A unique square-bottom pedestal has been adopted in the non-overflow sections of a gravity dam in south-west 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 dam-age 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 struc-tural failure modes is verified by analyzing the Koyna gravity dam under the Koyna earthquake.Comparative analy-ses 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;ef-fective 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.
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