風化花崗岩斜面の調査
スポンサーリンク
概要
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Every year many sediment disasters have occurred on decomposed granite slopes which are distributed in western Japan. We carried out field survey and simultaneous natural radioactivity and electrical prospecting in order to understand the characteristic of collapses on decomposed granite slopes. From the results, following matters proved to be clear.1. The results of the investigation of the devastation in Nakatsuoka river basin, the western part of Hiroshima city are as follows.(1) The average length of collapse is 12.9m and below 20m is 87%. The average width of collapse is 7.6m and below 10m is 83%. The average volume of collapse is 120m3 and below 200m3 is 86%.(2) The average angle of inclination is 41.3° and 30° -50° is 92% (291 out of 317 spots).(3) The persentage of collapse in this basin is 80 spots/km2.(4) The volume of collapses is about 24, 000m3/km2.Those are considered the typical examples of decomposed granite slopes wthich are distributed in and around Hiroshima city.2. As a result of these investigations, it was proved that checkdam works are effective for disaster prevention and mitigation systems.3. We suggest that it is better to make investigation of the natural radioactivity and the electrical prosrecting at the same time in order to find deradational slopes. It is considered that the area of high radioactivity and low specific resistivity is degradational ground.As an actual proof we can show the index of slope stability and the predictability of collapse at Ohgusa area and Hitotsukojima district in Hiroshima Prefecture.
- 社団法人 日本地すべり学会の論文