水泥土桩复合地基场地地震效应分析

将复合地基加固区视为均质体,采用课题组提出的基于Davidenkov骨架曲线的土体动弹塑性模型描述复合地基加固区和非加固区土体的动应力-应变关系,基于大型有限元软件ABAQUS的操作平台,开发了土体动粘弹塑性模型的子程序。选择南京某典型软弱场地为研究对象,采用ABAQUS软件进行了复合地基二维弹塑性地震反应分析,研究了输入地震动强度和频谱特性、水泥土桩加固宽度和深度、复合地基模量对复合地基场地地震效应的影响。结果表明:输入地震动强度和频谱特性对复合地基地震效应影响较大;复合地基加固区地表的峰值加速度反应较自由场的反应明显减小,而加固体区外侧地表的峰值加速度反应较之自由场的反应可能增大;复合地基地表的峰值加速度反应随着水泥土桩加固深度和复合模量的增加而减小,而与加固宽度无关。

Site Seismic Response Analysis of Composite Foundation Mixed with Cement Piles

In this paper, the composite foundation is regarded as homogeneous and the dynamic elastic-plastic soil constitutive model, Davidenkov, is used to describe the dynamic stress-strain relationship of the soil and the composite soil. On the basis of the finite element method software package, ABAQUS, the subroutine of dynamic elastic-plastic soil constitutive model is developed. A representative soft site in Nanjing is selected, and a detailed 2D elastic-plastic seismic response of composite foundation is performed with ABAQUS. A few factors such as the frequency characteristics, acceleration peak value of the input ground motion, the depth and width of composite foundation and the composite module that affect the seismic response of composite foundation are considered. Then some rules are presented:the frequency characteristics and acceleration peak value of the input ground motion have great influence on the seismic response of composite foundation. Contrast with the free site′s, the peak acceleration response on the ground surface of the composite foundation is much smaller. But outside the composite foundation, the peak acceleration response on the ground surface may larger than the free site′s. With the depth of the composite foundation increasing, the peak acceleration response on the composite foundation decreases, and so does the composite module. There seem to be no relationship between the width of composite foundation and the peak acceleration response on the ground surface of composite foundation.