Study on the Influence of Water Level and Gallery Polyurea Coating on Dynamic Damage of a Gravity Dam

To improve the safety performance of gravity dams under explosive loading, this study systematically investigates the effects of water level variation, gallery structure, and polyurea antiseepage coating on the dynamic damage behavior of the dam body. The findings reveal that the presence of a gallery alters the propagation path of stress waves within the dam, resulting in localized pressure increase and stress concentration, which exacerbate damage in surrounding areas and reduce overall structural stability. Nevertheless, stress wave reflection at the blasting face of the gallery reduces damage on the upstream water-contact surface. Lowering the water level significantly mitigates damage at the dam crest, water-contact face, and heel, thereby enhancing the overall blast resistance of the dam—an effect more notable than that achieved by changing the blast initiation location. Furthermore, applying a polyurea antiseepage coating to the gallery surface effectively reduces the stress concentration and further improves both the stability and blast resistance of the dam structure.