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李绪勇, 杨忠平, 刘纲, 李勇华, 张益铭. 隔离式螺旋桩抗压承载与抗地基冻融特性[J]. 岩土工程学报. DOI: 10.11779/CJGE20230209
引用本文: 李绪勇, 杨忠平, 刘纲, 李勇华, 张益铭. 隔离式螺旋桩抗压承载与抗地基冻融特性[J]. 岩土工程学报. DOI: 10.11779/CJGE20230209
Characteristics of compressive bearing capacity and resistance to foundation freeze-thaw of the isolation helical pile[J]. Chinese Journal of Geotechnical Engineering. DOI: 10.11779/CJGE20230209
Citation: Characteristics of compressive bearing capacity and resistance to foundation freeze-thaw of the isolation helical pile[J]. Chinese Journal of Geotechnical Engineering. DOI: 10.11779/CJGE20230209

隔离式螺旋桩抗压承载与抗地基冻融特性

Characteristics of compressive bearing capacity and resistance to foundation freeze-thaw of the isolation helical pile

  • 摘要: 基于针对竖向承载并消除地基冻融影响需求所设计的隔离式螺旋桩,结合物理模型试验与有限元数值方法,从桩体受力视角对比揭示了两种特征螺旋桩(S/D<S/Dcr与S/D≥S/Dcr)受压沉降时桩身受力演化、荷载传递与地基响应特征,以及桩体几何参数对单桩承载力的影响规律及机理;验证了该新型桩抵抗地基冻融变形性能。结果表明:(1)两种特征桩型底螺旋及以下桩身在受荷沉降过程具有相同受力及演化特征,而其余上部螺旋端阻和螺旋间桩侧摩阻大小及演化特征差异显著;(2)S/D≥S/Dcr桩各螺旋端阻相当,且螺旋对下卧土施加附加应力显著提高了其下桩侧摩阻力,并主导了螺旋间桩侧摩阻自上而下近指数衰减趋势;S/D<S/Dcr桩上部螺旋端阻仅约为1/5底螺旋端阻;(3)两种特征桩型单桩承载力随顶螺旋埋深比、螺旋直径与螺旋数量增长线性提升,随中心桩桩径增长先线性增大后加速衰减,桩型参数对S/D≥S/Dcr桩承载力影响更显著;S/D<S/Dcr桩承载力随S/D增长显著提升,相反S/D≥S/Dcr桩承载力线性衰减;(4)螺旋桩较传统桩具有显著抗地基冻融变形影响优势,在冻土深度内设置隔离套可进一步消除影响。

     

    Abstract: Based on the isolation helical pile designed to resist vertical loads and eliminate the effect of foundation freeze-thaw, the pile force evolution, load transfer, and foundation response characteristics of two typical types of helical piles (S/D<S/Dcr and S/D≥S/Dcr) during settlement, as well as the influences and mechanisms of pile geometries on the bearing capacity of the single pile are revealed from the pile force perspective. Furthermore, the performance of the new pile against foundation freeze-thaw deformation is examined. The results show that: (1) The bottom helixes and the lower pile bodies of the two typical piles share the same stress characteristics during the settlement, whereas the stress magnitude and evolution characteristics of the remaining upper helixes’ end resistances and inter-helixes pile side friction resistances differ significantly. (2) The end resistance of each helix of pile S/D≥S/Dcr is essentially equal, and the additional stress that the helixes exert on the underlying soil significantly enhances the pile side friction. This also determines the top-down near-exponential decay trend of the pile side frictional resistance between the helixes. The upper helixes’ end resistances were only about 1/5 of the bottom one for pile S/D<S/Dcr. (3) The compressive bearing capacities of the two types of piles all grow linearly as embedment ratio, helix diameter, and helix number increase, while linearly increases first and then decreases rapidly with the increment of shaft pile diameter. These pile geometries possess heavier impacts on the bearing capacity of pile S/D≥S/Dcr. The bearing capacity of pile S/D<S/Dcr increases significantly with the increase of S/D, whereas that of pile S/D≥S/Dcr decreases linearly. (4) Helical pile has a significant advantage over the conventional pile in resisting the impact of foundation freezing-thawing deformation. The impact can be further eliminated by installing an isolation sleeve on the pile within the frozen soil depth.

     

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