研究目的：既有运营盾构隧道上覆基坑开挖时面临近接施工问题,隧道的变形及稳定性控制要求严格。为探究近接施工保护措施的可行性及效果,结合某地铁出入口基坑开挖工程,采用有限元数值模拟的方式对加固措施进行分析,并提取关键特征点位移与实际监测数据进行对比,揭示上覆基坑开挖引起的隧道变形规律,提出针对性的设计关键要点。
研究结论：（1）上覆基坑开挖卸载诱发盾构隧道隆起的工程问题,在“时间”和“空间”上可以采用近接施工全过程措施进行变形及稳定性的有效控制;（2）上覆基坑采用旋喷桩竖向止水帷幕加MJS注浆水平封底的地下水控制措施,能够隔断水力联系,减小基坑降水对盾构隧道的影响;（3）充分利用基坑分段开挖中的时空效应,分段长度应结合基坑宽度、夹层土厚度综合考虑;（4）本研究成果可为周边环境控制严格的隧道及地下通道类工程案例提供借鉴和参考。
Abstract
Research purposes: The excavation of the overlying foundation pit of the existing operating shield tunnel is faced with the problem of adjacent construction, and the deformation and stability control requirements of the tunnel are strict. To explore the feasibility and effect of adjacent construction protection measures, combined with the foundation pit excavation project of a subway entrance, the reinforcement measures were analyzed by finite element numerical simulation, and the displacement of key feature points was extracted and compared with the actual monitoring data. The deformation law of the tunnel caused by the excavation of the overlying foundation pit was analyzed, and the key points of the targeted design were put forward.
Research conclusions: (1) Because of the engineering problem of shield tunnel uplift induced by excavation and unloading of overlying foundation pit, the whole process of close construction can be used to effectively control the deformation and stability in ‘time’ and ‘space’. (2)The overlying foundation pit adopts the groundwater control measures of a vertical waterproof curtain of jet grouting pile and MJS grouting horizontal bottom sealing, which can cut off the hydraulic connection and reduce the influence of foundation pit dewatering on the shield tunnel. (3) Full attention should be paid to the space-time effect in the excavation of the foundation pit, and the length of the section should be considered in combination with the width of the foundation pit and the thickness of the interlayer soil. (4)The research results can provide a reference for tunnel and underground channel engineering cases with strict surrounding environment control.
关键词
盾构隧道 /
近接施工 /
上覆基坑 /
变形控制设计
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Key words
shield tunnel /
proximity construction /
overlying foundation pit /
deformation control design
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中图分类号：
U455
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参考文献
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Chen Huan.Key Technology of Foundation Pit Construction above Shield Tunnel[J]. Modern Urban Transit, 2022(7): 60-65.
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脚注
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基金
国家重点研发计划项目 (2019YFC0605104,2023YFC3009304); 中铁建科研项目（2022-B02）
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