Nested Newmark model to estimate permanent displacement of seismic slopes with tensile strength cut-off

Abstract

Nested Newmark model(NNM) is a conceptual framework to assessing post-earthquake movements including dispersed shear movements. The original NNM omits that the tensile stresses would be encountered in slopes induced by earthquakes. The purpose of this study is to introduce the tensile strength cut-off and the relevant failure mechanism into NNM and conduct the limit analysis to determine the seismic displacement. Parametric studies are carried out to further investigate the influence of the tensile strength and input ground motions on permanent displacement. Neglecting the tensile strength can underestimate the permanent displacements of slopes. As the peak acceleration increases, the underestimation becomes more significant. With the reduction of tensile strength, much larger deformation occurs next to the slope crest. Although the present results are limited to an example, the method is of value in practice to predict the post-earthquake profile of slope.

摘要

嵌套式Newmark 模型(NNM)是一种考虑土体剪切运动特性的地震边坡变形计算模型, 该模型 无法考虑边坡在地震作用下土体出现拉应力屈服特性。本文将土体拉伸截断特性考虑到了NNM 模型 中, 采用极限分析上限法建立了边坡地震永久位移计算方法。通过对拉伸截断参数与地震参数的敏感 性分析, 发现忽略土体的拉伸截断会低估边坡地震永久位移。随着地震峰值加速度的增大, 拉伸截断 对边坡变形的影响将更加显著; 随着抗拉强度的减小, 地震边坡的最大变形位置逐步向坡顶靠近。