In China,an increasing number of high concrete face rockfill dams(CFRDs)are located in high intensity earthquake zones,some of which are close to the seismic fault line.Recordings suggest that near-fault ground motion...In China,an increasing number of high concrete face rockfill dams(CFRDs)are located in high intensity earthquake zones,some of which are close to the seismic fault line.Recordings suggest that near-fault ground motions are characterized by large one-sided velocity pulses.The conventional dynamic analysis of dams,however,neglects the features of strong ground movements.In this study,under different ground motion levels some numerical dynamic studies considering the one-sided broadband pulses of near-fault earthquakes are presented for CFRDs based on a generalized plasticity model for rockfill materials.The results indicate that the displacements of dam crest corresponding to positive and reverse input of near-fault ground motion make a significant difference,while the displacements of the dam crest under artificial seismic waves are similar.Furthermore,using the horizontal and vertical components as simultaneous excitations near the faults,the displacements of the dam crest before and after reversing the motion produce a larger difference than that using a single component.More importantly,the difference of horizontal displacements of the dam crest caused by polarity reversal of near-fault ground motions increases with the increase of earthquake intensity.Due to the randomness and uncertainties of earthquakes,using a stochastic near-field motion input as excitation without considering the polarity(i.e.,positive vs reversed waveform),does not necessarily obtain a conservative result.展开更多
Earthquakes can affect large dam projects in many different ways.Usually,design engineers are focussing on ground shaking and neglect the other aspects.The May 12,2008 Wenchuan earthquake has damaged 1803 dams and res...Earthquakes can affect large dam projects in many different ways.Usually,design engineers are focussing on ground shaking and neglect the other aspects.The May 12,2008 Wenchuan earthquake has damaged 1803 dams and reservoirs,and 403 hydropower plants with an installed capacity of 3.3GW.Among these dams were the 132-m-high Shapai RCC arch dam and the 156-m-high Zipingpu concrete face rockfill dam.These recently completed dams are dam types which,up to now,have not experienced strong ground shaking.The widespread mass movements have caused substantial damage to dams and surface powerhouses in Sichuan.The different features of earthquake hazard are presented,i.e.,ground shaking,faulting and mass movements.It is proposed to prepare project-specific safety plans for all dams,which consist of a matrix where the possible hazards and the corresponding countermeasures are listed.The earthquake behaviors of the Sefid Rud,Zipingpu and Shapai dams,which,in the past,have experienced strong ground shaking from nearby earthquakes,are discussed.Finally,the need for strong motion instrumentation of large dams is discussed.It is proposed that major dams with large damage potential,dams located in areas of high seismicity,and dams showing signs of abnormal behavior be equipped with strong motion instruments.展开更多
基金National Natural Science Foundation of China under Grant Nos.U1965206,51779034Technology Project of China Huaneng Group Under Grant No.HNKJ18-H25。
文摘In China,an increasing number of high concrete face rockfill dams(CFRDs)are located in high intensity earthquake zones,some of which are close to the seismic fault line.Recordings suggest that near-fault ground motions are characterized by large one-sided velocity pulses.The conventional dynamic analysis of dams,however,neglects the features of strong ground movements.In this study,under different ground motion levels some numerical dynamic studies considering the one-sided broadband pulses of near-fault earthquakes are presented for CFRDs based on a generalized plasticity model for rockfill materials.The results indicate that the displacements of dam crest corresponding to positive and reverse input of near-fault ground motion make a significant difference,while the displacements of the dam crest under artificial seismic waves are similar.Furthermore,using the horizontal and vertical components as simultaneous excitations near the faults,the displacements of the dam crest before and after reversing the motion produce a larger difference than that using a single component.More importantly,the difference of horizontal displacements of the dam crest caused by polarity reversal of near-fault ground motions increases with the increase of earthquake intensity.Due to the randomness and uncertainties of earthquakes,using a stochastic near-field motion input as excitation without considering the polarity(i.e.,positive vs reversed waveform),does not necessarily obtain a conservative result.
文摘Earthquakes can affect large dam projects in many different ways.Usually,design engineers are focussing on ground shaking and neglect the other aspects.The May 12,2008 Wenchuan earthquake has damaged 1803 dams and reservoirs,and 403 hydropower plants with an installed capacity of 3.3GW.Among these dams were the 132-m-high Shapai RCC arch dam and the 156-m-high Zipingpu concrete face rockfill dam.These recently completed dams are dam types which,up to now,have not experienced strong ground shaking.The widespread mass movements have caused substantial damage to dams and surface powerhouses in Sichuan.The different features of earthquake hazard are presented,i.e.,ground shaking,faulting and mass movements.It is proposed to prepare project-specific safety plans for all dams,which consist of a matrix where the possible hazards and the corresponding countermeasures are listed.The earthquake behaviors of the Sefid Rud,Zipingpu and Shapai dams,which,in the past,have experienced strong ground shaking from nearby earthquakes,are discussed.Finally,the need for strong motion instrumentation of large dams is discussed.It is proposed that major dams with large damage potential,dams located in areas of high seismicity,and dams showing signs of abnormal behavior be equipped with strong motion instruments.
