Influence of water level on RC caisson subjected to underwater explosions

Abstract

With the increasing significance of marine safety issues, the studies on the underwater blast-resistant performance of wharves, e.g., reinforced concrete (RC) caissons, has become an urgent demand. At present, the influence of water level on caisson subjected to underwater explosions was studied experimentally and numerically, e.g., underwater explosion loading characteristics and dynamic behaviors of caisson. Firstly, four shots of underwater explosion test were carried out both in free field and on a partially submerged caisson specimen, and the overpressure- and deflection-time histories, as well as the structural damage pattern were recorded. Then, the underwater explosion loading characteristics including the preceding blast wave and the succeeding bubble oscillations, the cut-off effect of the water surface, as well as the dynamic behaviors of caisson are comprehensively discussed. Furthermore, both the 1D and 3D finite element (FE) models were established, and by adopting Coupled Eulerian-Lagrangian method and remapping technology, the reliability of the FE models and analysis approach were validated by comparing with the test results. Finally, the influence of water level on the dynamic behaviors of caisson against underwater explosions were numerically examined. It derives that, the empirical formula derived based on spherical charge for underwater explosion peak overpressure is applicable to group charge, while the formula for impulse provides higher prediction on group charge; bubble oscillation has great influence on the impulse of underwater explosions; the unsubmerged part of hydraulic structures suffers slighter damage during underwater explosions than submerged part; the upper part of caisson is more sensitive to the change of water level; the partially submerged caisson shows better blast-resistant performance than fully submerged caisson. The present work could provide helpful reference for the studies on the underwater explosion loadings, as well as the blast-resistant assessment and design of hydraulic structures.