Crashworthiness Evaluation of Reinforced Concrete Duct for Subsea Cable Protection to Stock Anchor Drop Impact

Subsea cables are critical infrastructure that are susceptible to damage from anchor drops, necessitating robust protection systems. This study evaluated the crashworthiness of a duct-type reinforced concrete protection (DRCP) structure subjected to the impact of a 1.27-ton stock anchor. A numerical simulation model was developed using the Coupled Eulerian–Lagrange (CEL)-based fluid–structure interaction (FSI) method to replicate actual collision behavior involving the structure and seabed soil. This numerical approach was validated by conducting full-scale crashworthiness tests under conditions equivalent to a free fall from a water depth of 14 meters. The experimental results confirmed that the DRCP structure maintained global structural integrity, sustaining only localized concrete damage. A quantitative comparison of the key impact parameters between the simulation and test data, including maximum compressive strain, maximum strain rate, effective collision duration, and collision strain energy density, showed an average error range of 14.6% to 27.4%. These deviations fall within acceptable engineering limits for the concrete dynamics. Therefore, the proposed FSI-based simulation is a reliable and cost-effective tool for predicting the impact response of subsea cable protection structures, contributing to the development of safer design standards.