大直径超长桩自平衡检测法极软岩转换系数研究

陈怡坛; 张容; 李忠伟

doi:10.20265/j.cnki.issn.1007-2993.2024-0451

大直径超长桩自平衡检测法极软岩转换系数研究

doi: 10.20265/j.cnki.issn.1007-2993.2024-0451

陈怡坛^1,,
张容²,
李忠伟^{1, 3, ,}

1.
南京东大自平衡桩基检测有限公司，江苏南京　211164
2.
湖北伟兴建设有限公司，湖北荆州　434300
3.
东南大学土木工程学院，江苏南京　211189

详细信息

作者简介:
陈怡坛，男，1990年生，大学本科，工程师，主要从事岩土工程施工技术研究。E-mail：Chenytbr@outlook.com

通讯作者:
李忠伟，男，1992年生，博士，主要从事桩基础、桥梁基础研究。E-mail：lizw@seu.edu.cn

中图分类号: TU473.1+6
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- 文章访问数: 3
- HTML全文浏览量: 3
- PDF下载量: 1
- 被引次数: 0
出版历程
- 收稿日期: 2024-10-03
- 修回日期: 2024-12-27
- 录用日期: 2025-04-09
- 网络出版日期: 2026-04-09
- 刊出日期: 2026-04-09

Conversion coefficient of extremely soft rock by Osterberg Cell Testing of large diameter ultra-long pile

CHEN Yitan^1
,,
ZHANG Rong²,
LI Zhongwei^{1, 3
, ,}

1.
Nanjing Dongda Self-Balancing Pile Foundation Testing Co., Ltd., Nanjing 211164, Jiangsu, China
2.
Hubei Weixing Construction Co., Ltd., Jingzhou 434300, Hubei, China
3.
School of Civil Engineering, Southeast University, Nanjing 211189, Jiangsu, China

摘要

摘要: 自平衡检测法是一种高效的基桩承载力测试技术，实现了复杂环境中单桩承载力的直接测量，该方法中的关键计算参数为转换系数，然而关于极软岩条件下转换系数的合理取值却鲜有研究。依托南京龙潭长江大桥主塔桩基础，开展原位自平衡试验，获取了极软岩地层的试验结果。考虑上段桩桩侧承载力弱化效应，建立三维有限元模型，模拟了自平衡试验过程，并基于试验与模拟数据对比，对转换系数取值进行定量分析。研究结果表明，极软岩地层中桩基转换系数取0.9时，模拟结果与实测结果最为接近；在极软岩条件下，转换系数的修正使桩基极限承载力和承载力特征值增大，从而有助于提高承载力评价的合理性，并为工程设计提供更加经济合理的取值依据。研究结果可为类似地质条件下的基桩自平衡检测试验参数取值提供参考。
- 自平衡检测法 /
- 基桩承载力 /
- 极软岩 /
- 转换系数 /
- 有限元模型
Abstract: As an efficient test technique for pile bearing capacity, Osterberg Cell (O-Cell) testing can directly measure the bearing capacity of single pile in complex environment. However, few studies have been conducted on the reasonable value of the key calculation parameter γ in this method under extremely soft rock conditions. Based on the pile foundation of the main tower of Nanjing Longtan Yangtze River Bridge, the in-situ O-Cell testing was carried out and the test results of extremely soft rock stratum were obtained. Considering the weakening effect of the side bearing capacity of the upper section pile, a three-dimensional finite element model is established to simulate the O-Cell testing process, and the conversion coefficient is quantitatively analyzed based on the comparison between the test and the simulated data. The results show that the simulated results are most close to the measured results when the pile foundation conversion coefficient γ is 0.9 in the very soft rock formation. Under extremely soft rock conditions, the modification of the conversion coefficient leads to an increase in both the ultimate bearing capacity and the characteristic bearing capacity of pile foundations, thereby improving the rationality of bearing capacity evaluation and providing a more reasonable basis for capacity selection in engineering design. The research results can provide reference for self-balancing test parameters under similar geological conditions.
- Osterberg Cell Testing /
- bearing capacity of foundation piles /
- extremely soft rock /
- conversion coefficient /
- finite element model

