岩溶区桥桩承载特性及溶洞变形机理研究

赵桂清; 张吉禄; 周小涵; 刘新荣; 刘馨琳; 郭宏青

doi:10.11932/karst20240510

岩溶区桥桩承载特性及溶洞变形机理研究

doi: 10.11932/karst20240510

赵桂清^1,,
张吉禄^{2, 3, ,},
周小涵^{2, 3},
刘新荣^{2, 3},
刘馨琳^{2, 3},
郭宏青¹

1.
中国水利水电第十四工程局有限公司, 云南昆明 650041
2.
重庆大学土木工程学院, 重庆 400045
3.
库区环境地质灾害防治国家地方联合工程研究中心（重庆）, 重庆 400045

基金项目: 国家自然科学基金青年基金项目（52104076）

详细信息

作者简介:
赵桂清（1978－），男，工程师，主要从事道路桥梁方面的施工技术与工程管理。E-mail：512935371@qq.com

通讯作者:
张吉禄（1993－），男，博士研究生，主要从事岩土工程与桩基础方面的研究与设计工作。E-mail：540726390@qq.com。

中图分类号: TU443.1：P642.25
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出版历程
- 收稿日期: 2023-01-01
- 录用日期: 2024-01-12
- 网络出版日期: 2024-12-30
- 刊出日期: 2024-10-25

Study on bearing characteristics of bridge piles and deformation mechanisms of karst caves in karst area

ZHAO Guiqing^1
,,
ZHANG Jilu^{2, 3
, ,},
ZHOU Xiaohan^{2, 3},
LIU Xinrong^{2, 3},
LIU Xinlin^{2, 3},
GUO Hongqing¹

1.
SINOHYDRO Bureau 14 Co., LTD., Kunming, Yunnan 650041, China
2.
School of Civil Engineering, Chongqing University, Chongqing 400045, China
3.
National Joint Engineering Research Center of Geohazards Prevention in the Reservoir Areas (Chongqing), Chongqing 400045, China

摘要

摘要: 为明确岩溶区桥梁建设过程中溶洞对桥桩承载特性的影响机理，以贵州某高速公路项目高架桥桩为依托，采用数值模拟的方法研究桥桩整体穿越溶洞、侧穿溶洞以及临近溶洞情况下桩基承载能力、桩身荷载传递规律以及溶洞稳定性。结果表明：（1）当桥桩穿越溶洞时，桥桩承载能力随溶洞埋深增加而降低，文中工况下承载力最大衰减量为16.5%~17.5%，而当桥桩临近溶洞时，溶洞对桥桩的影响随距离增加而减小，且当水平距离大于2D后（D为桩身直径）影响可忽略不计；（2）当溶洞位于桩身嵌岩段上部且桥桩侧穿溶洞或桥桩临近溶洞不足1D时，桥桩将产生较大差异沉降，进而影响上部结构稳定性；（3）溶洞的存在主要影响桩基临空段侧阻力的发挥，而对其他位置侧阻力的发挥影响不大，且溶洞对端阻力影响程度排序为：桥桩整体穿越溶洞>桥桩侧穿溶洞>桥桩临近溶洞；（4）桥桩整体穿越、侧穿以及临近溶洞引起的溶洞潜在破坏模式分别为顶板拉伸破坏、桩基位置附近剪切破坏以及承台的冲切破坏。
- 桥桩 /
- 溶洞 /
- 承载特性 /
- 稳定性；岩溶区
Abstract: Due to the highly undulating terrain, complex geological conditions, and the widespread distribution of karst topography developed with underground karst caves in Southwest China, the construction of bridges and tunnels will inevitably traverse areas that contain these karst caves. The karst effect changes the structure of rock masses, weakening the strength and increasing the permeability of the surrounding soil. In regions where caves are developed, the construction of pile foundations will not only encounter challenges in pile formation but also will experience impacts on the load-bearing capacity of foundations due to the presence of these caves. Prolonged loads can easily result in severe deformations, tilting, or even collapses of the superstructure. To elucidate the impact mechanisms of caves on the bearing characteristics of bridge piles during construction in karst regions, this study focused on viaduct piles from a highway project in Guizhou. Numerical simulations were employed to examine the settlement patterns of piles that completely traversed the cave, those that laterally intersected with the cave, and those that were adjacent to caves. Furthermore, the axial force distribution in the piles and the deformation characteristics of the caves were analyzed, along with the stability of the caves under various working conditions.The research findings indicate as follows, (1) Caves reduce the bearing capacity of bridge piles, although the degree of this effect varies by location. When bridge piles are situated near caves, the influence diminishes with increasing distance, becoming negligible when the horizontal distance exceeds 2D (where D represents the pile diameter). Conversely, when bridge piles pass through caves, their bearing capacity decreases as the burial depth of the caves increases. The maximum impact occurs when the cave is located directly beneath the rock-embedded section of the pile, resulting in a reduction of bearing capacity by approximately 16.5% to 17.5%. Engineering practices should give due consideration to caves near the pile tips. (2) The asymmetric distribution of caves contributes to differential settlement of the foundation. The shallower the cave or the closer it is to the bridge pile, the more significant the impact. Specifically, when the cave is located above the rock-embedded section of the pile or is less than 1D away from the bridge pile, it is necessary to implement reinforcement measures such as backfilling or grouting to prevent excessive differential settlement of the foundation. (3) For end-bearing piles, the influence of the cave on the side resistance of the pile mainly manifests as a loss of side resistance in the exposed section of the pile foundation. The impact of caves on end resistance is ranked as follows: piles fully traversing the cave>piles laterally crossing the cave>piles near the cave. (4) When bridge piles fully traverse the cave, the predominant failure mode of the cave is tensile failure of the roof. When bridge piles laterally cross the cave, shear failure primarily occurs near the pile foundation. When bridge piles are in close proximity to the cave, the potential failure mode is punching shear failure from the foundation. (5) When bridge piles cross the cave, it is crucial to consider the impact of the loads on the stability of the cave and to implement appropriate reinforcement measures. Additionally, when bridge piles are near the cave, caution must be exercised regarding the potential for localized instability of the cave if the distance is too short (<0.5D).
- bridge pile /
- karst cave /
- bearing characteristics /
- stability, karst area

