1991 Fiscal Year Final Research Report Summary
Study on armoring mechanism of river bed surface with sand and gravel mixtures
| Project/Area Number |
02650361
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Hydraulic engineering
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| Research Institution | Ehime University |
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Principal Investigator |
SUZUKI Koichi Ehime Univ., Faculty Eng., Professor, 工学部, 教授 (70026285)
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| Co-Investigator(Kenkyū-buntansha) |
SHIMUZU Yoshihiko Gunma Univ., Faculty Eng., Research Associate, 工学部, 助手 (70178995)
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| Project Period (FY) |
1990 – 1991
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| Keywords | sand mixture / bed materials / mobile armoring / static armoring / fining / vertical sorting / longitudinal sorting / grain size distribution |
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| Research Abstract |
The grain size distribution of bed surface in an experimental flume are observed under the equilibrium condition of sediment discharge. Based on the experimental results, the armoring mechanism for the equilibrium bed of sediment discharge with mixtures of sand and gravel is roughly divided into three categories :
1) mobile armoring for low flow intensity,
2) dynamic armoring- for medium flow intensity, and
3) fining for- extremely high flow intensity.
The mechanism for each armoring phenomenon is analyzed qualitatively and the characteristics of the grain size change with bed shear stress are revealed.
The mechanism of the armor coat formation which occurs during the degradation of river bed downstream of a dam is explained by a newly proposed vertical sorting model of coarse and fine sand for the rotational degradation of the river bed. And the armoring of the bed for the parallel degradation is explained by the well known longitudinal sorting model. And these proposed models are experimentally proved to be reasonable for the explanation of the armor coat formation on the surface of degrading river bed.
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