Submarine Pipeline Buckling On Uneven Seabed And The Stability Of The Submarine Pipeline In Liquefied Soil

With the exploitation of ocean oil and gas resources,more and more submarine pipelines were laid in the ocean.The submarine pipeline stability is directly associated with the continuity and safety of the whole transportation system.The pipelines are under complicated ocean environment,they are influenced by wave,current,high temperature(HT),high pressure and earthquake, which may cause the appearance of instability.The uneven seabed is one of the reasons that cause the upheaval buckling of submarine pipelines.Besides,when submarine pipelines are under partly liquefied seabed,they can easily float upward and then lead to failure.The submarine pipeline with initial imperfection is modeled by using the finite elements analysis(FEA) software Ansys.The non-linear springs are used to modeled pipe soil interaction.The ASCE method is adopted to define the spring stiffness which consider the soil parameters,soil pressure,and diameter of the pipeline.So,the initial imperfection,axial friction coefficient,internal pressure and the above factors are discussed in this paper.The submarine pipelines buried under partly liquefied seabed can have prominent vertical displacement by the buoyancy.So this paper putward three methods which are interval anchors,interval backfill with gravel,interval lay simple portal frame to make the pipeline stable.The finite element model consider the geometric and material nonlinear.The results show that initial imperfection,soil parameters have great influence on upheaval buckling of pipeline,while the internal pressure will not change che buckling process.However, axial friction coefficient have little influence before buckling,but it plays an important role in maintaining the pipeline stability after buckling.The three measures that make pipelines stable can reduce the vertical displacement effectly,but the second method can t decrease the stress of submarine pipelines well.So,this paper recommends the first and the third measures to make the submarine pipeline stable.