Sediment transport characteristics around a spur dike installed on the rigid bed
| Autor: | KYUKA, Tomoko, TAKEBAYASHI, Hiroshi, FUJITA, Masaharu |
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| Jazyk: | japonština |
| Rok vydání: | 2012 |
| Předmět: | |
| Zdroj: | 京都大学防災研究所年報. B. 55:427-436 |
| ISSN: | 0386-412X |
| Popis: | 水制工はその周りに局所洗掘や土砂の堆積を促すため，単調化した河川環境を修復する手法の一つとして注目されている。本研究では，水制のこうした機能が固定床化の進行した河川環境の修復にも有効であるかを評価するため，水理実験と数値解析から水制周りの流れ，流砂・河床変動特性を再現した。この結果，固定床上に設置された水制は移動床上の水制と異なり，その下流域に殆ど土砂を堆積させなかった。これは，固定床では水制周りが局所洗掘されず，水制上流域に無次元限界掃流力以下の領域が広く形成されるためである。流砂は水制上流域で対岸側へと流向を変え，水制周辺まで到達しない。このため，水制周辺には流砂を水制下流域へと輸送する方向の流れが形成されるものの，土砂は堆積しないといえる。ただし数値解析では，流れの非定常性を考慮すると流砂の輸送方向が変わるため，水制間の土砂交換が促される可能性も示された。 Spur dike which is set on movable bed is expected to create new aquatic habitats according to produce local scour and sediment deposition area. In this study, we focused on rigid bed and discussed whether spur dikes will be able to create sediment deposition area on the rigid bed. Experimental flume tests and numerical analysis were conducted to confirm the characteristics of flow, sediment transport and bed deformation around spur dikes on rigid bed. These results showed that sediment was not deposited in downstream area of spur dikes, because shear velocity is too smaller than the critical shear stress in upstream wide range of a spur dike. As a result, all bed materials were transported to the opposite bank side. Thus spur dike on rigid bed didn't promote to deposit sediment in the downstream area of a spur dike. However numerical analysis showed the possibility that unsteady flow promotes to deposit sediment in the downstream area of a spur dike, because the large transverse water surface gradient was formed in the downstream area of a spur dike during water discharge increase. |
| Databáze: | OpenAIRE |
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