复杂岩溶地区的钢护筒群承载机理数值模拟研究

郭辉; 牟云贞; 仉文岗; 陈斐; 张艳梅; 王硕; 林思成

doi:10.11932/karst2024y012

复杂岩溶地区的钢护筒群承载机理数值模拟研究

doi: 10.11932/karst2024y012

郭辉^1,,
牟云贞²,
仉文岗^3, ,,
陈斐²,
张艳梅³,
王硕³,
林思成³

1.
江西省港口集团, 江西九江 330008
2.
长江重庆航道工程局, 重庆 400011
3.
重庆大学, 重庆 400044

基金项目: 长江重庆航道工程局科技项目（H20230330）；四川省交通运输科技项目（2018-ZL-01）

详细信息

作者简介:
郭辉（1988-）男，工程师，主要从事公路水运工程施工项目管理。E-mail: 804071291@qq.com

通讯作者:
仉文岗（1983－），男，教授，博士，主要从事地质灾害防治研究。E-mail：zhangwg@cqu.edu.cn。

中图分类号: U656.1
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- 被引次数: 0
出版历程
- 收稿日期: 2023-07-04
- 录用日期: 2024-02-18
- 修回日期: 2023-10-18
- 刊出日期: 2025-02-25

Numerical simulation of bearing mechanism of steel casing group in complex karst area

1.
Jiangxi Port Group, Jiujiang, Jiangxi 330008, China
2.
Yangtze River Chongqing Waterway Engineering Bureau, Chongqing 400011, China
3.
Chongqing University, Chongqing 400044, China

摘要

摘要: 岩溶区桩基施工过程中，隐伏溶洞空间分布的不确定性导致施工过程风险性提高，尤其是搭设钢护筒时，结构荷载超过钢护筒侧摩阻力，可导致钢护筒下沉对施工工作面带来安全风险。文章以江西九江银沙湾复杂岩溶区桩基施工工程为例，模拟研究了岩溶区钢护筒群的承载特性。结果表明：整个施工区域岩溶非常发育，溶洞占比为76.2%，溶洞的最大高度为17.3 m，且存在大溶洞串洞现象。按照大溶洞区空间分布特点，钢护筒群下沉模式分为三种，三角形区钢护筒群下沉、矩形区钢护筒群下沉和单排型钢护筒群下沉。提出预设指定位移来反分析钢护筒群下沉过程的模拟方法，模拟结果显示，隐伏大溶洞区施工方式应该按照外侧优先成桩，内侧选点成桩方式进行。
- 岩溶区 /
- 钢护筒 /
- 承载特性 /
- 数值模拟 /
- 失效分析
Abstract: The construction of pile foundations in karst areas presents unique challenges due to the unpredictable spatial distribution of underground cavities, which may significantly increase the associated risk of such projects. Karst topography is characterized by the presence of soluble rocks, such as limestone, which have been gradually dissolved by groundwater, resulting in the formation of crevices and caves. This geological feature poses significant difficulties for engineers, as the unpredictability of these subsurface formations can lead to complications during construction, especially when steel casings are installed for pile foundations. In karst areas, the risk to the construction process tends to be exacerbated by the possibility of encountering covered caves.When steel casings are built, the structural load may exceed the side friction of the casings, potentially causing them to sink. This situation escalates the construction risks, making the project more complex and challenging. The project for pile foundation construction in the complex karst area of Yinshawan, Jiujiang, Jiangxi (hereinafter referred to as the Yinshawan Project), exemplifies such challenges associated with this type of environment. This area is highly karstic, with caves constituting 76.2% of the karst topography and the largest cave reaching a height of 17.3 m. These characteristics require an improved approach to steel casing construction to prevent sinking and collapse. To solve these issues, this study introduces a three-dimensional numerical model that incorporates the presence of caves, informed by preliminary drilling data and exploration conditions specific to the Yinshawan Project. This model is a critical tool for understanding the subsidence behavior of steel casings in karst areas. This study classifies subsidence patterns into three distinct categories: single-row steel casing groups, triangular steel casing groups, and rectangular steel casing groups. It examines the mechanics of steel casing subsidence in areas affected by karst development. The method involves simulating specified displacements to retroactively analyze the sinking process of steel casing groups. Through numerical simulations, this study examined the load-bearing characteristics of steel casing groups in various sinking modes. The findings reveal that the sinking modes differed significantly in terms of the maximum longitudinal and transverse bending moments experienced by the casings. For instance, in the single-row steel casing group, the maximum longitudinal bending moment was found to be 1,620 kN·m, while the maximum transverse bending moment was 664.6 kN·m. In the sinking mode of the steel casing group within the rectangular area, the maximum transverse bending moment in the non-sinking steel casing was 637.8 kN·m, and the maximum longitudinal bending moment was 2,144 kN·m; both of these values were found in the same steel casing. In the sinking mode of the triangular steel casing group, the maximum longitudinal bending moment in the non-sinking steel casing was 2,090 kN·m, and the maximum transverse bending moment was 922.2 kN·m. The study offers detailed analysis of each sinking mode, highlighting the stress characteristics and potential risks of subsidence. Given these risks and the specific stress characteristics identified through simulations, a construction method in areas with significant covered caves, such as the project site in Yinshawan, should be prioritized. This method should focus on peripheral piling while selectively placing piles in the interior. This study provides valuable insights into the field of geotechnical engineering, offering guidance for future projects in similarly challenging environments.
- karst area /
- steel casing /
- bearing characteristics /
- numerical simulation /
- failure analysis

