多级边坡平台宽度对边坡地震动力响应 及破坏机制的影响

以典型工程边坡为原型，利用FLAC3D有限差分软件建立一个三维土坡模型，分析地震作用下多级边坡平台宽度对边坡动力响应特性和动力失稳机制的影响。计算结果表明，边坡设置平台可以有效地提高地震动力条件下边坡的稳定性，且平台宽度越大则稳定性越显著；PGA放大系数随着平台宽度的增大而减小。结合频谱分析得到第一级边坡坡顶的动力响应较第二级边坡坡脚的大，边坡岩土体剪应变增量和位移响应也减小；地震作用下边坡塑性区从坡脚部位向坡体内部发展，随地震持时的增加，坡顶出现拉张变形，坡面及其浅表层发生拉张剪切变形，坡体内部一定部位发生剪切变形；坡面监测点位移时程曲线表明，地震作用下边坡坡脚位移向上，发生剪出变形或破坏，坡脚和变坡点均为薄弱部位，应加强支护。研究结果对多级土质边坡抗震设计具有一定指导意义。

Study of effect of platform width on dynamic response and failure mechanism of stepped slopes under earthquake

Regarding the typical engineering as the prototype, we utilize the FLAC3D finite difference software to build the model of a three-dimensional slope, and analyze the impact on slope dynamic response characteristics and dynamic instability mechanism which are influenced by stepped slope platform width. The results show that the slope platform can effectively improve the slope stability under seismic dynamic conditions; the slope with greater platform width will be more stable; and the PGA amplification factor decreases with the increase of platform width; moreover, the first step dynamic response of a slope on the top of the hill is more outstanding than the second step toe with the combination of spectrum analysis. The slope’s rock and soil shear strain increment and the displacement response is also reduced. Plastic zone of slope under earthquake develops from the toe area to inner slope increasing with the earthquake duration; at the same time hill will be tensile deformation; slope and shallow surface layer will be tensile shear deformation, and certain parts of the slope will present a shear deformation. Displacement curves of slope monitoring points show that slope toe displacement is upward under earthquake; and the cut deformatiobn will occur; the slope slope toe and the point of gradient change become weak parts; so it should be protected tightly. The results have a guiding significance to the seismic design of earth slopes.