基于振动台试验的黄土场地效应研究

地震作用下黄土场地对地震波不同分量的放大效应影响显著。针对黄土高原典型黄土场地在地震作用下的放大效应，设计并完成大型地震模拟振动台试验，通过输入不同强度的地震动荷载，研究黄土场地加速度（PGA）放大系数、傅里叶谱、加速度反应谱、H/V谱比与地震动强度和场地高度的变化规律，揭示地震波不同分量对黄土场地效应的影响。结果显示：黄土场地对地震波的水平分量具有明显的放大效应，对地震波垂直分量的放大效应影响较小；随着高程的增加，地震波水平分量PGA放大系数呈现非线性变化；随着地震动强度和高程的增加水平分量卓越频率的频段和幅值逐渐增加，卓越频率向低频偏移，放大倍数呈现出非线性特性。

Loess Site Effect Based on Shaking Table Test

Based on the data of a large-scale shaking table test, this study employed the peak ground acceleration (PGA) amplification, Fourier spectrum, acceleration response spectrum, and the H/V spectral ratio to investigate the non-linearity of a loess site effect under strong earthquakes. Then the impacts of different seismic components on the loess site effect were determined. The results showed the following: (1) With the increase in the ground-motion intensity, the PGA amplification coefficient of the horizontal component significantly decreased, while that of the vertical component slightly increased. (2) With the gradual change in vertical monitoring points from the bottom to the surface, the PGA amplification coefficient of the horizontal component of the loess site presented a nonlinear change, while that of the vertical component had no significant change. (3) With the increase in elevation, the predominant frequency band and amplitude of the horizontal component gradually increased, while the Fourier spectrum of the vertical component exhibited no significant change. (4) With the increase in elevation and ground-motion intensity, the horizontal component of the acceleration response spectrum increased. (5) As the ground-motion intensity increased, the low frequency became the predominant frequency, and the amplification factor presented a nonlinear characteristic.