散体材料桩复合地基桩土应力比分析

散体材料桩复合地基桩土应力比分析

第38卷第3期 2007年6月 中南大学学报(自然科学版) Vol.38 No.3 J. Cent. South Univ. (Science and Technology) Jun. 2007

散体材料桩复合地基桩土应力比分析

赵明华，张 玲，刘敦平

(湖南大学 岩土工程研究所，湖南 长沙，410082)

摘 要：对散体材料桩复合地基承载力机理及影响桩土应力比的主要因素进行分析与探讨；针对散体材料桩受荷时不仅产生竖向固结，而且伴有侧向鼓胀这一变形特性，基于弹性理论解析，导出线弹性状态下桩体及桩周土的应力 应变关系，进而得出正方形布桩和梅花形布桩这2种典型布桩方式下桩土应力比的计算公式，并在此基础上，分别对桩体和桩间土体进行时效分析；基于弹性理论及太沙基一维固结理论，导出考虑时间效应的桩土应力比计算公式。采用所提出的计算方法对某工程实测结果进行分析与比较，其结果表明，考虑时效后桩土应力比随时间的增加而逐步提高，且理论的桩土应力比变化曲线与实测曲线较吻合。 关键词：散体材料桩；复合地基；桩土应力比；侧向鼓胀；时效

中图分类号：TU473.1 文献标识码：A 文章编号：1672-7207(2007)03 0555 06

Bearing capacity calculating method of

discrete material pile composite foundation

ZHAO Ming-hua, ZHANG Ling, LIU Dun-ping

(Geotechnical Engineering Institute, Hunan University, Changsha 410082, China)

Abstract：The bearing capacity of discrete material pile composite foundation and the main influencing factors of pile-soil stress ratio were discussed, respectively. Based on elastic theory analytic solution, a new calculating method for stress concentration ratio was presented, which was directed towards the deformation performance, that is, the discrete material pile not only had a vertical deformation but also had a lateral deformation under the vertical upper loads. This method can consider both the lateral deformation of discrete material pile under the vertical load and the influence of pile’s arrangement. In addition, the aging effect of both discrete material pile and surrounding soil were analyzed. Based on the elastic theory and Terzzaghi’s one dimension consolidation theory, a modificatory method for stress concentration ratio which took the aging effect into account was proposed. Lastly, a model experiment was analyzed to validate the method proposed. The result shows that the calculated curve agrees well with the measured one.

Key words：discrete material pile; composite foundation; stress concentration ratio; lateral deformation; aging effect

近年来，以碎石桩为典型代表的散体材料桩复合地基在软土地基处理工程中应用广泛，其理论研究也桩土应力比是反映复合地基工得到了很大的发展[1 3]。

作性质的一个重要设计参数，其定义为作用在桩体上的载荷密度与桩间土体上的荷载密度之比。然而，准确确定桩土应力比非常困难，不少学者结合具体的地

收稿日期：2006 10 11

基金项目：国家“863”计划项目(2006AA11Z104)

作者简介：赵明华(1956 )，男，湖南邵阳人，教授，博士生导师，从事桩基础及特殊土地基处理方面的研究 通讯作者：赵明华，男，教授；电话：0731-8821590 (O)；E-mail：mhzhaohd@

基处理形式以及各自的假定条件提出一系列桩土应力比计算公式，如传统的Rowe公式、Baumann公式、Priebe公式、模量比公式以及基于复合地基和天然地基载荷试验Q s曲线推算等方法[4]。模量比公式是其中最简单的方法，它假定在刚性基础下，桩体和桩间土的竖向应变、径向应变相等，但这些假定与实际情