山区杆塔变径微型桩基础上拔承载特征研究

The study on the uplift bearing characteristics of variable diameter micro pile foundation for mountain transmission towers

摘要

【目的】由于深切峡谷区条件复杂，电网工程小直径配置的杆塔微型桩基础抗拔承载力不足，将传统微型桩与变径桩结合的变径微型桩可能是提高其抗拔承载能力的有效选择，其目的为提高抗拔阻力，具有更高的抗拔性能和更高的成本效益。【方法】进行了5组室内模型试验，对比研究了粉土质砂中传统微型桩与变径微型桩的单桩与群桩的承载特征差异，分析了变径布置与变径微型桩承载机理的关系，并进一步采取数值模拟揭示了多种变径结构参数和地基土体参数对变径微型桩竖向承载力的影响规律。【结果】结果表明，变径微型桩的承载力及材料利用率超过普通微型桩的2倍，其极限荷载下的位移显著大于传统微型桩。此外，变径微型群桩的群桩效应得到增强，且在上拔荷载作用下，桩身各部分承担荷载的方式不同，扩大头的作用逐步显现，承担荷载比超过50%。【结论】不同的变径结构参数对桩基竖向承载力的影响随扩大头与侧摩阻力的变化而变化。考虑施工应用，应合理优化设计结构参数，变径微型桩在高强度地基土处理中表现出更大的优势。

Abstract

[Objective] Due to the complex conditions in deep canyon areas, the pullout capacity of micro-pile foundations configured with small-diameter towers in power grid projects is insufficient. The use of tapered micro-piles, which combine traditional micro-piles with varying diameters, may be an effective solution to enhance pullout resistance. This approach aims to improve the pullout performance while offering greater cost-effectiveness. [Methods] Five groups of indoor model tests were conduceted to comparatively analyze the load-bearing characteristics of traditional micro-piles and tapered micro-piles in sandy silt. It also examined the relationship between tapered arrangements and the load-bearing mechanisms of tapered micro-piles. Furthermore, numerical simulations were employed to reveal how various structural parameters of the tapered design and soil properties affect the vertical load capacity of tapered micro-piles. [Results] The result indicated that the load capacity and material efficiency of tapered micro-piles exceed those of conventional micro-piles by over two times, with displacements under ultimate loads significantly greater than those of traditional micro-piles. Additionally, the group effect of tapered micro-pile groups was enhanced, and under uplift loads, different parts of the pile experienced varying load distributions, with the role of enlarged heads becoming increasingly prominent, carrying more than 50% of the load. [Conclusion] The influence of different tapered structural parameters on the vertical load capacity of the pile foundation varied with changes in the enlarged head and side friction resistance. For practical applications, it is essential to optimize the design parameters rationally, as tapered micro-piles demonstrate greater advantages in the treatment of high-strength foundation soils.

关键词

荷载承担比 / 变径微型桩 / 模型试验 / 数值模拟 / 扩大头 / 桩侧摩阻力

Key words

load sharing ratio / variable diameter micropiles / model tests / numerical simulations / enlarged head / side friction resistance of piles

基金资助

国家电网有限公司科技项目(5108-20221 8280A-2-322-XG)

国家自然科学基金(U23A20651)