Research on mechanical model for aligning dislocated underwater pipelines during replacement and repair

Submarine pipelines are laid with elastic bending to adapt to the changes in seabed elevation, which usually results in the pipeline being in a pre-stressed state. When replacing and repairing those damaged pipelines, it is easy to encounter rebound and misalignment after pipeline cutting. Therefore, the alignment of the dislocated pipelines must be carried out before replacing and connecting the pipes. At present, some internationally advanced underwater rapid repair equipment only has the function of pipeline lifting, and cannot achieve precise alignment of dislocated pipelines on both sides. It lacks the alignment control model. This article focuses on the alignment problem of dislocated underwater pipelines during replacement and repair. Firstly, based on the Winkler elastic foundation beam and cantilever beam theory, a mechanical model for the alignment of dislocated pipelines is established. Then, an alignment control method is developed based on the mechanical model, and recommended the model's applicability conditions, design parameters, and safe usage range. Finally, the accuracy and reliability of both the alignment mechanics model and control method have been fully verified through numerical method. The established mechanical model and control method in this paper address the crucial issue of aligning misaligned underwater pipelines during repair, providing technical support for engineering applications. And they can be used to guide the design of aligning functional structure for underwater rapid maintenance equipment and also be applied in development of specific alignment schemes for pipeline misalignment scenarios.