| Project/Area Number |
14350269
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
水工水理学
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| Research Institution | HIROSHIMA UNIVERSITY |
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Principal Investigator |
HIBINO Tadashi Hiroshima University, Graduate School of Engineering, Associate Professor, 大学院・工学研究科, 助教授 (50263736)
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| Co-Investigator(Kenkyū-buntansha) |
KOMAI Katsuaki Hiroshima University, Graduate School of Engineering, Research Associate, 大学院・工学研究科, 助手 (90314731)
OZAKI Noriatsu Hiroshima University, Graduate School of Engineering, Associate Professor, 大学院・工学研究科, 助教授 (50294541)
高橋 暁 産業技術総合研究所, 海洋資源環境研究部門, 主任研究員 (30357371)
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| Project Period (FY) |
2002 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥12,100,000 (Direct Cost: ¥12,100,000)
Fiscal Year 2005: ¥2,700,000 (Direct Cost: ¥2,700,000)
Fiscal Year 2004: ¥2,700,000 (Direct Cost: ¥2,700,000)
Fiscal Year 2003: ¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 2002: ¥4,400,000 (Direct Cost: ¥4,400,000)
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| Keywords | pore water movement / high turbidity layer generation / upwelling of floating mud / DO Respiration / ground water level / stratification / weight of sea water / 高濁質層の形式 / 底泥の巻き上げ / 海底浮遊泥 / 堆積密度 / 間隙水流動 / 採泥器 / 栄養塩 / 巻き上がり / 閉鎖性海域 |
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| Research Abstract |
By investigating the sediment at the sea bottom of the Hiroshima Bay, we were able to show the seasonal change mechanism of the sediment with the pore water movement.
The turbidity increasing does not only depend on the velocity above the bottom but also on the movement of pore water in the consolidated sediment. According to the experiment, the fluid mud doesn't well up when the velocity of under 6cm/s is occurred above the bed. In these results, the bottom flow, observed at the head of Hiroshima Bay, cannot cause the upwelling of the bottom sediment.
Wet density, water content and specific gravity in surface sediment seasonally changed in over 20 cm depths. Water content increased more from summer to fall, and was over 500% at the fluid mud layer in fall. The high turbidity is generated in water content increasing period.
The generation process of the high turbidity is hypothesized that firstly, the pressure different between sea and ground generates in the stratified season because of the water heating etc., secondly, the pore water moves cyclically with tide, finally, the fluid mud wells up with the pore water flowing up from the sediment.
In the consolidated sediment, DO above the sediment are consumed resulting to oxygen-deficient water mass occurs at the sea bottom. According to the numerical simulation, the estimated amounts of the pore water moving explain the turbidity variation and water content profiles of the sediment. These phenomena can be explained by the pore water movement between the sea above the bottom and the sediment layer.
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