| 作成年度 | 2011 年度 |
|---|---|
| 論文名 | CHANGE OF SNOW STRENGTH CAUSED BY RAIN |
| 論文名（和訳） | |
| 論文副題 | |
| 発表会 | the International Symposium Phsics， Chemistry and Mechanics of snow |
| 誌名 | Abstracts of the International Symposium Phsics， Chemistry and Mechanics of snow |
| 巻・号・回 | |
| 発表年月日 | 2011/06/01 |
| 所属研究室／機関名 | 著者名（英名） |
|---|---|
| Snow Avalanche and Landslide Research Center, PWRI | Yoichi Ito |
| Civil Engineering Research Institute for Cold Region | Hiroki Matsusita |
| National Research Institute for Earth Science and Disaster Prevention | Hiroyuki Hirashima |
| Snow Avalanche and Landslide Research Center, PWRI | Yasuhiko Ito |
| Snow Avalanche and Landslide Research Center, PWRI | Noro Tomoyuki |
| 抄録 |
|---|
| Rain on snow events can sometimes be cause of wet snow avalanche. However， the condition for wet avalanche release is not clear since the amount of decrease in snow strength due to the rain is not well measured. In this study， laboratory experiments were carried out in order to investigate the change of snow strength with increasing water content by rainwater percolation. In the experiment， snowpack was artificially prepared that consists of insulation， compacted natural snow (10 cm thick)， thin ice layer formed by water spray below freezing point and artificial snow (0.025 mm diameter and 30 cm thick) from bottom to top. Subsequently， rainfall (2 mm/h) was artificially brought after 22-25.5 h and 49-52 h from the snowpack formation. Snow hardness was measured by push pull force gauge as an indication of the snow strength before and after the each rainfall events. In addition， snow temperature， density and weight water content were measured. Microscopic photographs of the snow particles were constantly taken to observe wet snow metamorphism. During the experiments， room temperature was set to -5°C at the snowpack formation， 3°C at the rainfall and 0°C after the rainfall. After the first rainfall， upper half of the snowpack became moist and rapid decrease was observed in the snow hardness according to empirical relationship between the hardness and water content. The rainwater further penetrated up to the ice layer after the second rainfall; high water content (?23%) was observed above the ice layer， however， the hardness was relatively larger than that expected from its high water content. This is possibly due to the delay of grain coarsening by the rainwater. |
