地震作用下黄土边坡动力响应的时频特征分析

地震作用下黄土边坡的动力响应特征与变形失稳机制是具有重要理论与实践意义的课题，但从动力响应频谱特性方面开展的研究还相对较少。以大型振动台模型试验获得的黄土边坡地震动峰值加速度数据为基础，通过分析其变化规律，着重从频谱特性的角度分析，讨论黄土边坡的动力失稳机制。进一步通过对坡面不同高程测点、边坡内部垂直方向以及水平方向上测点的加速度时程进行绝对加速度反应谱分析，从频谱变化角度提出黄土边坡的动力失稳机制。研究表明，黄土边坡在地震动作用下的响应过程可以分为三个阶段：弹性阶段、塑性阶段与破坏阶段；黄土边坡进入破坏阶段时均会伴随反应谱峰值的增幅或者主周期的变化，在弹性阶段反应谱加速度峰值增幅与输入地震动幅值增幅一致，进入塑性阶段后反应谱峰值增幅比输入地震动幅值增幅小；研究提出将反应谱首峰的凸显情况作为坡体破坏程度的判断依据之一。

Time-frequency characteristics of dynamic responses of loess slopes under earthquake action

Research on the dynamic response characteristics and deformation and instability mechanism of loess slopes under earthquake action has important theoretical and practical significance. However, relatively few studies on this topic have been conducted from the perspective of dynamic response spectrum characteristics. The peak ground acceleration data of a loess slope obtained from large-scale shaking table model tests were used in this paper. First, the dynamic instability mechanism of the loess slope was discussed by analyzing its variation law, especially from the perspective of its frequency spectrum characteristics. Then, the analysis of the absolute acceleration response spectrum was performed on the acceleration time histories of measuring points at different elevations of the slope and the points at the vertical and horizontal directions inside the slope. Finally, the dynamic instability mechanism of the loess slope was proposed from the perspective of frequency spectrum changes. Results show that the response process of loess slope under dynamic seismic action can be divided into three stages: elastic stage, plastic stage, and failure stage. When the loess slope enters the failure stage, it is accompanied by an increase in the peak value of the response spectrum or the change of the dominant period. In the elastic phase, the increase in the peak acceleration of the response spectrum is consistent with that of the input ground motion amplitude; in the plastic stage, the increase in the peak acceleration of the response spectrum is smaller than that of the input ground motion amplitude. This study suggests that the highlight of the first peak of the response spectrum can be used as one of the bases for judging the damage degree of the slope.