隐伏溶洞对机场地表稳定性影响模拟及处治技术

余虔; 王成成; 张莎莎; 寇璟媛; 王志丰

doi:10.11932/karst20240508

隐伏溶洞对机场地表稳定性影响模拟及处治技术

doi: 10.11932/karst20240508

1.
民航机场规划设计总院有限公司，北京 100120
2.
长安大学公路学院，陕西西安 710064

基金项目: 国家自然科学基金项目(52178310)；民航机场规划设计研究总院有限公司科研项目（220221220342）

详细信息

作者简介:
余虔（1984－），男，硕士，高级工程师，研究方向：机场岩土工程设计。E-mail：370912441@qq.com

通讯作者:
张莎莎（1982－），女，博士，副教授，硕士研究生导师，主要从事地基处理及地下工程等的教学和科研工作。E-mail：zss_lx@126.com。

中图分类号: TU457
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出版历程
- 收稿日期: 2023-11-07
- 网络出版日期: 2024-12-30
- 刊出日期: 2024-10-25

Impact of concealed karst caves on airport surface stability and treatment techniques

1.
China Airport Planning and Design Institute Co., Ltd., Beijing 100120, China
2.
School of Highway, Chang'an University, Xi'an, Shaanxi 710064, China

摘要

摘要: 广州白云国际机场扩建过程中岩溶强烈发育，严重影响机场施工安全。文章采用FLAC3D数值模拟软件分析隐伏溶洞在不同厚跨比、高跨比及道基填筑厚度下对机场场区稳定性的影响规律，并针对溶洞处治前后稳定性进行评价，最后通过现场试验比较溶洞充填自密实土、泡沫混凝土及低标号混凝土的优缺点并进行处治效果评价。结果表明：当厚跨比及高跨比减小，道基填筑高度增大时，溶洞位移及应力呈现增加趋势，整体趋近于不稳定状态；当厚跨比>1或高跨比>2时，地基稳定；对典型工况溶洞注浆处治后，顶板竖向位移量最大为0.6 mm，降低99.11%，应力集中现象极大减弱。在广州白云机场溶洞处理施工中应优先采用低标号混凝土作为填充料进行大面积施工，其次采用泡沫混凝土；钻孔取芯法及孔内波速测井法检测表明溶洞处理效果良好。
- 隐伏溶洞 /
- 机场 /
- 应力变化 /
- 数值模拟 /
- 稳定性评价 /
- 混凝土注浆
Abstract: If an airport is built in a karst area, a concealed karst cave will pose a challenge to the airport construction because of its concealment. The adverse geological effects in the site area of the third phase expansion project of Guangzhou Baiyun international airport are significantly pronounced. The roof thickness of 132 exposed karst caves ranges from 0.1 m to 5.2 m, the height varies from 0.7 m to 13.5 m, the span measures between 0.5 m and 11.7 m, and the buried depth ranges from 13.2 m to 32.7 m. Most of the karst caves exhibit no filling or poor filling properties. The groundwater at the site consists of loose rock pore water, with a water level depth of 4.38 m. The bedrock is mainly composed of soluble limestone. Additionally, the rock mass in the engineering site exhibits significant folding. Affected by the Guangcong Fault, many secondary faults are developed, and the brittle rock mass is easily broken. Consequently, the action of external forces such as foundation construction and road rolling likely cause the breakage of cave roofs and uneven settlement of ground, which is not conducive to the safe construction of airport pavement. Therefore, the stability evaluation and treatment technique of karst foundation are very important to the smooth completeness of this project.Based on the FLAC3D numerical simulation method, a 100 m×50 m×50 m three-dimensional calculation model was established to analyze the influence of different thickness-span ratios and high-span ratios of concealed karst caves on the stability of the airport site under the filling load of the roadbed. A comparative analysis was conducted to evaluate the displacement, plastic zone, and stress of typical karst caves before and after treatment, providing a comprehensive assessment of their stability. Finally, a field test was carried out with the combination of high-pressure pouring of low-grade concrete and sleeve valve pipe grouting. The treatment effects of filling karst caves with self-compacting soil, foam concrete, and low-grade concrete were compared and analyzed through various methods, including by core drilling, borehole wave velocity logging, geophysical prospecting tests, standard penetration tests, compressibility tests, and wave velocity profiling.The results show that when the thickness-span ratio and height-span ratio of a concealed karst cave decrease and the filling height of the subgrade increases, the displacement and stress of the karst cave show an increasing trend and tend to be unstable as a whole. Compared with the span of the cave, the roof thickness is relatively insufficient, and the bearing capacity is inadequate to bear the upper load. This presents potential risks of roof breakage and cave collapse. It can be concluded that the cave will significantly affect the stability of the airport. When the thickness-span ratio (K_H) is greater than 1 or the height-span ratio (K_G) is greater than 2 for the concealed karst cave, the whole cave tends to be stable, indicating a high level of its stability. After addressing the typical working conditions of karst caves through a combination of high-pressure perfusion of low-grade concrete and sleeve valve tube grouting, it has been found that the displacement of the roof of the karst cave following the treatment of low-grade concrete grouting is only 0.6 mm. This represents a reduction of 99.11% compared to conditions without treatment. The phenomenon of stress concentration is significantly reduced, resulting in enhanced foundation strength and effective grouting outcomes. Based on the comparative analysis of numerical calculation and field test, it is proposed that low-grade concrete should be preferentially used as filling material in the treatment of concealed karst caves in the third phase expansion project of Guangzhou Baiyun airport, followed by foam concrete. This study can provide reference for the selection of karst treatment measures in South China.
- concealed karst cave /
- airport /
- stress variation /
- numerical simulation /
- stability evaluation /
- concrete grouting

