Study on influence of dam foundation damage on seismic safety of gravity dam under combined action of main shock and aftershock

Abstract

The existing seismic design codes for hydraulic structures have not yet required to consider the impact of strong aftershocks on the secondary damage caused by the dam. However, the actual earthquake damage indicates that the impact of strong aftershocks cannot be ignored. In order to study the seismic safety of concrete gravity dam subjected to strong earthquakes, this paper constructs a constitutive model that reasonably reflects the dynamic damage evolution process of dam concrete based on damage mechanics theory. According to the similarity of concrete and rock material, the concrete damage model is extended to the rock mass material. Based on this, taking the gravity dam as an example, the overall damage mechanics model of the dam body and the dam foundation is established. According to the characteristics of the dam site and the characteristics of ground motion, the artificial seismic wave with time-frequency non-stationary characteristics is synthesized considering the attenuation law of ground motion duration and intensity envelope function. The effects of main shock and strong aftershock on the whole damage of gravity dam are studied. The results show that the strong aftershock after the main shock has different cumulative effects on the overall damage and plastic strain of the gravity dam. The gravity dam will further expand in the damaged area when subjected to strong aftershocks. The cumulative effect of the aftershock on the damage and plastic strain of the foundation is more significant than that of the dam. Therefore, it is necessary to consider the plastic damage of the dam and the dam foundation in the seismic analysis of the dam.