凹陷地形地震波加速度放大效应的振动台模型试验研究

设计并完成了1:10的大比例尺高山河谷地形的非均质场地大型振动台模型试验，研究了El Centro和汶川卧龙地震波在三向激振作用下凹陷地形内顺坡向、垂直坡向和底部场地的加速度动力响应规律。结果表明:①顺坡向和垂直坡向的X，Y，Z向加速度均具有高程放大效应，且凹陷地形底部的放大性最小；②凹地底部X，Y，Z向的加速度及其反应谱峰值均具有高程放大效应，底面两侧的加速度存在较大的差异，具有明显的软土放大效应；③顺坡向时0.4 g地震波作用下加速度反应谱峰值的放大性大于0.2 g时，0.1 g最小；对于汶川地震波来讲，凹地底部的加速度反应谱的放大性最小，El Centro地震波时，则是距离坡脚3/4处的加速度反应谱的放大性最小；垂直坡向的加速度反应谱峰值的放大性在凹地底部最小；④凹地底部X，Y，Z向的加速度傅里叶谱变化情况基本一致，地震波由底部向沟谷内部传播时，加速度傅里叶谱的低频成分逐渐增大而高频成分减弱。

Experimental Study on Shaking Table Model for Acceleration Amplification Effect of Basin Seismic Wave

A large-scale shaking table model test of an alpine valley topography nonhomogeneous ground with the geometric scale of 1:10 was performed to study the dynamic response characteristics of seismic acceleration including the directions of perpendicular and along the trend of slope and basin floor under EL centro wave and Wenchuan Wolong seismic wave with three excitation directions. The results show that the accelerations of the directions of X,Y and Z along the trend of slope and its perpendicular orientation have elevation amplification effect, and the impact of basin floor is minimum; the accelerations and its response spectrum peak of the directions of X,Y and Z on the basin floor also have elevation amplification effect, and the accelerations at both sides of the basin bottom have large difference and have obvious soft soil amplification effect; along the orientation of slope, the amplification of acceleration response spectrum peak with the 0.4 g seismic excitation is maximum and when the seismic excitation is 0.1 g, it is minimum. The amplification of acceleration response spectrum is minimum on the bottom of basin for Wenchuan seismic wave, however, for EL centro seismic wave, it is minimum on the place which 3/4 distance away from the slope toe; and the amplification at perpendicular direction is minimum at the bottom of basin; the variations about acceleration Fourier spectrum of the directions of X,Y and Z on the bottom of basin are basically the same, and when the seismic wave transmits from the bottom to the inside of basin, the low-frequency components of acceleration Fourier spectrum will gradually increase, on the contrary, the high-frequency components decrease.