Prediction of Pipeline Roll During S-Laying

During S-laying a pipeline on the seafloor, the pipe is subjected to plastic strains over the stinger of the laying boat. The residue curvature may result in pipe axial rotation, which causes concerns about the orientation of the valves or connections. This paper presents two approaches to predict the pipe roll. The first approach idealizes the pipeline as a pre-bent helix by the residue curvature stretched on the solid floor. The second approach is a 3-D model, simulating the process of the pipe roll during the laying procedure in a quasi-static manner. The pipe loading path and deformation history are fully considered. Other factors, such as soil conditions, can be included. Empirical graphs for the pipeline axial roll versus a normalized residue curvature is established, by which the roll can be preliminarily estimated and the sensitivity of the roll to various parameters is explicitly expressed.