Objectives  With the continuous development of deep-sea marine resources, pipe-laying vessel in submarine pipeline laying task plays a very important role, so it is necessary to carry out the ability analysis for the operation capacity improvement of shallow water pipe-laying vessels.

  Methods  Based on the "ZHONG YOU HAI 101" pipe-laying vessel lifting operation capacity project, SESAM and Orcaflex software is used to analyze the interaction between the vessel mooring system and pipeline when the operating depth is increased. The impact of the presence of the pipeline on the properties of the vessel mooring system is considered, and the effects of various lengths of sag-bend of the pipeline on the vessel mooring system are analyzed. In addition, the effects of ship motion on the tensile stress strain and bending stress strain of the pipeline are studied.

  Results  The results show that the pipeline has great impact on the hull motion and the force of the anchor cable, and various lengths of sag-bend of the pipeline has great influence on surge motion of the vessel and cable tension, while the heave motion of the vessel has the greatest impact on the stress of the pipeline.

  Conclusions   The findings of this study can provide theoretical and basic assessment references for the pipe-laying vessel operation capacity improving project.