竖向荷载下群桩承载特性的弹塑性分析

Elastico-plastic analysis on load-bearing characteristics of pile groups under vertical loads

分别采用Lade Duncan模型和刚 塑性薄单元模型模拟土体的弹塑性和桩土界面的相对运动 ,对竖向受荷群桩进行了三维弹塑性有限元分析。研究表明 :大、小桩距群桩的承载性状有明显差异 ,大桩距群桩侧摩阻力存在“沉降软化”现象 ,不同于小桩距群桩的“沉降硬化” ;增大桩距有利于调动台底土参与工作 ,提高承台分担比 ;随荷载增大 。

D elastico plastic finite element method was used to analyse the behavior of vertically loaded pile groups by using Lade Duncan model and stiff plastic thin unit model respectively,to simulate elastico plastic soil body and the relative movement between piles and the surrounding soil.The analytic results showed that the obvious differences of the load bearing characteristics of pile groups exist for large or small pile spacings,i.e.,the surrounding friction resistance of pile group with large pile spacing occurs “settling softening” phenomenon,which is different from “settling hardening” of those with small pile spacing; To increase pile spacing is benificial to transferring load to soil under the supporting platform and thus can increase the ratio of platform′s load to total load;With the increase of load,the differences of reaction on pile tops decrease,and the distribution of total load on group piles trends towards approximately uniform.