预留土支护基坑旋转破坏模式下极限抗力上限解
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重庆大学 土木工程学院

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中图分类号:

TU432

基金项目:

国家科技攻关计划


Upper bound solution of ultimate resistance of berm-retained excavations under rotating failure mode
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Affiliation:

School of Civil Engineering,Chongqing University

Fund Project:

The National Key Technologies R&D Program of China

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    摘要:

    对于支撑式或锚拉式支挡结构,进行预留土辅助支护时,需验算绕支点的抗倾覆稳定性,目前还未找到合理的计算方法。本文基于极限分析上限定理,提出预留土支护基坑的三种可能破坏模式,运用斜条分法对被动区土体进行离散,并构建相容速度场,分别推导了三种破坏模式下基坑抗倾覆力矩的计算表达式,通过算例,采用自编遗传算法分析了支挡结构与土体间摩擦系数、土体粘聚力及预留土几何参数等对破裂角及抗倾覆力矩的影响规律。结果表明:当墙背光滑且土体粘聚力为零时,利用朗肯被动土压力理论计算得到的抗倾覆力矩为一上限解,存在粘聚力时,朗肯被动土压力理论计算值偏于保守,存在摩擦系数时,本文方法相比库伦土压力理论计算结果与实际情况更加吻合,另外,预留土高度相比预留土宽度和坡度对抗倾覆力矩的影响更加显著。

    Abstract:

    For strutted or anchored retaining structures, the anti-overturning stability around the fulcrum needs to be checked for the berm-retained excavations. A reasonable calculation method has not yet been found. Based on the upper limit theorem of limit analysis, three possible failure modes of the berm-retained excavations are proposed, the slice method with inclined interfaces are used to separate the passive soil area, and a compatible velocity field is constructed. The expressions for calculating the anti-overturning moment of foundation pit under three failure modes are derived respectively. Through the calculation example, the effects of friction coefficient between retaining structure and soil, soil cohesive force and the berm-retained geometric parameters on the rupture Angle and anti-overturning moment were analyzed by using self-compiled genetic algorithm. The results show that when the wall is smooth and the soil cohesion is zero, the anti-overturning moment calculated by Rankine"s passive earth pressure theory is an upper bound solution. When cohesive force exists, the theoretical value of Rankine"s passive earth pressure theory is conservative, when friction coefficient exists, compared with the theoretical calculation results of Coulomb"s earth pressure, the method in this paper is more consistent with the actual situation. In addition, the berm-retained height has a more significant influence on the anti-overturning moment than the berm-retained width and slope.

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  • 收稿日期:2021-06-13
  • 最后修改日期:2021-09-25
  • 录用日期:2021-10-15
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