Abstract: The dynamic responses of concrete gravity dam under impact loading are much more complicated than that under static loading. In this paper the damage characteristics of gravity dam is researched by applying steel uniform impact to simulate the cyclic impact of wave loading underwater on concrete gravity dam. Geometrical and gravity similitude are both satisfied in the model test. The dynamic responses of model dam are obtained, and the position and propagation of cracks are observed and tracked. Results reveal that when the dam is subjected to cyclic uniform impact loading, the maximum strain of dam is at the middle of the upstream dam face rather than at the dam heel; cracking damage occurs first at the jetty head which is a weak part of impact resistance. The failure modes of concrete gravity dam under cyclic uniform impact include cracking, fragmenting, spalling and throwing. The results provide theoretical basis for the operational management, shock resistance and safety evaluation of dams.

Key words: concrete gravity dam, impact load, cyclic impact, response characteristics, failure modes