董建华, 裴美娟. 消除负摩阻力扩体挤密桩的研制及力学特性分析[J]. 工程力学, 2021, 38(5): 72-87. DOI: 10.6052/j.issn.1000-4750.2020.01.0042
引用本文: 董建华, 裴美娟. 消除负摩阻力扩体挤密桩的研制及力学特性分析[J]. 工程力学, 2021, 38(5): 72-87. DOI: 10.6052/j.issn.1000-4750.2020.01.0042
DONG Jian-hua, PEI Mei-juan. DEVELOPMENT AND MECHANICAL PROPERTY ANALYSES OF EXPANDED COMPACTION PILES FOR ELIMINATING NEGATIVE FRICTION[J]. Engineering Mechanics, 2021, 38(5): 72-87. DOI: 10.6052/j.issn.1000-4750.2020.01.0042
Citation: DONG Jian-hua, PEI Mei-juan. DEVELOPMENT AND MECHANICAL PROPERTY ANALYSES OF EXPANDED COMPACTION PILES FOR ELIMINATING NEGATIVE FRICTION[J]. Engineering Mechanics, 2021, 38(5): 72-87. DOI: 10.6052/j.issn.1000-4750.2020.01.0042

消除负摩阻力扩体挤密桩的研制及力学特性分析

DEVELOPMENT AND MECHANICAL PROPERTY ANALYSES OF EXPANDED COMPACTION PILES FOR ELIMINATING NEGATIVE FRICTION

  • 摘要: 针对湿陷性黄土地区等不良土质地区的桩基负摩阻力问题,提出一种既可以消除负摩阻力,又能提高承载力的扩体挤密新型桩,对其结构构成和工作机理进行详细阐述。根据扩体挤密桩的结构特性,建立扩体装置扩张的菱形孔扩张模型,采用复变函数方法,求解了扩体装置扩张的弹塑性解及极限扩张角,推导出该新型桩的单桩极限承载力计算公式。结合算例采用有限元法和提出的理论计算方法对该新型桩的挤土效应和承载特性进行了分析。结果表明:扩体装置对土体应力的影响范围约为扩体装置扩开宽度的2倍~3倍;扩体装置扩张形成的塑性区范围大小在竖直方向上和水平方向上基本相等;各扩体装置承力时具有一定的顺序效应和时间效应,扩体装置的承力能力与周围土体的性质有关;数值模拟结果与理论计算结果基本一致,验证了理论分析方法的正确性;与普通直桩及套管桩相比,扩体挤密桩消除负摩阻力效果良好,提高承载力作用显著,受力机制科学合理,为湿陷性黄土地区桩基工程的设计提供一定的理论依据和参考。

     

    Abstract: To eliminate negative friction on piles in areas of poor soil such as collapsible loess, a new compaction pile with expanders which can eliminate negative friction and improve bearing capacity is proposed. Its structural composition and working mechanism are discussed in detail. According to the structural characteristics of the new pile, a diamond hole expansion model for the expanders is established. The expansion elastic-plastic solution of the expanders and the ultimate expansion angle are solved by the method of complex variable function. Then the calculation formula of the ultimate bearing capacity of the new pile is obtained. The compaction effect and bearing characteristics of the new pile are analyzed by the finite element method and the proposed theoretical method. The results show that: The influence range of the expanders on soil stress is approximately 2 to 3 times the expansion width of the expanders, and the plastic zones formed by expansion are equal in vertical and horizontal directions; There are some order effect and time effect for each expander in load-bearing process, and the bearing capacity of a expander is related to the properties of surrounding soil; The numerical simulation results are basically consistent with the theoretical results, which verifies the correctness of the theoretical analysis method in the paper; Compared with ordinary straight piles and tube piles, the negative friction on the new pile can be well eliminated, the bearing capacity can be obviously improved, and the force mechanism is reasonable. The study provides theoretical basis and reference for the design of pile foundation in collapsible loess areas.

     

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