HTML

图 1 桥梁设计及溶洞分布

Figure 1. Bridge design and distribution of the karst caves

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图 2 桥桩设计方案

Figure 2. Design of bridge piles

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图 3 数值计算模型

Figure 3. Model of numerical calculation

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图 4 不同计算工况溶洞位置

Figure 4. Positions of karst caves under different working conditions of calculation

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图 5 荷载-位移曲线

Figure 5. Load-deformation curves

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图 6 承台沉降曲线

Figure 6. Settlement curve of pile cap

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图 7 桥桩整体穿越溶洞轴力分布曲线

Figure 7. Distribution curve of axial force of bridge piles crossing the karst cave

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图 9 桥桩临近溶洞轴力分布曲线

Figure 9. Distribution curve of axial force of bridge piles located near the karst cave

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图 8 桥桩侧穿溶洞轴力分布曲线

Figure 8. Distribution curve of axial force of bridge piles passing through the karst cave from one side

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图 10 溶洞顶板位移

Figure 10. Roof displacement of the karst cave

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图 11 溶洞顶板最大位移分布曲线

Figure 11. Distribution curve of maximum displacement of the karst cave roof

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表 1 桥桩材料参数

Table 1. Material parameters of bridge piles

名称	密度ρ/g·cm⁻³	弹性模量E(GPa)	泊松比μ
桥桩	2.5	20	0.15

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表 2 岩土体材料参数

Table 2. Material parameters of rock and soil

名称	深度 H_i/m	密度 ρ/g·cm⁻³	压缩模量 E_s/MPa	泊松比 μ	粘聚力 c/kPa	摩擦角 φ/°
黏土	3	1.8	6.6	0.3	25	8
灰岩	77	2.6	2 000	0.25	110	32

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表 3 模拟工况信息

Table 3. Information of simulated information

工况	类型	溶洞位置
工况	类型	竖向	水平
1	无溶洞	/	/
2	整体穿越溶洞	H₂/6	/
3	整体穿越溶洞	H₂/2	/
4	整体穿越溶洞	5 H₂/6	/
5	侧穿溶洞	H₂/6	/
6	侧穿溶洞	H₂/2	/
7	侧穿溶洞	5 H₂/6	/
8	临近溶洞	H₂/6	0.5D
9	临近溶洞	H₂/6	1D
10	临近溶洞	H₂/6	2D
（其中H₂/6，H₂/2，5H₂/6对应实际距离分别为3.8 m，12.5 m，19.2 m） (H₂/6, H₂/2, and 5H₂/6 correspond to the actual distance of 3.8 m, 12.5m, 19.2 m, respectively)

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表 4 桥桩极限荷载与位移

Table 4. Ultimate load and displacement of bridge piles

工况	极限荷载/kN	承载力衰减系数 /%	桩顶位移/mm	桩底位移/mm	桩身压缩量/mm
1	121 941.8	/	40	20.09	19.91
2	105 271.0	13.67	40	22.46	17.54
3	105 760.1	13.27	40	23.56	16.44
4	101 825.6	16.50	40	24.40	15.60
5	107 852.9	11.55	40	22.67	17.33
6	109 358.8	10.32	40	23.06	16.94
7	100 505.5	17.58	40	23.89	16.11
8	115 146.8	5.57	40	21.88	18.12
9	117 801.9	3.39	40	21.57	18.43
10	123 774.4	−1.50	40	20.63	19.37

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