为研究开挖对黏性土地基中柔性桩筏基础承载的影响,提出一种开挖条件下非均质黏性土地基中柔性桩筏基础非线性分析方法。采用有限元法对筏板进行分析。在考虑桩周土体开挖卸荷影响的基础上,基于荷载传递法,得出了开挖条件下非均质黏性土地基中基桩顶面柔度系数;基于层状弹性半空间理论,对开挖条件下非均质黏性土地基中桩土体系相互作用进行了分析;建立了开挖条件下非均质黏性土地基中桩土体系的柔度矩阵。采用有限元和有限差分相结合的方法得到了开挖条件下非均质黏性土地基柔性桩筏基础非线性简化分析方法。通过与已有试验和理论分析结果进行对比,验证了简化方法的正确性。计算结果表明:忽略开挖卸荷的影响,将低估开挖条件下桩筏基础中土体承担荷载的比例,并使得分析结果中筏板底部基桩桩顶荷载分布的不均匀性偏大。研究成果可为开挖条件下群桩基础和桩筏基础变刚度调平设计提供依据。
Abstract
A simplified nonlinear approach for analyzing flexible piled raft foundation in non-homogeneous cohesive soil under excavation is proposed to investigate the influence of excavation on the bearing capacity of the foundation. The flexible piled raft is modeled as a thin plate through the finite element discretization. With the impact of soil excavation around the pile into consideration, the flexibility coefficient of pile top in non-homogeneous cohesive soil under excavation is obtained by employing the load transfer method; based on solutions for the stress and displacement in layered elastic half space, the interactions of the pile group-soil system are taken into account to determine the flexibility matrix of the pile group-soil system in non-homogeneous cohesive soil under excavation. By integrating finite element method and finite difference method, the simplified nonlinear analysis method is obtained. Comparison between calculated results and test and theoretical results verified the validity of the present method. With the influence of soil excavation ignored, the load sharing ratio of soil in piled raft foundation will be underestimated, and the non-uniformity of load distribution at the top of foundation pile at the bottom of raft will be larger in the analysis results. The research results offer a basis for balance design for variable-rigidity of group piled foundation and piled raft foundation under excavation.
关键词
桩筏基础 /
非线性分析 /
土体卸荷回弹 /
非均质地基 /
基坑开挖
Key words
piled raft foundations /
nonlinear analysis /
unloading rebound of soil /
non-homogeneous foundation /
pit excavation
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基金
国家自然科学基金项目(51608548);河南省高等学校青年骨干教师培养计划项目(2018GGJS106)
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