Lateral Global Buckling Failure Assessment For Exposed Submarine Pipeline

With the development of economy, the demand for oil and gas resources is increasing, and the development of offshore oil resource is valued highly. As a safe, efficient, and economic means of transportation, submarine pipeline has been widely used in offshore oil and gas engineering. O il and gas are typically transported under high pressure and temperature, both of which induce global buckling in pipelines. Excessive global buckling impairs the integrity of a pipeline and affects the pipeline service performance. This paper focus on the submarine pipeline lateral global buckling and buckling failure assessment, and the main researches are as follow:The existing methods for lateral global buckling and buckling failure assessment are summarized and compared. A model test is carried out to establish the dynamical pipe-soil interaction model for shallow buried pipeline, and a FEA model is calibrated based on the test results. A method which simulates the dynamical pipe-soil interaction in global buckling numerical analysis based on the secondary development of ABAQ US software by compiling the user subroutine VFRIC is illustrated, and two numerical simulation analysis models which respectively used penalty method and the user subroutine VFRIC are compared to reveal the influence of soil resistance on pipeline global buckling. The pipeline global buckling failure envelope is proposed, and envelopes with different parameter combination are analyzed by using numerical simulation analysis.These study show that:(1) The critical buckling of pipelines with initial imperfection of v0/L0?0.15 % can be assessed by comparing the relative magnitudes of the actual load and the range of critical buckling force;(2) When assessing post-buckling pipeline with initial imperfection, load failure is stricter than displacement failure in the assessment of failure in post-buckling pipelines;(3) The model test results reveal that initial penetrometer influences the development of soil resistance, and pipeline with larger initial penetrometer has a larger peak value of soil resistance but have a same residual value with small initial penetrometer;(4) A comparison of FEA models with different soil resistance shows that the model used dynamical pipe-soil interaction suffers larger critical buckling force, bending moment, strain and more concentrated defo rmation, and the development of deformation and force exists sudden change due to the influence of soil resistance peak value;(5) Pipeline thickness mainly affects brust pressure difference pb, and has little influence on maximum failure temperature Tmax and the area surrounding by envelopes. Soil resistance and calculation length affect the area surrounding by envelopes, and has little influence on the shape of normalized envelopes. Diameter affects the shape of envelopes and the area surrounding by envelopes. Pipeline with larger diameter, larger calculation length, greater soil resistance and thinner thickness is more likely to fail after global buckling.