| Summary: | 碩士 === 國立中山大學 === 海洋環境及工程學系研究所 === 91 === Abstract
The purpose of this study was to integrate the principle of marine geotechnical engineering, underwater acoustic and optical observation techniques into studying the distribution of seafloor sediments and engineering stability of artificial reefs off Yung-an Harbor, Kaohsiung Country, south-western part of Taiwan. The reefs were deployed to the testing site in November, 1996. The goal of this study was intended to describe the situation of reefs site and confirm whether reefs were moved and buried or not; as well as, to predict whether reefs should be deployed again in the future.
Long-term monitoring of underwater targets was conducted by using of side-scan sonar system, echo sounder, sub-bottom profiler, and underwater camera. The utility of side-scan system was to depict the topography and terrain features of seabed. The other equipments were used to complement and prove the results of side-scan sonar observations. In this study was estimated by Morison’s equation wave force against reef, calculate the scouring depth by Silvester’s experience equation (1974), and figure out the settlement of reefs by Das’s theoretical equation (1990).
The topography of Yung-an reef site is generally gentle and terrain features is monotonous. The Most textures of surficial sediments in this site were sandy silt and some gravel was distributed at south of site. According to result, sandy silt layer is above gravel layer, and the height of sandy silt layer was decreased progressively from the North to the South. The largest height of sandy silt was in set-A(about 2 meters), second one was in set-B(about 1 meters), and set-C was covered by boulder rock and gavel.
Typhoon was the major factor which causes movement and overturning of reefs. Based on theoretical analysis and long term in-situ observations on a testing site, original heaped reef was overturned among the investigated period, and there were no obvious movement and settlement status for non-heaped reefs. Besides, the relationships between reefs and seafloor sediment were arrived dynamic balance after six years. According to difference site, the total depression of reefs was estimated to be 0 to 2 meters, and no any reef was buried.
To sum up, there was no reefs had been buried and moved in set-A, set-B, and set-C on the Yung-an reef site. Furthermore, due to the ability of gathering fishes of artificial reefs, some fish groups surround with reefs. Consequently, in the view of engineering, Yung-an reef site was a suitable site for deploying reefs.
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