Bending Failure Mode and Prediction Method of the Compressive Strain Capacity of A Submarine Pipeline with Dent Defects

A dent is a common type of defects for submarine pipeline. For submarine pipelines, high hydrostatic pressure and internal pressure are the main loads. Once pipelines bend due to complex subsea conditions, the compression strain capacity may be exceeded. Research into the local buckling failure and accurate prediction of the compressive strain capacity are important. A finite element model of a pipeline with a dent is established. Local buckling failure under a bending moment is investigated, and the compressive strain capacity is calculated. The effects of different parameters on pipeline local buckling are analyzed. The results show that the dent depth, external pressure and internal pressure lead to different local buckling failure modes of the pipeline. A higher internal pressure indicates a larger compressive strain capacity, and the opposite is true for external pressure. When the ratio of external pressure to collapse pressure of intact pipeline is greater than 0.1, the deeper the dent, the greater the compressive strain capacity of the pipeline. And as the ratio is less than 0.1, the opposite is true. On the basis of these results, a regression equation for predicting the compressive strain capacity of a dented submarine pipeline is proposed, which can be referred to during the integrity assessment of a submarine pipeline.