2023 Fiscal Year Final Research Report
Study on Convection of driftwood in debris flow using RIM method and measure against bridge clogging due to driftwood
| Project/Area Number |
21K04609
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Review Section |
Basic Section 25030:Disaster prevention engineering-related
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| Research Institution | Meijo University (2022-2023)
Kyoto University (2021) |
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Principal Investigator |
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| Project Period (FY) |
2021-04-01 – 2024-03-31
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| Keywords | RIM法 / 土石流 / パイピング / 流木 / 橋梁閉塞 / 流体力 / 流水阻害率 |
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| Outline of Final Research Achievements |
We investigated the woody debris motion in debris flow using RIM method when the embankment collapses. Second, we revealed the location of the point where a piping occurs and measured the sediment particle velocity at 3 phases. Third, we conducted the driftwood accumulation test at the bridge and examined the effect of the wood length on blockage ratio. We also measured the drag force exerted on the bridge when driftwood accumulates in a narrow river. Finally, we tested a new large wood retention system in which embayment zone is connected to main channel and woody debris is removed when water level rises. The laboratory flume experiments were conducted by varying the elevation of the embayment zone, entrance shape of embayment zone, installation angle of groyne, groyne position, number of groynes and Froude number. The results showed that the trapping probability is highly influenced by the entrance shape of embayment zone.
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| Free Research Field |
河川防災学
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| Academic Significance and Societal Importance of the Research Achievements |
RIM法から盛土崩壊時の土石流の流れ，流木が含まれるときの流木の挙動を調べた．また土石流の原因とされるパイピング現象についてフェイズ分けし，発生位置，土粒子の速度を明らかにした．流木閉塞が起きるときの径間長と流木長の比を明らかにし，橋梁閉塞の起きやすい河川を知るための有用なデータを得た．また流木対策として増水時にのみ機能するわんど域を利用した流木捕捉システムを考案し，対岸の水制も下部を透過型にして平水時に影響の少ない流木捕捉工で80％以上流木を除去することができた．
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