基于颗粒流的覆盖型岩溶地面塌陷动态演化特征研究

师海; 贾智磊; 白明洲; 张晔; 孙子冰

doi:10.11932/karst20240509

基于颗粒流的覆盖型岩溶地面塌陷动态演化特征研究

doi: 10.11932/karst20240509

师海^{1, 2,},
贾智磊^1,,
白明洲^{1, 3},
张晔¹,
孙子冰¹

1.
北京交通大学土木建筑工程学院, 北京 100044
2.
轨道工程北京市重点实验室, 北京 100044
3.
北京市轨道交通线路安全与防灾工程技术研究中心, 北京 100044

基金项目: 国家自然科学基金项目（41907260、42172311）；中央引导地方科技发展资金项目（216Z3802G)

详细信息

作者简介:
师海（1987－），男，博士，副教授，主要从事岩溶灾害防治和地面塌陷领域的教学科研工作。E-mail：shihai@bjtu.edu.cn

中图分类号: P642.5
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出版历程
- 收稿日期: 2022-10-07
- 录用日期: 2023-05-02
- 修回日期: 2023-03-30
- 网络出版日期: 2024-12-30
- 刊出日期: 2024-10-25

Dynamic evolution characteristics of ground collapse of covered karst based on particle flow

SHI Hai^{1, 2
,},
JIA Zhilei^1
,,
BAI Mingzhou^{1, 3},
ZHANG Ye¹,
SUN Zibing¹

1.
School of Civil Engineering, Beijing Jiaotong University, Beijing100044, China
2.
Beijing Key Laboratory of Track Engineering, Beijing 100044, China
3.
Beijing Engineering and Technology Research Center of Rail Transit Line Safety and Disaster Prevention, Beijing 100044, China

摘要

摘要: 为揭示铁路周边覆盖型岩溶土洞扩展的动态演化规律和细观致塌机理，以京沪高铁（江西段）某典型岩溶塌陷点为依托，通过颗粒流（PFC^2D）压缩试验对塌陷土体的强度参数进行标定，引入接触黏结模型，建立覆盖型岩溶地面塌陷流固耦合模型，从细观角度揭示了岩溶地面塌陷的动态演化过程与变形特征，探究不同溶洞开口大小、覆盖层厚度、地下水位高度对覆盖型岩溶地面塌陷变形特征的影响。研究表明：地表沉降、土体孔隙率等随塌陷演化发展而逐渐增大；地下水位高度越高，土洞扩展越快，地表沉降越明显，塌陷也越易发生；溶洞开口越大，地面沉降深度和范围随之增大，塌陷越易发生；覆盖层厚度越小，地表沉降变化越明显；从细观角度可知，塌陷过程中颗粒间接触力变化过程近似为“应力平衡－应力拱形成－应力拱破坏－应力再次平衡－…－应力拱断裂”的规律。研究从细观角度揭示了岩溶地面塌陷演化的全过程，可为高速铁路建设、运营期周围环境覆盖型岩溶地面塌陷的防灾减灾提供参考。
- 覆盖型岩溶 /
- 土洞扩展 /
- 颗粒流 /
- 数值模拟 /
- 动态演化
Abstract: Karst collapse represents a significant geological hazard, predominantly occurring in regions characterized by the presence of soluble rock formations, including carbonate rocks, calcareous clastic rocks and salt rocks, among others. The characteristics of karst collapse fall into three key attributes: a hidden spatial distribution, a sudden occurrence and a periodic recurrence over time. These attributes can collectively challenge the construction of major infrastructure in karst areas. A karst collapse disaster along the railway will potentially pose a significant threat to the safe construction and continued operation of the high-speed railways. During both the construction and operational phases of railways in karst areas, pumping and discharging groundwater, along with altering hydrodynamic conditions, have been identified as key factors contributing to karst collapse. The most widely used numerical simulation method is the finite element method (FEM), which is based on the assumption of a continuous medium. FEM simplifies a complex problem by breaking it down into more manageable components. It conceptualizes the solution domain as a collection of small interconnected sub-domains called finite elements. For each element, a suitable (simpler) approximate solution is assumed, and the conditions necessary for solving the overall domain are derived. However, soil is not a continuous medium; therefore, a model based on FEM is unable to simulate the local instability of a collapsed soil body, the damage process at a mesoscopic scale, and other phenomena. In light of the dearth of sufficient attention to the temporal effects and fine-scale mechanisms of the karst collapse process in current studies, this paper aims to elucidate the dynamic evolution laws and mesoscopic-scale collapse mechanisms of the expansion of overlying karst soil caves around the railway.A typical karst collapse site, namely the Beijing–Shanghai high-speed railway (Jiangxi section), was selected as the basis for calibrating the strength parameters of the collapsed soil body. This was achieved through a particle flow (PFC^2D) compression test, in which a contact bonding model was also introduced. This model assumed that the filler in the cave was entirely washed away due to the erosive effect of groundwater seepage. Additionally, the vacuum suction and erosion effect inside the cave were not taken into consideration during the simulation period. The effect of groundwater on soil strength was simulated by reducing the contact strength between particles below the modelled water level. In conclusion, a coupled flow-solid model of overlying karst collapse has been established, which can elucidate the dynamic evolution process and deformation characteristics of karst collapse from a mesoscopic view. Furthermore, the influence of various sizes of cave openings, thicknesses of overburden layers and groundwater levels on the deformation of the overlying karst collapse has been investigated. The migration laws of soil particles under the influence of different factors have been analyzed.The study demonstrates that during the evolution of overlying karst collapse, the contact force between particles undergoes a series of changes, which can be described approximately as follows: equilibrium of stress–formation of stress arch–destruction of stress arch–equilibrium of stress again–…– fracture of stress arch. The internal stress of the soil body demonstrates the following pattern: compressive stress gradually decreasing, tensile stress gradually increasing, and tensile stress disappearing. Additionally, the surface subsidence and porosity of the soil body tend to increase in conjunction with the collapse evolution process. It can be observed that the larger the opening of the cave is, the greater the depth and range of surface subsidence become, which in turn increases the likelihood of collapse. A reduction in the thickness of an overburden layer may cause a more pronounced surface subsidence, thereby increasing the likelihood of collapse. Similarly, an elevated water level may contribute to a more rapid expansion of the soil cave, which in turn will cause a more pronounced surface subsidence and an increased propensity for collapse. The relationship between surface subsidence and thickness of overburden layer is not significant when the thickness of the latter is large. The study provides a comprehensive account of the karst collapse evolution from a mesoscopic perspective, offering insights into prevention and mitigation of karst collapse during the construction and operation of high-speed railways.
- covered karst /
- expansion of soil cave /
- particle flow /
- numerical simulation /
- dynamic evolution

