The reliability of pre-deformation to control lateral buckling of pipelines: An evaluation based on observed embedment trends

Pre-deformation of a pipeline into a continuous sinusoidal wave-like form has been shown to be effective at controlling lateral buckling of subsea pipelines due to a substantially lower axial stiffness and the limiting of maximum strain at any location. This paper explores the feasibility and reliability of using such an approach, with an existing operating pipeline, which was installed using zero-radius bend (ZRB) initiator structures, used for comparison. Survey data of the pipeline profile and seabed bathymetry are adopted along with the pipe-soil interaction (PSI) inputs from the original design allowing a like-for-like comparison of the two approaches to management of lateral buckling. The comparison shows that, for the assumptions made in the numerical modelling, use of a pre-deformed pipeline results in lower strain than using ZRBs. Furthermore, the performance of the pre-deformed pipeline is robust, and shown to be unaffected by uncertainties in horizontal out-ofstraightness, PSI input and seabed features. This study shows that pre-deformed pipelines can be an effective alternative for controlling the lateral buckling of subsea pipelines, which eliminates the need for buckle initiation structures to be installed along the pipeline route. This provides impetus for further work on installation methodologies to create the required level of pre-deformation.