Concrete Face Rockfill Dams in Highly Seismic Regions
Until the Wenchuan earthquake of May 12,2008 no large concrete face rockfill dam(CFRD)was subjected to strong ground shaking.Quite a few dam engineers were of the opinion that CFRDs are inherently safe against earthquakes,because any leakage in the concrete face would not lead to the failure of the dam.Even if such a state could be achieved excessive leakage could not be tolerated and the reservoir would have to be drawn down if severe damage of the concrete face and/or the water proofing system has to be assumed.In this paper the main measures to be considered to achieve a safe CFRD in highly seismic regions are discussed.In mountainous regions the following seismic hazards have to be considered:(1) ground shaking,(2)impact of rockfalls on buildings and dams,(3)impulse waves due to mass movements in the reservoir,(4)large variations in reservoir inflows due to failure of landslide dams or failure or overtopping of smaller dams in the catchment area.Furthermore if active faults are passing through the reservoir or the footprint of the dam then these hazards must also be taken into account.However,these aspects are not addressed in this paper.For the design of a high CFRD in a highly seismic region the following measures are recommended,which improve the performance and the seismic safety of the dam:(l)flat slopes(reduce seismic deformations),(2)generous freeboard (accounts for seismic deformations and impulse waves in the reservoir),(3) wide crest (improves safety of crest region of dam and increases resistance against overtopping from impulse waves),(4) proper material selection in dam body with proper zoning (rockfill shall allow free draining of water leaking through the concrete face),(5)strengthening the downstream slope of crest region of CFRD,(6)provision of a bottom outlet,(7)concrete panel with smaller width to account for non-uniform deformations of the concrete face,(8) arrangement of reinforcement of the face slap to improve its load bearing behaviour in-plane and out -of -plane and to improve its ductility,(9) arrangement of proper joint system including horizontal joints and selection of the joint width to account for the reversible nature of the seismic response,(10)water -proofing system of face slab and the plinth joint,and(11)good compaction of rockfill,etc..
earthquake concrete face rockfill dams seismic design seismic hazard
Martin Wieland
Chairman,ICOLD Committee on Seismic Aspects of Dam Design Poyry Energy Ltd.Hardturmstrasse 161,CH-8037 Zurich,Switzerland
国际会议
The 1st International Symposium on Rockfill Dams(第一届堆石坝国际研讨会)
成都
英文
791-799
2009-10-18（万方平台首次上网日期，不代表论文的发表时间）