某软土深基坑工程时间效应有限元分析

软土地区的深基坑因土体的固结作用和流变性而具有了时间效应。本文以Biot固结有限元法为基础,用三元件模型中的第一个线性弹簧模拟固结作用,弹性模量考虑了开挖应力路径和应力历史的影响;另外一部分(KELVIN模型)来模拟土体的流变性,以实际变形的反演来得到两个参数的大致取值,再对基坑的变形情况以及进一步开挖进行分析。假定为正常固结饱和粘土,平面应变问题。通过对某饱和软粘土地基深基坑开挖工程实例的分析,得到的挡墙水平位移曲线与实测曲线很吻合,表明程序较好地反映出基坑的时间效应。

FINITE ELEMENT ANALYSIS OF TIME-EFFECT ON DEEP EXCAVATIONS IN SOFT CLAY

In soft clay,because of its consolidation and creep,time effect is detectable in deep excavation.In this paper,finite element method coupled with Biot consolidation theory is used to research the behavior of deep excavation.The first linear spring is used to stimulate the consolidation.The elastic module is considered about the influence of the excavating stress-path and stress-history.The other part of the model(KELVE model) is used to stimulates the creep of clay.Its two parameters are gained approximately through partly analyzing the real deformation in the engineering.Then the deformation associated with whole excavation is analyzed step by step during the process of excavation.Normally-consolidated and saturated clay is assumed,and plane strain problem is considered.When analyzing a real example of deep excavation in saturated soft clay,the curve of the wall horizontal displacement computed is quite inosculated to the field measured ones,so it indicates that this finite element code is good for stimulating time-dependent behaviors of excavation.The reason why there are some curves not-well-inosculated is also explained.The sedimentation rule of post-wall ground surface is provided in addition.