Dynamic coupling mechanism and parametric study of mooring chain–seabed interaction based on a global-to-local nested modeling approach

In deepwater mooring systems, the dynamic interaction between anchor chains and the seabed is critical for controlling chain displacement and mooring anchor capacity, yet its complexity poses significant challenges for accurate simulation. This paper proposes a ‘global-to-local’ nested modeling framework to analyze chain-soil interaction under realistic ocean loads. First, a coupled model of floater-mooring-seabed is established, incorporating the influence of seabed soil properties on the mooring system. Then, using the time-varying loads at the truncation points of the coupled model as boundary conditions, a refined chain-soil model is developed using the coupled Eulerian-Lagrangian (CEL) method, defining the soil deformation patterns and chain configuration, displacement, and tension evolution of the chain during dynamic mooring. Consistency in load-displacement responses between models validates the feasibility of the nested modeling approach. Parametric studies show that the strain rate effect significantly enhances soil resistance and governs soil deformation patterns, while changes in soil ductility and sensitivity also considerably affect the trenching development and system response. This study provides a reliable numerical tool and theoretical basis for the accurate assessment of dynamic responses and safe design of deepwater mooring systems.