Lateral Global Buckling High Order Mode Analysis Of Submarine Pipeline Under HPHT

With the development and utilization of offshore oil and gas resources，as well as theincreasing design requirements of submarine pipelines, the seriousness of globalbuckling failures of pipeline under high temperature and high pressure is increasinglyhighlighted, which has attracted the attention from researchers, engineering andtechnical personnel at home and abroad. Under the combined effect of inner pressureand temperature loads, the pipeline generated additional stress internally. Because thepipeline is constrained by the foundation soil, it can’t make free-form deformation torelease the internal force, and with the increase in length of the pipeline, its internaladditional stress continues to accumulate, eventually leading to a global buckling ofthe pipeline, to the unburied or semi-buried submarine pipelines, lateral globalbuckling is the main form of deformation. Generally, submarine pipelines are notideal flat state. Because of the uneven seabed or encountering rocks when lying andother reasons, the submarine pipeline has initial deformation, which is initialimperfection.By using the analytical solution, this paper derived the high-order lateral buckling andanalyzed the regularity of global buckling of the submarine pipeline which has initialimperfection under the combined effects of temperature and pressure. first ofall,according to the classical methods of the global buckling of submarine pipeline,this paper established the theoretical analysis method of high-order lateral globalbuckling and carried out the analytical solution of one-arch and anti-symmetrictwo-arch by using small deformation theory. Then, based on practical projects, thispaper analyzed the influence of the presence of initial deformation, the forms of initialdeformation, the amplitude of initial deformation and strength properties offoundation soil towards the lateral global buckling of the pipeline, and then, comparedand analyzed the property of buckling. At last, by using VC++, this paper developed asoftware to calculate the lateral global buckling of the subsea pipeline, it can analyzeand calculate the lateral global buckling under four different modes of the idealpipeline and the defective pipeline, and then, it can draw the curve of pipelinebuckling deformation and the curves between temperature difference, buckling forceand initial imperfection amplitude.Conclusions gained through research are as follows: The higher the frictioncoefficient is, the higher the safety temperature of global buckling of pipeline will be; the higher the amplitude of initial deformation is, the lower the temperature differenceof global buckling of pipeline will be; the safety temperature of the high-order globalbuckling is lower than the safety temperature of the low-order global buckling, Inother words, the high-order global buckling occurs more easily; the pipeline withinitial imperfection global buckling occurs more easily.