黄土边坡动力失稳的振动台试验研究

Research on Dynamic Failure of Loess Slope by Shaking Table Test

与傅里叶变换相比,小波包变换能够反映地震波的时域和频域局部化特性,因此,引入小波包分析方法进行地震动响应信号的分析.通过大型振动台试验研究了黄土边坡的动力失稳过程,分析了峰值加速度PGA及加速度放大系数AFA的放大效应,并利用MATLAB编程实现加速度信号的小波包变换.研究表明:PGA和AFA的放大效应与边坡的变形损伤累积息息相关;边坡动力失稳过程中起主要作用的是地震波的低频部分(0.1~12.51 Hz),而且随着边坡的损伤累积,第一频段(0.1~6.25 Hz)的能量占比E1和第二频段(6.26~12.51 Hz)的能量占比E2的高程规律会发生明显变化;研究结果表明,黄土边坡的地震失稳过程可以划分为弹性变形、塑性小变形和大变形失稳三个阶段.

Compared with Fourier transform,wavelet packet transform can reflect the localization characteristics of seismic wave in time domain and frequency domain.Therefore,wavelet packet analysis method is introduced to analyze seismic response signal.The amplification effect of PGA and AFA was analyzed in the course of studying dynamic failure process of loess slope by a large-scale shaking table test,and the method of Wavelet Packet Transform was used to achieve analyzing acceleration signal by MATLAB programming.The research shows:firstly,the amplification effect of PGA and AFA is closely related to the cumulative damage to the slope caused by earthquake.Secondly,the low frequency component(0.1~12.51 Hz)of seismic wave plays a major role in the failure process,and the elevation law of E 1 that represents energy ratio of the first frequency band(0.1~6.25 Hz)and E 2 which means the energy ratio of the second frequency band(0.1~6.25 Hz)will change obviously as the accumulation of damage to slope.The research results indicate that the seismic failure process of loess slope can be divided into three stages:elastic deformation phase,small plastic deformation phase and large deformation failure phase.