Effects of variability in lateral pipe-soil interaction and pipe initial out-of-straightness on controlled lateral buckling of pre-deformed pipeline

The state-of-the-art method for controlling temperature-induced global lateral buckling of a subsea pipeline is to engineer deliberate buckles at widely spaced locations. These buckles are engineered either by the installation process – i.e. ‘snake-laying’ or by installing subsea structures known as buckle initiators at each intended buckle location. The pre-deformed pipeline is new alternative method that involves continuously pre-deforming the pipeline prior to installation onto the seabed. This pre-deformation causes a significant reduction in axial stiffness and therefore significantly increases the buckle initiation temperature. It also allows thermal expansion to be accommodated throughout the pipe length via expansion of the pre-deformed curvatures, rather than being concentrated at specific buckle locations. This paper presents the influence of two of the variabilities in a pre-deformed pipeline design on the buckling performance: the initial out-of-straightness and the lateral pipe-soil interaction. The results show that the concept of a pre-deformed pipeline is robust and the success of the scheme is not affected by these two uncertainties. The pre-deformed pipeline is shown to be a self-governing system where the maximum strain is self-limited at any location. Pipeline pre-deformation is therefore proven to be a cost effective, safe and valuable tool for controlling pipeline lateral buckling.