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图 1 工程场区区域地质图

Figure 1. Regional geological map of the project site

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图 2 地层位移监测点布置图

Figure 2. Layout of monitoring points for strata displacement

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图 3 不同厚跨比机场场区位移与应力变化

Figure 3. Variations of displacement and stress with different thickness-span ratios in the airport

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图 4 不同高跨比机场场区位移与应力变化

Figure 4. Variations of displacement and stress with different height-span ratios in the airport

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图 5 不同道基填筑厚度机场场区位移与应力变化

Figure 5. Variations of displacement and stress with different thicknesses of embankment filling in the airport

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图 6 监测点竖向位移曲线及塑性区云图

Figure 6. Vertical displacement curves of monitoring points and cloud map of plastic region

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图 7 监测点最大、最小主应力曲线及云图

Figure 7. Curves and nephograms of maximum and minimum principal stress of monitoring points

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图 8 处治后监测点竖向位移曲线及塑性区云图

Figure 8. Curves of the vertical displacement of monitoring points and the cloud image of plastic region after treatment

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图 9 处治后监测点最大、最小主应力曲线及云图

Figure 9. Maximum and minimum principal stress curves and nephograms of the monitoring points after treatment

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图 10 处治后监测点竖向位移曲线图

Figure 10. Vertical displacement curves of monitoring points after treatment

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图 11 处治后监测点主应力曲线图

Figure 11. Principal stress curves of monitoring points after treatment

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图 12 RX20-T7测线布置及波速剖面图

Figure 12. Layout of Line RX20-T7 and profile of wave velocity

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图 13 TRX26-T1测线布置及波速剖面图

Figure 13. Layout of Line TRX26-T1 and profile of wave velocity

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图 14 TX20-T测线布置及波速剖面图

Figure 14. Layout of Line TX20-T and profile of wave velocity

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表 1 钻孔揭示的场区溶洞发育情况

Table 1. Development of karst caves revealed by drilling holes in the project

埋深/m	洞高/m	顶板厚度/m	洞跨/m	洞体充填情况	数量
13.5~28.2	0.8~7.9	0.3~3.6	0.9~6.7	无充填，钻进掉钻、漏浆	42
13.2~31	1.0~13.5	0.2~5.2	0.7~9.2	半充填，流塑状粉质黏土	45
14.7~28.5	0.7~7.9	0.6~4.4	0.5~7.4	半充填，软塑—可塑状粉质黏土	27
15.0~32.7	0.8~11.6	0.1~4.9	1.0~11.7	全充填，可塑、软塑状粉质黏土	18

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表 2 岩土体的物理力学参数

Table 2. Physical and mechanical parameters of rock and soil mass

岩性	密度/kg•m⁻³	剪切模量/MPa	体积模量/MPa	弹性模量/MPa	泊松比	粘聚力/kPa	内摩擦角/°	抗拉强度/MPa
素填土	1 890	5.32	15.97	14.37	0.35	27.6	15.6	—
砾砂	1 940	11.11	33.33	30.00	0.35	0	34.0	—
粉质黏土	1 880	6.20	13.42	16.11	0.30	26.1	14.1	—
石灰岩	2 524	7 260.00	14 870.00	18 740.00	0.29	3 740.0	30.3	1.58
低标号混凝土	2 200	—	—	1 000.00	0.15	580.0	40.0	—
泡沫混凝土	910	—	—	310.00	0.20	120.0	8.0	—
自密实土	2 000	—	—	26.00	0.30	21.0	22.0	—

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