HTML

图 1 研究区岩溶地貌

Figure 1. Karst landform of the study area

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图 2 潜在塌陷区地层结构剖面图

Figure 2. Profile of the stratigraphic structure of potential collapse area

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图 3 双轴试验模型

Figure 3. Biaxial test model

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图 4 模拟的不同围压下应力-应变曲线

Figure 4. Simulated stress-strain curves under different confining pressures

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图 5 数值计算模型

Figure 5. Numerical model

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图 6 流固耦合管域模型

Figure 6. Model of pipes and domains for fluid-solid coupling

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图 7 塌陷全过程模拟

Figure 7. Simulated collapse process

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图 8 地表竖向位移变化

Figure 8. Vertical displacement of the surface

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图 9 不同测点处孔隙率随塌陷进程变化规律

Figure 9. Variation of porosity at different monitoring points with collapse process

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图 10 不同测点塌陷土体内部竖向应力变化曲线

Figure 10. Curve of variation in internal vertical stress of collapsing soil at different monitoring points

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图 11 不同溶洞开口大小条件下地表沉降变化

Figure 11. Variation of vertical surface displacement under different opening sizes of caves

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图 12 不同覆盖层厚度条件下地表沉降变化

Figure 12. Variation of vertical surface displacement under different overburden thicknesses

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图 13 不同水位高度条件下地表沉降变化

Figure 13. Variation of vertical surface displacement under different water levels

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图 14 不同水位高度突变条件土洞塌陷临界高度

Figure 14. Critical heights of collapsing soil caves under different water levels

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表 1 颗粒流固耦合主要模型参数

Table 1. Main model parameters of particle fluid-solid coupling

岩土层类型	埋深	法向刚度/ MPa·m⁻³	法向-切线刚度比	粘聚力/ kPa	内摩擦角/ °	摩擦系数	容重/ g·cm⁻³	孔隙率/ %
回填土（残坡积粉质黏土）	0−0.5 m	38	1.5	20.5	28.7	0.3	1.68	33
残坡积层粉质黏土	0.5−1.5 m	34	1.5	22.28	25.06	0.3	1.68	32
坡洪积层粉质黏土	1.5−2.5 m	34	1.5	32.54	38.71	0.3	1.69	32
灰岩	>2.5 m	38	1.5	25.47	20	0.3	1.88	28

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