The Study On Protective Rock Berms To Subsea Pipelines Against Dragging Anchors

In recent years, as the inland oil resource dried up, offshore oil and gas industry have been developing very fast. As a result, the applications of subsea pipelines are widespread. However, there are a lot of ships go through the area of subsea pipelines. We can see several accidents that subsea pipelines were damaged by anchors in the past years. This condition makes the research on subsea pipeline protection urgently.There are many engineering measures to protect pipelines, and it is economical to excavate an inverted trapezoidal trench and bury pipelines under rock armour berms in the trench. Nowadays, there is little research about the protective effect and mechanism of this protective structure at home and abroad.Ten tests were carried out in a large test flume using three sizes of anchor models. In the process of test, the anchor was dragged horizontally moving from sand into rock berms. By measuring the vertical displacement and dragging force, the moving process was realized. Therefore, the protective effect of rock armour berms was proved fine. By observing the process of anchor and analyzing the forces based on Coulomb’s earth pressure theory, the protective mechanisms were obtained.After that, finite element software ABAQUS was used to build anchor and soil models. The soil could be coupled to Eulerian instance, so that the process of drag could be simulated. The calculated results were coincident to those of tests, which can also confirm the protective effect of rock berms and prove that this kind method of simulation was applicable.