Submarine Pipeline Lateral Global Buckling and Buckling Failure Critical State Discussion

Due to high temperature and pressure,unburied or shallow buried submarine pipelines experience lateral global buckling. Excessive bending caused by uncontrolled deformation may threaten the safety of the pipeline system. Thus,the integer of a post-buckling pipeline section should be assessed under design temperature and pressure differences. This study focuses on the post-buckling pipeline safety assessment.First,a series of model tests based on sand obtained from Bohai Gulf were proposed,and soil resistance to pipelines with different embedment are measured. A dynamic soil resistance model with varying pipeline embedment and lateral displacement was established. The influence of embedment on peak soil resistance and residual soil resistance was analyzed. Second,the critical buckling forces of pipelines with different imperfections were analyzed. A"critical force range"was proposed to evaluate whether the pipeline exhibits lateral global buckling or not. Third,the limit state of a post-buckling pipeline in an engineering case was assessed. The assessment was proposed based on both load control condition and displacement control condition. Further comparisons show that pipelines reach their limit state according to load control condition far more quickly than according to displacement control condition.