HTML全文

图 1 试桩位置平面图（单位：m）

Figure 1. Layout of test pile (Unit：m)

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图 2 试桩地质剖面图

Figure 2. Geological profile of test pile

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图 3 自平衡试验系统剖面图

Figure 3. O-cell test system profile

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图 4 基准系统剖面及平面布置图

Figure 4. Reference system profile and layout plan

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图 5 试验桩桩身仪器布设剖面示意图

Figure 5. Test pile instrument layout profile

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图 6 试验系统现场搭建

Figure 6. Construction of the test system

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图 7 试验桩荷载位移曲线

Figure 7. Load-displacement curves of the test pile

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图 8 试验桩时间位移曲线

Figure 8. Time-displacement curves of the test pile

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图 9 等效荷载位移曲线

Figure 9. Equivalent load-displacement curve

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图 10 试验桩模型

Figure 10. The test pile model

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图 11 试验桩受力示意图

Figure 11. The test pile force diagram

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图 12 模型网格划分剖面图

Figure 12. Model meshing section

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图 13 R_inter=0.8模型竖向位移

Figure 13. Model vertical displacement when R_inter=0.8

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图 14 数值模型荷载位移曲线

Figure 14. Load-displacement curves of the models

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图 15 等效荷载位移曲线及整桩模拟竖向位移

Figure 15. Equivalent load-displacement and vertical displacement of the whole pile

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表 1 试桩加卸载分级表

Table 1. Test pile loading and unloading classification

加载阶段		卸载阶段
级数	荷载/kN	级数	荷载/kN
1	2×4600	16	2×55200
2	2×9200	17	2×41400
3	2×13800	18	2×27600
4	2×18400	19	2×13800
5	2×23000	20	0
6	2×27600
7	2×32200
8	2×36800
9	2×41400
10	2×46000
11	2×50600
12	2×55200
13	2×59800
14	2×64400
15	2×69000

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表 2 试验桩穿越地层信息

Table 2. Strata information traversed by test pile

地层	层底埋深/m	极限侧阻力标准值q_ik/kPa	承载力特征值q_r/kPa
中等风化粉砂质泥岩	81.42	150
疏松砂岩	88.22	90
弱胶结含砾砂岩	92.00	140	500

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表 3 模型材料参数

Table 3. Model material parameters

材料	底部埋深/m	重度γ/（kN·m⁻³）	弹性模量E/kPa	饱和单轴抗压强度σ_c/kPa	岩性指标m_i	地质强度指标GSI	扰动指数D	黏聚力c/kPa	内摩擦角φ/（°）
中等风化粉砂质泥岩	84.2	23.0	126200.0	4200	7	50	0
疏松砂岩	92.0	21.0	122520.0	4980	7	50	0
弱胶结含砾砂岩	110.0	20.1	153827.2	5620	7	50	0
含粒砂岩	150.0	22.6	171387.6	8832	7	60	0
桩身		25.0	30000000.0					30000	50

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表 4 模拟工况

Table 4. Working conditions of the simulation

R_inter=0.7		R_inter=0.8		R_inter=0.9		R_inter=1.0
工况号	荷载/kN	工况号	荷载/kN	工况号	荷载/kN	工况号	荷载/kN
1-1	9200	2-1	9200	3-1	9200	4-1	9200
1-2	13800	2-2	13800	3-2	13800	4-2	13800
1-3	18400	2-3	18400	3-3	18400	4-3	18400
1-4	23000	2-4	23000	3-4	23000	4-4	23000
1-5	27600	2-5	27600	3-5	27600	4-5	27600
1-6	32200	2-6	32200	3-6	32200	4-6	32200
1-7	36800	2-7	36800	3-7	36800	4-7	36800
1-8	41400	2-8	41400	3-8	41400	4-8	41400
1-9	46000	2-9	46000	3-9	46000	4-9	46000
1-10	50600	2-10	50600	3-10	50600	4-10	50600
1-11	55200	2-11	55200	3-11	55200	4-11	55200
1-12	59800	2-12	59800	3-12	59800	4-12	59800
1-13	64400	2-13	64400	3-13	64400	4-13	64400
1-14	69000	2-14	69000	3-14	69000	4-14	69000

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