Chapter 1 - General description

Abstract

The general overview of high concrete arch dam construction and its seismic situation in China are briefly introduced. China is a country of high seismicity with abundant hydropower resources. A series of arch dams of about 300-m high are being under construction and will be constructed in the severe seismic regions of western China for flood mitigation and clean energy supply. Dam construction plays an irreplaceable role, but any accident of serious damage of high dam with huge reservoir during the unavoidable strong earthquake can induce unimaginable secondary catastrophe to surrounding communities. The significant importance of the study on seismic safety and the strategic priority of preventing seismic catastrophe of secondary disaster for high dams with huge reservoirs are explained. Also, the basic ideas of the seismic safety evaluation implemented now in China are presented. The evaluation of seismic safety for any engineering structures should include following indispensable and intermatching components, such as: seismic input, earthquake responses of structure, and dynamic resistance capacity of material. The behaviors of major high concrete arch dams subjected to earthquakes both in China and abroad, including the 113-m high Pacoima concrete arch dam subjected to the 1971 San Fernando earthquake of magnitude 6.6 and the 1994 Northridge earthquake of magnitude 6.8 and a 130-m high Sharpei roller-compacted concrete arch dam subjected to the 2008 Wenchuan earthquake of magnitude of 8.0 in China, are investigated and analyzed. Some lessons learned from them are discussed. The existing engineering practice and the analyses of strong earthquake cases of dams have demonstrated that for dams well-designed according to the seismic design cord and elaborately constructed, their desired seismic safety would be basically anticipated. However, for the super high dams of about 300 m having no precedent to go by, the challenge of a series of critical technical thorny problems have yet to be faced for dam earthquake engineers.