Dynamic Response and Damage Modes of Caisson Wharves Subjected to Underwater Contact Explosions

This study investigates the dynamic response and damage assessment of caisson walls under underwater contact explosions through scaled experiments and numerical simulations. A fluid-structure interaction finite element model was developed in LS-DYNA and validated against experimental results. The validated model was employed to conduct parametric analysis, elucidating the influence of explosive charge mass, wall thickness, and reinforcement ratio on structural response. The results identify two primary failure modes: localized damage characterized by concrete spalling and diagonal cracking, and global failure involving structural overturning. A strongly nonlinear, three-stage degradation pattern of residual load-bearing capacity as charge mass increases is revealed. Furthermore, the critical failure thresholds including wall thickness and reinforcement ratio are determined. Finally, a practical damage assessment methodology is proposed, which introduces a dimensionless damage index D based on residual load-bearing capacity. A three-level classification criterion is established, which shows excellent agreement with experimental observations. The findings of this study provide valuable insights and a reliable tool for the blast-resistant design and post-explosion safety evaluation of caisson wharf structures.