双江口心墙堆石坝地震加速度反应的振动台模型试验研究

Shaking table model tests on seismic acceleration response of Shuangjiangkou high earth-rockfill dam

本文通过不同地震波输入的振动台模型试验,得到模型坝的加速度分布资料,研究测点位置、台面地震波强度、地震波类型、多向输入、先期振动和蓄水等因素对加速度放大倍数分布的影响。研究表明:(1)坝体地震动加速度反应在河谷坝段最为强烈,且随所处坝体部位高度的增加而增强;(2)对相同高程上各点,以中心线坝体测点加速度反应最小,上、下游次之,整个坝体的表面放大效应明显;(3)地震波类型对加速度放大倍数和分布有重要影响,集中体现在地震波卓越频率与坝体自振频率的关系上;(4)随输入地震峰值加速度的增大,坝体各点加速度放大倍数有减小的趋势;(5)垂直方向(z向)地震动有加大顺河水平向(x向)加速度反应的作用,特别是在坝顶表现比较明显;(6)先期振动会引起坝体后续地震动加速度反应的增大;(7)坝体的加速度反应在空库时比满库蓄水时强烈。

Through shaking table model tests,the seismic acceleration response and its influencing factors of the Shuangjiangkou high earth-rockfill dam,including sampling locations,seismic peak ground acceleration,directions of seismic waves,pre-vibrations and reservoir filling,are studied.Results show that：（1） The acceleration is the strongest on the main section of the dam and increases with height;（2） At the same height,the acceleration is the weakest on the dam axis,and it gradually increases upstream-ward or downstream-ward.Surface amplification effect is significant;（3） The type of seismic waves has a great impact on acceleration magnification and its distribution,particularly on the relationship of the dominant frequency of inputted wave versus the dam ＇s natural frequency;（4） Acceleration magnification shows a decreasing trend as the peak ground acceleration increases;（5） Vertical seismic ground vibration causes an increase in stream-wise acceleration,especially at the dam crest;（6） Pre-vibrations intensify the seismic acceleration;（7） Reservoir filling has a considerable impact on seismic acceleration,the response without water is stronger than full of water.