Objective During ship anchoring operations, anchor chain dragging poses a major external threat to submarine pipelines, often leading to bending, buckling, or even rupture failure. While most existing research focuses on anchor-soil interactions or local pipeline damage, there is a lack of systematic study on overall pipeline bending instability induced by dragging loads, particularly regarding the influencing mechanisms and coupling effects of multiple factors. Therefore, elucidating the damage mechanisms of submarine pipelines under multi-factor coupling and analyzing the influencing law of each factor can offer a scientific basis for designing safety protection measures.

Methods Two typical X60 submarine pipelines operating in Hangzhou Bay were selected for study. The pipe-soil interaction forces and anchor dragging forces were calculated using DNV codes. Based on ABAQUS finite element software, an anchor dragging analysis model incorporating pipe-soil interaction was established. Parametric analyses were performed to systematically examine the effects of dragging load angle, soil type, seawater flow velocity, and pipeline radius-thickness ratio on pipeline stress, strain, and displacement.

Results Increasing the dragging load angle reduced the pipeline’s maximum Mises stress but increased the maximum displacement, with a marked acceleration in displacement growth beyond θ = 30°. This was attributed to the vertical force component lifting the pipeline off the seabed and weakening soil restraint. The soil stiffness proved critical: muddy clay offered the weakest restraint, resulting in the highest stress, strain, and displacement, while gravelly soil provided the strongest resistance and best protection, significantly reducing the pipeline’s mechanical response. The seawater flow velocity indirectly affected the pipeline by increasing the water flow resistance of the anchor chain; higher velocities attenuated dragging force, thereby reducing pipeline stress, strain, and displacement. A higher radius-thickness ratio increased the pipeline’s sensitivity to mechanical response, with a notable interaction with seawater flow velocity, especially under low-flow-velocity conditions.

Conclusion Submarine pipeline damage from anchor dragging arises from the complex interplay of factors such as dragging load direction, soil restraint, seawater flow velocity, and radius-thickness ratio. Hard soils like gravelly soil provide significant restraint and reduce pipeline deformation, making them preferable in engineering applications, while in-situ soft soils should be avoided for direct backfilling. Enhancing soil restraint effectively mitigates the risk of bending moment-dominated instability. These findings offer a critical foundation for the protective design of submarine pipelines in complex marine environments.