Study On Vertical Buckling Of Submarine Pipeline

Oil and gas resources is both major energy resources and important strategic reserve materials which protect a country’s political, economic and military security over the world. It is highly concerned by many countries. With the widespread application of high temperature and high pressure subsea pipeline in offshore engineering, people pay more attention to the safety of pipeline. The paper takes a pipeline in Bohai Sea as an example to study the upheaval flexion of high temperature buried pipeline and its influencing factors. Then the measures of engineering control buckling are summarized and their effectiveness is compared. The research content is as follows:Firstly, the research status and the progress of theory on upheaval buckling of the whole pipeline are systematically summarizes in the paper. The ideal buried pipes and the bucking rules of pipes with initial defects are studied with two types of compressive bar stability theory in classical structural mechanics. The numerations about amplitude and wavelength of initial geometric imperfection are also introduced. And analytic method of theory is applied to calculate the safe temperature of operation on the pipeline.Secondly, according to high temperature submarine pipeline buckling problem, the initial geometric imperfection is introduced by using the method of characteristic structure. The contact finite element model of pipe and soil is established. And then the analytic method of Riks nonlinear buckling is used into the models of different initial defect amplitude to get the rule of the displacement, stress and strain. The contrasting the rule of temperature changing curve and the theoretical results are compared to indicate the correctness of the finite element method.Finally,parameter sensitivity analyses are conducted to analyze the effects of the pipeline material,the geometry of the pipe cross-section,the shape of the initial geometric imperfections, pipe friction coefficient of soil, soil strength and heavy and medium pressure on the seabed temperature sensitive pipe by using numerical simulation method. The subsea pipeline engineering protection measures which commonly used are summed by comparing the high temperature pipes safety and limit temperature. Then the numerical results of natural backfill after trenching, backfill and chain stable compact engineering protection methods are analyzed. Their security and limit of the temperature difference between flexion are obtained, and the effectiveness of engineering controls flexion of three horizontal contrast is measured.