Study On Lateral Global Buckling Of HP/HT Deep Water Pipeline

With the development of submarine oil and gas resources, research on deep water pipeline global buckling caused by high temperature and pressure in the process of oil and gas transport is becoming a hot issue. Since the pipe holds a great deal of hydrocarbon, once the pipeline buckles or even yields, the hydrocarbon will leak out. This will not only waste resources but also endanger the living conditions of halobios and human beings. Therefore, study on buckling of submarine pipelines under thermal stress is of a great practical significance.This paper utilizes analytical solutions and numerical simulations to analyze the characters of lateral buckling for ideal pipeline, pipeline with single initial imperfection and pipeline with non-single initial imperfections, assumes that the resistance of soil to pipeline is a constant. Many key problems for pipeline lateral buckling have been explained. The main work and results are as follows:(1) Energy method is utilized to calculate the analytical solution of lateral buckling for ideal pipeline and pipeline with single initial imperfection. The accuracy for energy method is verified. Case study shows that, when ideal pipeline happen to lower-order lateral buckling, Model Ⅱ is easier to occur than Model Ⅰ; when ideal pipeline happen to high-order lateral buckling, Model Ⅳ is easier to occur than Model Ⅲ; It is easier to occur ModelⅠbuckling for pipeline with single arch initial imperfection, and pipeline with double arch initial imperfection is easier to occur ModelⅡ buckling.(2) The perfect length of pipeline model for lateral buckling analysis is calculated and the causes of snap buckling in analytical solution are explored. The researches show that the perfect length of pipeline model decreases with the increase of vom/L0. The main cause of snap buckling is that the release amount of axial force is greater than the increase amount of frictional resistance on the condition of pipeline starting to lateral buckling in the small imperfection ratio case.。(3) A combination method for buckle analysis method and explicit dynamic method is proposed. 3D solid elements are established to simulate the soil foundation. Comparisons of two different triggering manners in global buckling are also investigated. The researches show that it is reliable to utilize explicit dynamic method analysis pipeline lateral buckling. Both the initial imperfection and interference force can trigger pipeline global buckling. The results of global buckling triggered by two methods significantly differ.(4) A numerical method is established to analyst lateral buckling of ideal pipeline, pipeline with single initial imperfection and pipeline with non-single initial imperfections. The difference between analytical solution and numerical simulation are presented. The influence of imperfection space and compound modes for lateral buckling are discussed. The researches show that the lateral buckling for pipeline with single initial imperfection is a continuous process, and buckling model develops gradually from low-order model to high-order model. The differences in calculating results obtained by analytical method and results obtained by numerical simulation method are decreasing with vom/L0 increasing. When the adjacent two imperfections are relatively close, there is a superposition phenomenon for pipeline buckling which endangers the stability of pipeline system.