases with increasing of snow density, the linearity suddenly changes at a limited density corresponding to the change of the densification mechanism. Led from the experiment is the empirical equation, by which the time required in the densification from snow to ice, which density is 0.83 g/cm^3, can be estimated at a given pressure. The experimental investigation for wet snow densification is remained in future study.
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