The Mecanism And Solution Of Subsea Pipeline Suspension In Bohai Gulf

There are a lot of sand ridges and sand ripples on the sea bottom in Bohai Gulf,leading to undersea topographical changes.Undersea sandpits are able to change flow field around pipelines.The goal of this article is not only to study the change because of undersea sandpits around the pipelines,but also to find out one structure to protect pipelines from washing out.Compared with other sea areas,because of sandpits and serious overall scouring seabed,the phenomenon of existed subsea pipeline span caused by scouring often arises and it makes serious trouble to pipeline operation safety.Presently,research on span subsea pipeline protection at home and abroad mostly focus on single seabed soil parameters and single protection measures,and the research of comprehensive protection technology of span subsea pipeline under the condition of overall scour seabed and silt/soft clays is less and lack.After studying about the initiation of sediment motion and Fluid dynamics,Numerical model is set up to find the impact of sandpits on pipelines,with pipelines above or under seafloor.The study found that diameter of pit has an affect on the wash degree and that the height between the pipe and the seafloor can also change the flow field and the wash degree around the pipe.Concrete mattress cover,a new structure to protect pipelines from washing out,is studied in this article.Five types of concrete mattress cover models are set up to find out which is the best kind and protect pipelines well.For the force on concrete mattress cover may increase the load of ship during construction,models are built to calculate in the article to make sure it is safe.