Research Of Buckling Collapse Of Pipeline Under Torsion And Hydrostatic Pressure And The Arresting Performance Of Combined Buckle Arrestors

This article aimed at the buckling collapse and buckling propagation of deep-water subsea pipelines,quasi-static loading and dynamic loading were respectively analyzed by hydrostatic fluid element loading-method and dynamic implicit algorithm,which were verified by comparing the results with the test data of the full-scale chamber.The simulation model of pipeline under hydrostatic pressure was established and the buckling pressure and buckling propagation pressure under different loading methods were obtained.It was found that due to some factors such as unloading rate and pre-buckling loading conditions,there would be differences between buckling propagation pressure under quasi-static and dynamic analysis.For the analysis of buckling mechanics of pipelines under real sea conditions,the applicability of the two calculation methods needs to be further verified by sea trial thus the procedures of sea trial of deep-water pipelines were also designed.The buckling collapse mechanics of pipelines under torsion and hydrostatic pressure were specially studied.For pipelines subjected to torque,the calculation equation of pipelines under torsion in elastic stage was derived through the establishment of theoretical analysis model,which was verified by finite element analysis.The riks-method is used to establish the simulation model of pipelines under torsion and hydrostatic pressure.By applying different torsion and load-paths to the pipeline,two cross-section deformation modes and three overall deformation modes of the pipeline were obtained,and the causes of the different deformation modes were analyzed.The sensitivity analysis of the pipeline under torsion and hydrostatic pressure was carried out.It was found that factors such as the thickness,ovality,outer diameter,material properties and different load-paths would significantly impact the collapse pressure of pipelines.By using an optimized network prediction method,the pipeline collapse pressure was fitted and predicted,which provided a more convenient calculation method for the design and study of pipelines.Participated in the design of a reduced-scaled chamber which can apply torque and hydrostatic pressure to pipelines,as test procedures for buckling collapse of pipelines under different load-paths was designed.At present,the study of buckle arrestors is still focusing on single ones.The model of slip-on and spiral buckle arrestors were established and optimized by numerical simulation.The accuracy of the model was verified by the test results,based on which the two models of parallel arrestor and overlay arrestor were put forward.Sensitivity analysis of these two kinds of combined arrestors was carried out.The effects of the length,number of turns,wall thickness,spacing and winding methods of the arrestors on the crossover pressure of arrestors were studied.Two different crossover modes were obtained.By comparing the crossover pressure of these types of arrestors,the arresting performance of the combined arrestors was studied,as its advantages and practicality were discussed,which could be helpful for offshore oil development.