The Evolvement Character Of The Seafloor Sandwave In The Northern South China Sea

This study is based on the background of the vigorous development of offshore petroleum exploitation in China.As a result of the development of economic and the urgent need of energy, the exploitation of the oil and gas under coastal continental shelf is substantial increasing. As a carrier to deliver oil and gas from offshore platform to land, submarine pipeline has many merits, such as continuously deliver, convenience management and so on. And it has been used extensively in ocean engineering. However, submarine pipeline is often under severe conditions, especially the effect of wave and tide, may cause the pipeline to be suspended and lose its stability, finally, lead to break. These all bring a great threat and challenges on the seabed oil exploitation and environmental security.The author figures that the causes of the submarine pipeline suspend, of course, including the partial seabed erosion, and fall short of the construction technique. But the root cause is large-scale remotion of the sandwave. At the present time, the research on the sandwave is still on the restricted area by virtue of the surveyed data. In marine works, we need to study the sandwave movement mechanism in a large area via the mathematical models. The content of this paper is expanded on this. At the beginning of this article, a brief review of tide and wave theory is made. Meanwhile, the study of the sediment movement is expounded. Then the causes, patterns and movement mechanism of the sandwave are discussed. On this basis, the mathematical model of the north of South China Sea is established, and then the form and movement mechanism of the sandwave is calculated, the results indicate that the movement speed of the sandwave is relatively small under normal current conditions. So this region can be regarded as a relatively stable type of landscape. These results provide a theoretical basis that the submarine project can be successfully implementation. Further, it is indicated that, although low probability, the sandwave will occur a large displacement under storm waves. Therefore, it is necessary to take observation and forecasting of the storm in the project area.