Abstract: The stratification characteristics of seabed soils significantly influence the reverse catenary properties of the installation line and the trajectory of the drag anchor. Theoretical analysis and derivation establish models for the reverse catenary shape and drag force of the installation line in layered clay. Degradation verification and comparative analysis demonstrate the validity and necessity of the established theoretical model. Based on the coupled Eulerian-Lagrangian method, the drag force theoretical model is integrated into the finite element model via a user subroutine, creating a large deformation finite element analysis method for the interaction among the installation line, drag anchor, and layered seabed. A sensitivity analysis of the subroutine parameters determines the optimal value of the key parameter ΔT/tc, comparing with existing numerical analysis and small-scale model test results. The results indicate that, compared to homogeneous clay, the stratification characteristics of soil lead to more complex variations in drag force, thereby affecting the anchor trajectory. Compared to the direct modeling approach for the installation line, the proposed method enhances computational efficiency by 56.64%.

Key words: installation line, drag anchor, layered clay, motion trajectory