A Numerical and Energy-Based Prediction Framework for Hall Anchor Penetration in Soft-over-Stiff Clays

The accurate prediction of anchor penetration depth is critical for assessing the potential risk of emergency anchoring to subsea infrastructure. In this study, a three-dimensional coupled Eulerian–Lagrangian (CEL) model was developed to investigate the dynamic penetration behavior of a Hall anchor in homogeneous clay and soft-over-stiff layered clay. The model was validated against published experimental results and showed good agreement with measured penetration depths. For homogeneous clay, an energy-based prediction model was proposed by introducing a resistance modification coefficient, and the relationships between this coefficient and soil strength parameters were established from CEL simulations. The proposed model accurately predicted the penetration process and final penetration depth, with errors generally within ±5%. For layered clay, the evolution of the resistance coefficient revealed three penetration stages: initial impact energy dissipation, penetration through the upper soft layer with increasing resistance, and penetration of the lower hard layer with approximately constant resistance. An energy loss coefficient and layer-dependent resistance formulations were subsequently introduced to develop a simplified prediction model. Comparisons with CEL results demonstrated that the proposed model effectively predicts anchor penetration behavior under various soil strength conditions and impact velocities, with most errors within 10%. The proposed approach provides a computationally efficient tool, reducing the computational cost from hours of CEL simulation to seconds of engineering calculation, for the rapid assessment of penetration depth for Hall anchors with similar geometric characteristics under soft-over-stiff layered clay seabed conditions.