HTML

图 1 银沙湾码头平面布置图

Figure 1. Layout of Yinshawan Wharf

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图 2 施工平台布置示意图

Figure 2. Layout of construction platform

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图 3 不同类型大小溶洞占比

Figure 3. Proportions of karst caves with different sizes

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图 4 隐伏大溶洞空间分布

Figure 4. Spatial distribution of large covered karst caves

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图 5 钢护筒群下沉风险分类

注：(a) 单排型钢护筒群失效， (b) 矩形区钢护筒群失效， (c) 三角形区钢护筒群失效。

Figure 5. Classification of sinking risk of steel casing groups

Note: (a) Failure of single-row steel casing group; (b) Failure of rectangular steel casing group; (c) Failure of triangle steel casing group.

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图 6 数值模型示意图

Figure 6. Schematic diagram of the numerical model

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图 7 承载力计算结果

Figure 7. Calculation result of bearing capacity

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图 8 沉降位移云图

Figure 8. Cloud map of settlement displacement

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图 9 未成桩区弯矩与轴力最大值点

注：(a)纵向弯矩点：钢护筒B3，(b)横向弯矩点：钢护筒B4， (c)轴力点：钢护筒B4。

Figure 9. Maximum point of bending moment and axial force in the unformed pile area

Note: (a) Point of longitudinal bending moment point: steel casing B3; (b) Point of transverse bending moment point: steel casing B4; (c) Point of axial force: steel casing B4.

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图 10 承载力计算结果

Figure 10. Calculation result of bearing capacity

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图 11 沉降位移云图

Figure 11. Cloud map of settlement displacement

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图 12 未成桩区弯矩与轴力最大值点

注：(a)纵向弯矩点：钢护筒C2，(b)横向弯矩点：钢护筒C2， (c)轴力点：钢护筒C3。

Figure 12. Maximum point of bending moment and axial force in the unformed pile area

Note: (a) Point of longitudinal bending moment: steel casing C2; (b)Point of transverse bending moment point: steel casing C2; (c) Point of axial force point: steel casing C3.

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图 13 承载力计算结果

Figure 13. Calculation results of bearing capacity

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图 14 沉降位移云图

Figure 14. Settlement displacement cloud map

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图 15 未成桩区弯矩与轴力最大值点

注：(a)纵向弯矩点：钢护筒C3， (b)横向弯矩点：钢护筒C4，(c)轴力点：钢护筒B4。

Figure 15. Maximum points of bending moment and axial force in the unformed pile area

Note: (a) Point of longitudinal bending moment: steel casing C3; (b) Point of transverse bending moment: steel casing C4; (c) Point of axial force : steel casing B4.

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表 1 钢平台面荷载统计表

Table 1. Statistics of steel platform surface load

	荷载类型	面荷载/kN·m⁻²
恒载	钢面板自重	0.69
	横梁自重	0.38
	纵梁自重	0.64
	栏杆自重	0.06
	钢管柱及钢横撑自重	20.50
	钢横撑自重	1.27
活载	施工荷载	2.00
	机械荷载	1.65
	水流荷载	1.17

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表 2 岩土材料参数

Table 2. Geotechnical material parameters

	重度/kN·m⁻³	弹性模量E₅₀/ kN·m⁻²	黏聚力C/ kN·m⁻²	摩擦角Φ/°
抛石	22.0	1.00×10⁵	27.5	45
粉质黏土	18.8	6.37×10³	19.0	11
粉细砂1	19.0	1.17×10⁴	3.0	21
粉细砂2	20.0	1.56×10⁴	0	28
粉细砂3	20.0	2.21×10⁴	0	31
灰岩	21.8	1.00×10⁵	2.5×10⁴	60

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表 3 梁与钢护筒参数

Table 3. Beam and steel casing parameters

	重度/kN·m⁻³	弹性模梁E₅₀ /N·m⁻²	截面面积/m²	惯性矩I₂ /m⁴	极限侧摩阻力标准值/kN	极限端阻力标准值/kN
梁	78.5	2×10¹¹	9.5×10⁻³	7.19×10⁻⁶	\	\
钢护筒	78.5	2×10¹¹	5.0×10⁻³	2.01×10⁻⁶	70~350	\
混凝土桩	25.0	3×10¹⁰	1.65	2.17×10⁻¹	100~600	4500

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