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铁道科学与工程学报

JOURNAL OF RAILWAY SCIENCE AND ENGINEERING

第12卷    第5期    总第68期    2015年10月

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文章编号:1672-7029(2015)05-1032-07
考虑侧阻增强效应的基桩极限承载力解析算法
杨明辉,李军,赵明华

(湖南大学土木工程学院,湖南长沙 410082)

摘 要: 常规基桩竖向极限承载力计算方法难以考虑由于端阻力提高而引起的侧阻增强效应。分析基桩侧阻增强效应的形成机理,在此基础上,采用Meyerhof对数螺旋线破坏模式模拟桩端土体破坏状态,并引进极限上限理论分析桩端与桩侧土体在极限承载情况下的能量传递规律,利用虚功原理导出桩侧土体对桩身增加的法向压力值,由此根据摩尔库伦理论提出了考虑侧阻增强效应的基桩竖向极限承载力公式。与现场基桩承载力试验数据的对比表明,桩基规范常规算法明显低估了基桩的极限承载力,而本文推算的理论公式则更接近于实测静载荷试验值,表明考虑侧阻增强效应后可更合理评估基桩承载能力。对影响基桩侧阻增强效应的各主要因素进行了探讨,分析结果表明,随桩端土体强度或桩径的增加,侧阻增强效应作用愈明显,该结论对基桩工程设计具有一定的借鉴意义。

 

关键字: 桩基础;侧阻增强;强化效应;极限上限法;极限承载力

Analytical method of ultimate bearing capacity of pile considering enhancement effect in lateral resistance
YANG Minghui,LI Jun, ZHAO Minghua

College of Civil Engineering, Hunan University, Changsha 410082, China

Abstract:Shaft resistance enhancement effect of pile due to the increasing of tip resistance is hard to be considered in conventional method of vertical bearing capacity. Firstly, the mechanism of shaft resistance enhancement effect is analyzed deeply in the paper. On this basis, logarithmic spiral line of Meyerhof is adopted to simulate the failure modes of soil below pile tips, and upper-bound method of limit analysis is introduced to analyze the energy transfer laws of soil below and around piles. Therefore, the incremental normal stress along pile is deduced with the principle of virtual work. The ultimate axial bearing capacity of pile is also obtained by taking the shaft resistance enhancement effect into consideration via Mohr-Coulomb theory. Comparison of calculated values to field data shows that the present method was more reasonable in predicting bearing capacity of pile, and the conventional method underestimates the bearing capacity of pile. Finally, several key parameters relating to shaft resistance enhancement effect are analyzed, and the result shows that shaft resistance enhancement effect would be even more obvious with the increase of soil strength under pile tip and pile diameter. This conclusion could provide a reference to engineering practice.

 

Key words: pile foundation; shaft resistance enhancement;enhancement effect; upper bound limit method; ultimate bearing capacity

ISSN 1672-7029
CN 43-1423/U

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