基于振动台试验的黄土塬边斜坡动力响应特性研究

Research on dynamic response characteristics of loess tableland slopes based on shaking table test

以平凉市崆峒区的黄土塬斜坡为原型,采用含裂隙与不含裂隙的斜坡概念模型,设计并完成1:25的大型振动台试验。在满足相似原理的前提下,通过输入不同幅值的水平向与竖直向地震波,分析两种结构的斜坡动力响应特性。结果表明:水平与竖直向地震波沿着坡面和内部竖直方向上均表现出明显的非线性放大效应,并在坡顶达到最大值;同等幅值的地震波作用下,在坡体中上部,坡面与断面4的加速度放大系数大于同等高程处无裂隙斜坡侧,而在断面1处,含裂隙斜坡的放大系数却小于无裂隙斜坡;输入地震波经斜坡土体传递后,卓越频率发生了显著的变化。随着高程的增加,坡体会对中高频段进行选择性放大作用,在含裂隙斜坡侧这种作用更为明显,且随着地震波的幅值增加,卓越频率向低频方向转移。在竖向地震波作用下,卓越频率衰减现象却不明显。

Based on the typical loess plateau slope of Kongtong district, Pingliang city, a 1:25 large-scale shaking table test is designed and accomplished using the conceptual model of the slopes with or without cracks. On the premise of satisfying the similarity principle, the dynamic response characteristics of model slopes of two kinds of structures are analyzed by inputting seismic waves in horizontal direction and vertical direction with different amplitudes. Results show that the horizontal and vertical seismic waves have obvious nonlinear amplification along the slope surface and the internal vertical direction, which reach the maximum value at the top of the slope. Under the horizontal seismic waves with the same amplitude, the acceleration amplification coefficient of the slope surface and section 4 are greater than that of the slope without crack at the same elevation in the middle and upper part of the slope, while in section 1, the amplification coefficient of the crack slope is smaller than that of the crack-free slope. After the seismic wave propagates through the slope soil, the predominant frequency changes significantly. With the increase of elevation, the slope will manifest selective amplification on middle and high frequency bands, which is more obvious on the side of fissure slope. Moreover, as the amplitude of seismic wave increases, the superior frequency transfers to the low frequency direction. However, the remarkable frequency attenuation is not obvious under the vertical seismic wave.