渗流条件下富水砂层盾构隧道开挖面临界支护压力计算分析
张跃明1钟久强2余金3涂万年4朱碧堂4,5
Calculation and Analysis of Critical Supporting Pressure for Shield Tunnel Excavation Face in Water-rich Sandy Stratum under Seepage Condition
ZHANG Yueming1ZHONG Jiuqiang2YU Jin3U Wannian4ZHU Bitang4,5
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作者信息:1.广州地铁设计研究院股份有限公司， 510010， 广州
2.浙江省交通规划设计研究院有限公司， 310031， 杭州
3.江西水利职业学院建筑工程系， 330013， 南昌
4.华东交通大学土木建筑学院， 330013， 南昌
5.江西省地下空间技术开发工程研究中心， 330013， 南昌
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Affiliation:1.Guangzhou Metro Design & Research Institute Co., Ltd., 510010, Guangzhou, China
2.Zhejiang Provincial Transportation Planning Design Co., Ltd., 310031, Hangzhou, China
3.Department of Architectural Engineering, Jiangxi Water Resources Institute, 330013, Nanchang, China
4.School of Civil Engineering and Architecture, East China Jiaotong University, 330013, Nanchang, China
5.Engineering Research & Development Centre for Underground Technology of Jiangxi Province, 330013, Nanchang, China
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关键词:
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Key words:
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DOI:10.16037/j.1007-869x.2024.02.019
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中图分类号/CLCN:U231.3; U455.43
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栏目/Col:研究报告
摘要:
［目的］富水砂层是地铁盾构隧道常见的掘进地层，在土舱内外水压差作用下会发生渗流。因此，有必要研究渗流条件下，富水砂层盾构隧道开挖面临界支护压力的准确计算方法。［方法］采用三维有限元上下限极限分析法和Optum G3软件，对无渗流条件下的盾构隧道开挖面开展稳定性研究，通过主要参数敏感性分析，提出了不考虑渗流条件下的开挖面临界支护压力计算方法。考虑土舱内外水头差引起的渗流作用，采用三维有限元分析法和PLAXIS 3D软件，研究稳态渗流和流固耦合作用下富水砂层盾构隧道开挖面的失稳破坏模式。通过水头差、隧道埋深比和内摩擦角的敏感性分析，基于无渗流条件下的开挖面临界支护压力计算式，进一步提出了考虑稳态渗流条件下的开挖面临界支护压力计算方法。［结果及结论］所提计算式能够较为简便地确定富水砂层中盾构掘进的开挖面压力。对于不同的地下水状态，临界开挖面支护压力排序为：未发生渗流的临界开挖面支护压力＞发生渗流的临界开挖面支护压力＞干砂条件下的开挖面临界压力。当埋深比C/D<1、土体内摩擦角φ≤25°时，开挖面破坏区从拱底发展至接近地面处，容易发生浅层隧道冒顶破坏；当C/D≥1、φ>25°时，开挖面前方失稳破坏区局限于开挖面上方一定范围内，发生渗流时比无渗流时的破坏区域稍大。
Abstracts:
［Objective］ Water-rich sandy stratum is a common geological formation encountered in metro shield tunnel excavation. Seepage may occur under the influence of water pressure differences inside and outside the soil chamber. Therefore, it is essential to study the accurate calculation method for the critical supporting pressure on shield tunnel excavation face in water-rich sandy stratum under seepage condition. ［Method］ Using the 3D (three-dimensional) finite element upper and lower bound limit analysis method and Optum G3 software, stability studies are conducted on the shield excavation face under no-seepage condition. Through sensitivity analysis of key parameters, a calculation method for the excavation face critical supporting pressure without considering seepage condition is proposed. Considering the seepage action caused by the water level difference inside and outside the soil chamber, a 3D finite element analysis method and PLAXIS 3D software are employed to investigate the instability damage modes of shield excavation face in water-rich sandy stratum under steady-state seepage and fluid-soil coupling action. Through sensitivity analysis of water level difference, tunnel buried depth ratio, and internal friction angle, based on the calculation formula for excavation face critical supporting pressure without seepage, a calculation method for excavation face critical supporting pressure considering steady-state seepage condition is further proposed. ［Result & Conclusion］ The proposed formula allows for a relatively straight forward determination of the excavation face pressure during shield tunneling in water-rich sandy layers. For different groundwater conditions, the critical excavation face supporting pressure is ranked as follows: critical excavation face supporting pressure without seepage＞critical excavation face supporting pressure with seepage＞excavation face critical pressure under dry sand conditions. In the case of burial depth ratio C/D<1 and soil internal friction angle φ≤25°, the excavation face damage zone develops from the arch bottom to near the ground surface, making it susceptible to shallow tunnel roof collapses. While in the case of C/D≥1 and φ＞25°, the instability damage zone in front of the excavation face is limited to a certain range above the excavation face, with a slightly larger damage area when seepage occurs compared to situations without seepage.
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