Theortical And Experimental Study On Upheaval Bucking Of Steel HT/HP Subsea Pipeline

Offshore oil and gas resources are still the major social sources of energy and offshore oil and gas pipelines are crucial in the development of offshore oil and gas resources because once the pipelines are damaged,not only economic losses but also An unmanageable environmental problem.Due to the substantial increase in operating temperature and pressure of submarine oil and gas pipelines,the overall buckling problem of deep-sea pipelines has become increasingly prominent.During the whole pipe buckling,the shape of the initial defect has an important influence on its response.In particular,the submarine oil and gas pipelines are in a more complex environment where there may be some types of seafloor defects,such as overhangs and vertical bumps.These special topological features of the seafloor will affect the overall buckling of the submarine pipelines.Therefore,this dissertation focuses on the overall buckling problem of subsea pipelines under these flaws.By using numerical simulation,experimental analysis and statistical analysis methods,the author has carried out in-depth systematic studies and obtained some achievements that are of both scientific and engineering significance:The vertical buckling behavior of the pipeline under two vertical defects is studied,including two kinds of symmetrical defects and asymmetrical step defects.A numerical model of the overall buckling of the submarine pipeline under the condition of vertical defects is established and the vertical buckling process is analyzed.The influence of the height of the defect,the bending stiffness of the pipe,and the weight of the pipe on its vertical overall buckling process was analyzed.The critical force calculation formula of the vertical overall buckling of the pipeline under the condition of vertical defects was deduced;on this basis,the design and implementation were carried out.The vertical buckling model test of the pipeline with vertical defects was performed by simulating the actual working conditions of the pipeline through the hot oil flowing inside the pipeline.This test not only verified the correctness of the numerical model,but also verified the dynamics of the pipeline during vertical buckling.The vertical buckling behavior of the spanning pipeline is studied.A numerical analysis model of the vertical overall buckling of the spanning pipeline is established.The vertical buckling process is analyzed,and the span length,the pipe bendingstiffness,and the pipeline itself are analyzed.The influence of weight on its vertical buckling process;combined with the results of numerical analysis,combined with dimension analysis,the critical buckling critical buckling direction force was obtained;on this basis,a pipeline with a span section was designed and carried out.In the vertical overall buckling test,the pipeline was loaded with hot oil to simulate the actual working conditions of the overall buckling process of the pipeline.The test chose the pipe diameter and span length as control parameters,which not only validates the accuracy of the establishment of numerical model,but also lays the foundation for further research.The application of the statistical learning model in the analysis of the vertical overall buckling of the submarine pipeline was studied.The linear regression model,the decision tree model,and the random forest model were used to model the critical buckling critical deflection force of the pipeline.The training model had good results.Accuracy can be used to guide engineering practice.