冻土地区钻孔灌注螺纹桩竖向承载特性分析

Numerical analysis of vertical bearing capacity of bored screw pile in permafrost region

  • 摘要: 多年冻土地区钻孔灌注螺纹桩是一种新型桩型,研究其竖向承载特性,对其推广应用具有重要价值。利用室内模型试验验证数值方法,通过数值模拟研究其承载力组成模式,并与广泛使用的普通钻孔灌注桩比较,最后提出多年冻土区钻孔灌注螺纹桩单桩承载力估算方法。研究表明:多年冻土地区钻孔灌注螺纹桩90%承载力来源于桩侧混凝土与冻土的机械咬合作用,多年冻土的抗剪强度决定桩基承载力,季节活动层对其承载力影响很小,桩体承载力全年稳定。多年冻土地区钻孔灌注螺纹桩桩侧螺纹与土体咬合,通过轴力计算的等效摩阻力远大于常规灌注桩与冻土间的冻结力。多年冻土地区钻孔灌注螺纹桩达到极限承载力后桩侧塑性区连通,桩周土体剪切破坏,使用改进公式计算单桩竖向承载力在工程实践中可有效估算单桩承载力设计值。

     

    Abstract: Bored screw pile in permafrost region is a new type of pile, and its vertical bearing characteristics have a great value for its popularization and application. The numerical method is verified based on indoor model test, and its bearing capacity composition mode is studied by numerical simulation, and compared with the widely used common bored pile. Finally, the estimation method of single-pile bearing capacity of the bored screw pile in permafrost region is put forward. The research shows that 90% of the bearing capacity of the bored screw pile in permafrost region comes from the mechanical occlusion between pile side concrete and permafrost, the shear strength of permafrost determines the bearing capacity of pile foundation, and the seasonal active layer has little influence on its bearing capacity, so the bearing capacity of pile body is stable all the year round. In permafrost regions, the equivalent friction calculated by axial force is far greater than the freezing force between conventional cast-in-place pile and frozen soil when the side threads of bored cast-in-place pile occlude with soil. When the pile reaches the ultimate bearing capacity, the plastic zone of the pile side is connected, and the soil around the pile is shearing. It can effectively estimate the design value of the bearing capacity of a single pile in engineering practice by improved formula to calculate the vertical bearing capacity of a single pile.

     

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