钢板桩围护基坑开挖对下卧地铁隧道影响的数值模拟研究
韩宇峰1徐前卫1黄通2贺翔1段罗2杨革2郭玉坤3
Impact Numerical Simulation of Steel Sheet Pile Foundation Pit Excavation on Underlying Metro Tunnels
HAN Yufeng1XU Qianwei1HUANG Tong2HE Xiang1DUAN Luo2YANG Ge2GUO Yukun3
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作者信息:1.同济大学道路与交通工程教育部重点实验室， 201804， 上海
2.中国中铁二局第五工程有限公司， 610031， 成都
3.中国铁路上海局集团有限公司上海东站铁路建设项目管理部， 200071， 上海
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Affiliation:1.Key Laboratory of Road and Transportation Engineering of the Ministry of Education, Tongji University, 201804, Shanghai, China
2.China Railway ERJU No.5 Engineering Co., Ltd., 610031, Chengdu, China
3.Shanghai East Railway Station Project Management Department, China Railway Shanghai Group Co., Ltd., 200071, Shanghai, China
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关键词:
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Key words:
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DOI:10.16037/j.1007-869x.20245958
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中图分类号/CLCN:U455.4;TU94+1
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栏目/Col:土建工程
摘要:
［目的］在既有地铁隧道上方施工深基坑将引起隧道变形，采用钢板桩围护垂直开挖施工,可减少单段开挖覆土量，有利于控制隧道上浮，应对钢板桩围护垂直开挖对下卧地铁隧道的变形影响进行深入研究。［方法］依托某地铁隧道工程，采用数值模拟方法,建立了钢板桩围护基坑的二维和三维有限元模型，分别模拟了基坑降水工况及不同开挖步骤条件。通过线性回归分析，讨论了降水对下卧隧道沉降和水平位移的影响情况。通过校验模型结果与实测值，讨论了土方开挖对下卧隧道沉降和水平位移的影响情况。结合现场监测结果验证模型可靠性后，进一步预测了采用钢板桩围护条件下隧道的上浮变形。［结果及结论］钢板桩围护垂直开挖可有效控制隧道变形；下卧隧道拱顶处的沉降峰值较拱腰处更大，且变化幅度也更大；利用监测数据拟合获得的隧道沉降降水影响折减系数为0.05~0.30，在覆土越多的区域，该经验折减系数更趋向于较大值;水平位移不受降水影响,不需要折减；修正结果后预测在钢板桩围护垂直开挖区段内，东线和西线隧道拱顶上浮分别约为3.3~5.7 mm和4.5~6.6 mm。
Abstracts:
［Objective］ Deep foundation pit excavation above existing metro tunnels may cause tunnel deformation. Vertical excavation with steel sheet pile support can reduce the amount of overburden soil removed from each segment, which is conducive to help control the tunnel uplift. It is required to conduct an in-depth analysis of the deformation effects of vertical excavation with steel sheet pile support on underlying metro tunnels. ［Method］ Based on a metro tunnel engineering, using numerical simulation method, two-dimensional and three-dimensional finite element models of a foundation pit retained by steel sheet piles are established, to simulate the dewatering conditions of the foundation pit and the conditions of different excavation steps separately. Then, through linear regression analysis, the impact of earthwork excavation on the settlement and horizontal displacement of the underlying tunnel is discussed. Through the verification model results and field-measured results, the influence of soil excavation on underlying tunnel settlement and horizontal displacement is discussed. After verifying model reliability with field-monitored data, tunnel uplift deformation under steel sheet pile support conditions is further predicted. ［Result & Conclusion］ Vertical excavation with steel sheet pile support can effectively control tunnel deformation. The peak settlement at underlying tunnel vault is greater and exhibits larger variation than that at arch waist, and the variation amplitude is bigger; the reduction coefficient for tunnel settlement dewatering impact obtained from monitoring data fitting is 0.05 to 0.30. In areas with greater overburden soil, the empirical reduction coefficient tends to be higher; the horizontal displacement is not under dewatering impact and no reduction is needed. It is predicted that after correction, in the steel sheet pile excavation section, the tunnel vault uplifts on east-line and west-line are approximately 3.3 to 5.7 mm and 4.5 to 6.6 mm, respectively.
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