Research On The Stability Of Submarine Pipline On The Effect Of Wave And Tidal Current On Silty Seabed

The twenty-first century is ocean century. In recent years, the exploitation of marine oil and gas has developed very fast in our nation. Thus, submarine pipelines have been increasing every year. Pipelines transportation is still one of the important transportation modes, delivering oil and gas from offshore platform to land. However, in complex marine environment, bed around pipelines arouse scour easily under the effect of the hydrodynamic terms, such as wave or tidal current, then result in span. The spanning pipelines will lose the supportive force and friction. When the wave or tidal current force acted on, the pipelines will vibrate. This will break the safety and stability of the pipelines extremely.The paper based on physical model tests, studied the force-induced vibration systematically through the phenomenon observed and the data collected in the tests.Research status at home and abroad presently is introduced, including scour of the bed and force-induced vibration, then the characteristic of the paper is brought forward. The conditions and content of the physical model tests are described detailedly. The courses of the scour aroud the pipeline and the formation of sand waves are explained in detail through the close observation of the change in bed, and certain rules are summarized too.The force acted on submarine pipelines in silty bed is analyzed mainly, because the pipelines are generally layed on fine sediments in our country. Through the contrast of different trials, the characteristic of the force influenced by the differences of the wave elements and the burial depth is summarized. Then the influence of the force under current is also analyzed, making up for the lack of the research at home and abroad about the effect under both wave and current.The influence of the force acted on pipelines on different kinds of seabed is studied by the contrast of the three sorts of beds- medium sand, fine sand and silt seabed. The process of the force acted on the submarine pipelines under both wave and current in silty bed is analyzed concretely on above basis. In addition, a new concept- residual force is introduced tentatively, which is used to study the effect in single wave period, in order to explain the development tendency of the pipelines vibration.At last, the mechanism of vortex-induced vibration is expounded. And the vibration fatigue of the pipelines is discussed by applying the survey data of DF1-1 GAS LINE and the general situation of the research area, under typhoon or not. This research will help the installation and the maintenance of the pipelines in the area.