基于群桩基础改进的变径微型桩承载特征研究

任光明; 李海涛; 王必杨; 范荣全; 董斌; 罗毅

doi:10.16030/j.cnki.issn.1000-3665.202304050

基于群桩基础改进的变径微型桩承载特征研究

1.
地质灾害防治与地质环境保护国家重点实验室，四川成都　610059

2.
国网四川省电力公司经济技术研究院，四川成都　610041

基金项目: 国家电网公司科技项目（SGSCAB00JSJS1900683；SGSCDZ00JSJS2100272）

详细信息

作者简介: 任光明（1964—），男，硕士，教授，主要从事工程地质与岩土工程的研究工作。E-mail：rengmgcr@163.com

通讯作者: 李海涛（1998—），男，硕士研究生，主要从事岩土工程的研究。E-mail：1965347983@qq.com

中图分类号: TU473

收稿日期: 2023-04-19

修回日期: 2023-06-18

刊出日期: 2024-03-15

Bearing characteristics of variable diameter micropile based on the improvement of group pile foundation

1.
State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Chengdu University of Technology, Chengdu, Sichuan　610059 China

2.
State Grid Sichuan Economic Research Institute, Chengdu, Sichuan　610041 China

More Information

Corresponding author: LI Haitao, 1965347983@qq.com

Received Date: 19 April 2023

Revised Date: 18 June 2023

Publish Date: 15 March 2024

摘要

摘要:
为改善输电杆塔微型桩基础的承载特性、降低用料成本，提出基于微型群桩改进的变径微型桩基础型式。通过高原山区等截面微型群桩原型试验与数值反演模型相互验证，对3种变径微型单桩进行模拟，并与微型群桩承载效果进行对比分析，揭示变径微型桩的承载特征与变形机理。结果表明：微型群桩基础（2×2单桩）由于承台和群桩效应的影响，其抗压和抗拔承载力分别大于和小于对应的单桩承载力总和；双扩径微型桩（扩径部分直径=2×等截面桩身直径）的极限抗拔和抗压承载力约为等截面微型桩的3.8倍和2.7倍，土体变形集中于扩径部位，且变形量较大，表现为多支点摩擦−端承桩特性；于桩顶增设承台可有效改善双扩径单桩的下压及水平承载性能，与未增设承台相比，承载力分别提高了2.1倍和2.2倍。研究表明，通过扩展部分桩径并增设承台使微型单桩性能提升至等截面群桩水平的方法可行，对送变电建设具有工程意义。
- 送变电工程 /
- 等截面微型群桩 /
- 原型试验 /
- 数值模拟 /
- 变径微型桩 /
- 承载力特征
Abstract:
To improve the load-bearing of transmission tower micropile foundation and reduce the material cost, a modified variable diameter micropile foundation type based on group micropile is proposed in this study. The bearing characteristics and deformation mechanism of variable diameter miniature pile were revealed by simulation with three kinds of variable diameter miniature micropiles and comparison with the bearing effect of micropile group pile, using the prototype test and numerical inversion model of micropile group pile with equal section in the highland mountainous area. The results show that the compressive and pullout bearing capacities of micropile group foundation (2×2 single pile) are greater and less than the total of corresponding single pile bearing capacity, respectively, due to the effect of bearing platform and group pile effect. The ultimate pullout and compressive bearing capacities of double diameter-extended micropile (the diameter of the dilated part = 2 × the diameter of the equal) is approximately 3.8 times and 2.7 times of the equal section micropile. The soil deformation is concentrated in the dilated part with large deformation value, which presents the characteristics of multi-fulcrum friction-end bearing pile. The addition of cap can improve the downward pressure and horizontal bearing capacity of double-expanded micropile effectively, which increase 2.1 times and 2.2 times compared to that in the situation of no cap, respectively. This study indicates that improving the performance of single micropile to the level of equal section group micropiles by extending part of the pile diameter is feasible and has engineering significance for the transmission and substation construction.
- electricity transmission /
- equal section micropile group /
- prototype test /
- numerical simulation /
- variable diameter micropile /
- characteristics of bearing capacity

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图 1 土体颗粒分析曲线

Figure 1.

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图 2 应力计布设

Figure 2.

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图 3 试验加载装置及平面布置

Figure 3.

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图 4 桩周土体裂隙发育

Figure 4.

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图 5 桩身轴力分布和桩侧摩阻力曲线

Figure 5.

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图 6 荷载−位移曲线对比

Figure 6.

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图 7 地基土及微型群桩模型

Figure 7.

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图 8 变径微型桩施工概念和变径微型桩施工效果及承载机理

Figure 8.

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图 9 变径微型桩模型示意图

Figure 9.

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图 10 变径微型桩抗拔、抗压和抗水平承载特征研究

Figure 10.

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图 11 双扩径微型桩+承台

Figure 11.

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图 12 双扩径微型桩+承台承载特征研究

Figure 12.

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图 13 微型桩极限承载力对比

Figure 13.

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表 1 试验场地土层物理力学参数

Table 1. Physical and mechanical parameters of soil layers at the test site

试样编号	取样深度/m	含水率 /%	塑性指数	压缩模量 /MPa	泊松比	黏聚力 /kPa	内摩擦角 /（°）
1-1	0～3.0	22.94	12.5	14.9	0.33	12.50	25.60
1-2	0～3.0	20.12	13.0	15.3	0.32	14.89	28.45
2-1	3.0～3.9	19.89	11.6	18.8	0.30	20.47	15.05
3-1	5.2～6.2	22.18	14.5	19.4	0.29	23.08	17.39
3-2	5.2～6.2	21.86	14.8	21.5	0.30	23.61	17.87
4-1	8.0～9.0	24.43	15.1	15.4	0.32	17.18	30.49

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表 2 土体和桩体计算参数取值

Table 2. Parameters of soil and pile

名称	深度 /m	密度 /（g∙cm⁻³）	弹性模量 /MPa	泊松比	内摩擦 /（°）	黏聚力 /kPa
粉土质砾	0～3	2.09	4.9	0.32	27.03	13.70
粉土质砂	>3	2.13	8.2	0.30	16.77	21.39
桩体		2.50	31.5	0.20

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