| Qingdao Institute of marine geology, China Geological Survey | Host |
| Citation: |
Changxiang CHEN, Lihua CAO, Zhenye ZHUANG, Jishang XU, Shunliang YANG, Dongbo ZHAO. YINGDONG SAND RIDGES IN EAST BEIBU GULF ANDTHEIR IMPACT ON PIPELINE ENGINEERING[J]. Marine Geology Frontiers, 2018, 34(4): 49-55. doi: 10.16028/j.1009-2722.2018.04007
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YINGDONG SAND RIDGES IN EAST BEIBU GULF ANDTHEIR IMPACT ON PIPELINE ENGINEERING
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Abstract
The Yingdong tidal sand ridge, which occurs in the east of Beibu gulf, is a part of the Qiongxinan sand ridge system. It is well developed outside the Ganen Cornor and smmothly extends to Dongfang. The sand ridge area can be divided into three sections, the deep water flat section, the current ridge and sand wave section and the nearshore section, from the offshore to the coast. In the current ridge and sand wave section, there are four sand ridges in NS or NW-SE direction roughly parallel to the main flow. The ridges are about 45km long with a large width. The valleys between ridges are usually 20-30m in depth, while the ridge top is 5-8m below sea level. Sand valleys are asymmetrical, steep on the land side and gentle on the sea side. The sand ridges were formed in the period of low sea level in Holocene and then eroded by modern wave. The foundation of sand ridge is strong and firm. Only in case of storm wave or strong current, can the surface sediment move in a small distance. In 2003, the Dongfang 1-1 seafloor pipeline was constructed, which passed through the Yingdong tidal sand ridge. Through the analysis of the Dongfang 1-1 offshore pipeline survey data acquired by OUC after construction, it is found that there are 130 points where the pipeline are suspended. The suspended part is 33m long on average and the distance between the pipe and the sea bottom is 1m in maximum. The suspension of pipeline is caused by the changes in bedforms and/or water dynamics. -
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References
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Changxiang CHEN, Lihua CAO, Zhenye ZHUANG, Jishang XU, Shunliang YANG, Dongbo ZHAO. YINGDONG SAND RIDGES IN EAST BEIBU GULF ANDTHEIR IMPACT ON PIPELINE ENGINEERING[J]. Marine Geology Frontiers, 2018, 34(4): 49-55. doi: 10.16028/j.1009-2722.2018.04007
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- Figure 1. Zonal distribution of bedforms in the study area (from reference [3])
- Figure 2. The distribution of sand ridges in the study area
- Figure 3. The bathymetric map and cross sections of the study area (See Fig. 1 for location)
- Figure 4. (a) Lateral flow erosion of sand ridge caused pipe suspension; (b) The steep slope of the sand ridge is eroded by underflow that caused the suspension of the pipe. The black line is the bottom of the sea surface, the red and blue line is the upper and lower edge of the pipe, the yellow part is the suspended pipe; (c) 3D(left) and sonar(right) figures around KP80.2
- Figure 5. (a) The sand dunes enlarged during storm surge, and the valleys deepened when the pipe suspended (A. normal weather; B. the storm surge); (b) Sections around KP88.5, the black line is the bottom of the sea surface, the red and blue lines are the upper and lower boundaries of the pipeline, the yellow part is the suspended pipe; (c) The multibeam image around KP88.5, The pipeline passes through the barchan dune area and the crater between sand ridges
- Figure 6. (a) The schematic diagram of piping erosion effect; (b) The seafloor sonograms of the small sand flow of a circular crater caused by current