成层软土中局部开孔透水管桩承载力时变分析理论

    Time-Dependent Analysis of Bearing Capacity for Permeable Pipe Piles with Localized Openings in Layered Soft Clay

    • 摘要: 针对深厚成层软土地基中透水管桩的承载力时变问题,本文提出了一种基于固结度相关荷载传递法的桩基时变承载力分析理论,揭示了软土中预制桩桩侧摩阻力发挥机理和负摩阻力演变规律。首先基于三维轴对称固结理论推导考虑桩侧排水的地基固结解析解,结合非线性时变荷载传递函数,实现桩-土相互作用的时变模拟。通过与已有模型试验和现场实测数据的对比,验证了本文理论模型的正确性。最后对透水管桩的开孔率、开孔位置及开孔长度进行了参数敏感性分析。研究发现,透水管桩的开孔率是影响地基固结和承载力发挥效率的首要影响因素,随着开孔率的增加,排水效果增强,但当开孔率超2.0‰~2.5‰后收益呈边际递减趋势。此外,合理的局部开孔设计(如覆盖中性点至桩底区域)在保证桩身结构强度的同时,可达到接近全桩长开孔的排水效果。

       

      Abstract: This study develops a theoretical model for predicting the time-dependent bearing capacity of permeable pipe piles in deep layered soft soils, utilizing a consolidation-degree-dependent load-transfer method. It reveals the mechanism of side friction mobilization and the evolution of negative skin friction in precast piles embedded in soft soil. Firstly, an analytical solution for foundation consolidation considering pile side drainage is derived based on the three-dimensional axisymmetric consolidation theory, which is then combined with a nonlinear time-varying load transfer function to simulate the time-varying pile-soil interaction. The validity of the proposed theoretical model was verified through comparisons with existing model tests and field measurement data. Finally, a parametric sensitivity analysis was conducted on the opening rate, opening position and opening length of the permeable pipe pile. The study reveals that the opening rate of the permeable pipe pile is the primary factor affecting the consolidation of the foundation and the efficiency of the bearing capacity. With the increase of the opening rate, the drainage effect is enhanced, but when the opening rate exceeds 2.0‰ ~ 2.5 ‰, the marginal benefit diminishes. Furthermore, reasonable local opening design (such as covering the neutral point to the pile tip) can achieve the drainage effect close to the full pile long opening while ensuring the structural strength of the pile.

       

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