Investigation On Asymmetric Buckling And Collapse Mechanisms Of Deepwater Submarine Pipeline During Installation

The submarine pipeline is an important part of oil and gas exploitation projects. The uniqueness of environmental conditions and design needs determines the unforeseeable risks and challenges. Pipelines inevitably encounter bending and high external pressure during installation in the deep waters. Besides, the existence of material and geometric nonlinearity makes the problem become more complicated. Deepwater pipelines are vulnerable to local buckling, which will, in turn, have the potential of initiating a propagating buckle. The propagating buckle will lead to catastrophic flattening and failure of the whole pipeline, causing huge economic loss. Therefore, the researches focusing on the buckling responses and collapse mechanisms of pipelines have an important engineering significance.Extended from the existent researches of symmetric buckling, a theory, which could effectively predict the asymmetric buckling responses of pipelines with arbitrary initial geometric imperfections, was proposed. Then, a series of investigations on load-carrying capacity and buckling responses of pipelines under different loading combinations and various types of loading paths were carried out. The research work done in this paper can be summarized as follows:(1) The Asymmetric Buckling Theory of Deepwater Pipelines. A theory, which could effectively predict the asymmetric buckling responses of pipelines with arbitrary initial geometric imperfections under bending and hydrostatic pressure as well as the case of combined bending and hydrostatic pressure, was proposed capturing the practical loading characteristics of deepwater pipelines during installation.(2) Finite Element Anslysis of Pipelines. A three-dimension pipeline model was established to analyze the mechanical behavior and buckling responses under bending and hydrostatic pressure as well as the case of combined bending and hydrostatic pressure. The results of the numerical model were then compared to those of the theoretical method to prove the relative effectiveness of the theory.(3) A series of parametric studies, such as load-type, loading path, diameter to thickness ratio, initial geometric imperfection and material properties etc., were carried out to investigate the influences of these factors. Besides, the influence mechanisms of them were discussed in detail.