饱和黏性土中散体桩复合地基极限承载力系数研究

doi:10.11779/CJGE201503001

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摘要埋置深度对复合地基承载力的影响规律一直缺乏深入研究,工程中采取最低程度考虑基础埋深的保守方法导致复合地基承载力被不同程度的低估。采用有限差分法建立饱和黏土中散体桩复合地基数值模型,对刚性基础下散体桩变形模式及机理进行分析,在此基础上,进行考虑桩、土为无重介质的散体桩复合地基极限承载力系数研究。结果表明散体桩复合地基破坏模式受置换率、桩长和埋深耦合作用,可能发生浅基础型、复合型或实体基础类型的破坏模式。深度修正系数随着桩长的增加而增大,随埋深的增加而减小;当桩长和埋深一定时,存在一个最优置换率使深度修正系数取得极大值。而现行规范中深度修正系数取1.0,低估了基础埋深的作用。最后基于Mohr-Coulomb破坏准则推导群桩复合地基的等效强度,并利用极限分析法推导了浅基础破坏模式下复合地基的极限承载力系数解答,结果与有限差分法的结果吻合较好。

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关键词 ：复合地基, 深度修正系数, 有限差分法, 极限分析, 破坏模式

Abstract：The effect of the embedded depth of composite ground on its bearing capacity has not been investigated deeply. The bearing capacity of composite ground is underestimated due to the conservative value of embedded depth considered in engineering practice. A finite difference model is established to study the failure mechanism of granular column under rigid foundation and the ultimate bearing capacity factors of granular column-reinforced composite ground without weight. The results indicate that the potential failure modes of granular column-reinforced composite ground can be categorized into shallow foundation failure, composite failure and block foundation failure, depending on the replacement ratio, length of piles and embedded depth. The depth correction factor increases with the length of columns and decreases with the embedded depth. When the length of column and the embedded depth of foundation keep constant, there is an optimum value of replacement ratio to obtain the maximum value of depth correction factor. According to the calculated results, the effect of embedded depth is underestimated by depth correction factor of 1.0 in the existing code. Based on the Mohr-Coulomb yield criterion, a formula for the equivalent strength method of composite ground is deduced and the bearing capacity factor of the shallow failure mode is evaluated by the limit analysis method, which agrees well with the results of finite difference method.

Key words： composite ground depth correction factor finite difference method limit analysis method failure mode

收稿日期: 2014-06-04

TU44

基金资助:国家自然科学基金项目（51378345）

作者简介: 郑刚(1967- ),男,教授,博士生导师,从事土力学及岩土工程教学与科研工作。E-mail: zhenggang1967@163.com。

引用本文:

郑刚, 周海祚, 刁钰, 刘景锦. 饱和黏性土中散体桩复合地基极限承载力系数研究[J]. 岩土工程学报, 2015, 37(3): 385-399. ZHENG Gang, ZHOU Hai-zuo, DIAO Yu, LIU Jing-jin. Bearing capacity factor for granular column-reinforced composite ground in saturated soft clay. Chinese J. Geot. Eng., 2015, 37(3): 385-399.

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