地震作用下非等宽平台路堑边坡的动力响应研究

Study on dynamic response of unequal width platform cutting slope under earthquakes

非等宽平台设计是提高碎裂岩体路堑高边坡动力稳定性的有效方法之一,在规范平台宽度不小于2 m背景下,研究该类型边坡的动力响应特征具有重要工程应用价值。通过FLAC3D有限元软件计算三级台阶式边坡平台位置的PGA放大系数、塑性变形区和最大剪应变,然后基于数值模拟结果设计大型振动台物理模拟试验开展非等宽台阶式边坡变形失稳特征和PGA放大系数变化研究,对二级平台宽度引起的边坡破坏程度进行分析,提出路堑边坡工程设计建议。数值模拟表明,随着中间平台宽度增加PGA放大系数先减后增,考虑平台的分割效应下建议该工程二级平台宽度为4 m;物理试验表明,边坡易在平台处产生应力集中,平台分割效应使边坡逐渐分解为局部破坏,地震作用下发生累进变形破坏,分为缓慢变形、加速变形和失稳破坏阶段。研究成果为该类型路堑边坡平台的设计提供了依据。

The design of unequal width platform is one of the effective methods to improve the dynamic stability of high cutting slope in cataclastic rock mass.Under the background that the width of standard platform should not be less than 2 m,it is of great engineering application value to study the dynamic response characteristics of this type of slope.The PGA amplification factor,plastic deformation zone and the maximum shear strain of the platform position of the three-level stepped slope are calculated by FLAC3D finite element software.Then,based on the numerical simulation results,a large-scale shaking table physical simulation test is designed to carry out the research on the deformation and instability characteristics of the non-equal-width stepped slope and the change of PGA amplification factor.The slope failure degree caused by the width of the two-level platform is analyzed,and the design suggestions of the cutting slope engineering are put forward.The numerical simulation shows that the PGA amplification coefficient decreases first and then increases with the increase of the width of the intermediate platform.Considering the platform segmentation effect,the width of the secondary platform of the project is recommended to be 4 m.The physical test shows that the slope is prone to stress concentration at the platform.The platform segmentation effect causes the slope to gradually decompose into local damage.Progressive deformation and failure occur under earthquake action,which can be divided into slow deformation,accelerated deformation and instability failure stages.The research results provide a basis for the design of this type of cutting slope platform.