风干堆积体边坡地震响应的动力离心模型试验

 堆积体边坡在我国西南地区广泛分布，为深入研究其地震响应规律，设计完成了1∶50比尺的概化边坡离心振动台模型试验，分析4级不同强度地震连续作用下，风干堆积体边坡的加速度响应、边坡变形及其失稳模式。试验结果表明，堆积体边坡水平向PGA放大系数表现出了典型的高程放大效应与趋表放大效应。沿堆积体边坡高程方向，输入地震波频谱特性发生了明显改变，各测点加速度傅里叶谱的卓越频率随PGA增大而降低。考虑竖直向加速度放大效应的影响后，发现合放大系数与水平向夹角随高程有减小的趋势，反映了坡面处发生的波场分裂与波型转换现象。随地震波幅值的增大，水平向与竖直向PGA放大系数均先减小后增大。试验过程中观察发现在地震波加速度峰值达到0.216 g时堆积体边坡开始失稳，坡顶沉降明显，失稳模式以浅层崩滑为主。

Dynamic centrifuge tests on seismic responses of air-dried deposit slopes

In order to study the seismic behaviour of deposit slopes which distribute widely in south-west of China，a generalized model of deposit slopes was designed for the dynamic centrifuge tests with the geometric scale of 1∶50. In this paper，the influence of the amplitude of input earthquake excitations on the dynamic response of a air-dried deposit slope was studied in the 4-stage centrifuge tests and the effect of earthquake acceleration amplification，the deformation mode and the failure pattern of the slope model were analysed. The test results indicated that the horizontal amplification coefficients of peak ground acceleration(PGA) reached the maximum values at the crest，reflecting the amplification effect of altitude. The Fourier spectrum characteristics of input seismic wave were certainly changed along the height. The predominant frequencies corresponding to the Fourier spectrum peak at each measuring point on slope surface decreased with the increasing of PGA. Considering the influence of vertical acceleration amplification，the angle between the direction of the resultant amplification coefficient and the horizontal direction decreased with the increase of the slope elevation，which reveals the phenomena of wave field splitting and waveform conversion. In addition，both the horizontal and vertical amplification coefficients of PGA decreased first then increased considerably as the input acceleration amplitude increased. The failure of deposit slope in the dynamic centrifuge testing was observed to start when the input acceleration increased to 0.216 g. The residual displacements at the crest were obvious and the failure surface appeared to be fairly shallow.