Abstract:

A unique square-bottom pedestal has been adopted in the non-overflow sections of a gravity dam in southwest China. Given the region’s susceptibility to severe earthquakes, the influence of the pedestal on the failure mode and the ultimate seismic resistance capacity of the gravity dam is investigated. An acoustic-solid-coupled damage simulation method is proposed with the acoustic element simulating the reservoir water and the elasto-plastic damage model reflecting the nonlinear characteristics of concrete.The feasibility of this method in predicting structural failure modes is verified by analyzing the Koyna gravity dam under the Koyna earthquake. Comparative analyses between the pedestal section and conventional section reveal similar failure areas in the upstream slope, dam heel, and downstream face. Specific impacts of the pedestal include: new failure zones in the pedestal section; effective reduction of depth and area of the failure zone at dam heel; and generation of two development paths in the downstream failure area of pedestal section. According to the criteria of failure area breakthrough, the ultimate ground motion peak acceleration is 0.50-0.55g for conventional section and 0.55-0.60g for the pedestal section. In conclusion, the bottom pedestal enhances the ultimate seismic resistance capacity of the non-overflow dam section.

Key words: concrete gravity dam, bottom pedestal, acoustic-solid-coupled damage simulation, failure mode under strong earthquake, ultimate seismic resistance capacity