平行双基坑同步开挖引起邻近地铁盾构隧道变形监测分析
刘凤华
Monitoring and Analysis of the Adjacent Metro Shield Tunnel Deformation Caused by Simultaneous Excavation of Parallel Double Foundation Pits
LIU Fenghua
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作者信息:上海隧道工程有限公司， 200082， 上海
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Affiliation:Shanghai Tunnel Engineering Co., Ltd.， 200082， 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.2024.03.009
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中图分类号/CLCN:TU433
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栏目/Col:研究报告
摘要:
［目的］双基坑同步开挖会对邻近地铁盾构隧道造成影响。为了保障邻近盾构隧道的稳定性，需对平行双基坑同步开挖引起的邻近盾构隧道的变形规律进行监测分析。［方法］以杭州地铁6号线江汉路站为工程背景，基于隧道竖向位移、水平位移及收敛变形等现场监测数据，分析平行双基坑同步开挖对邻近盾构隧道的影响，探究施工风险节点。［结果及结论］基坑长边效应及其卸载应力集中导致基坑中部的隧道水平位移较两侧都大，先开挖区土体的扰动随着后开挖基坑的施工逐步叠加，使得隧道最大水平位移发生在基坑的后开挖区；隧道竖向位移曲线由于双基坑同步开挖、架设支撑、浇筑坑底，而形成两处波峰、一处波谷的特征；在邻近基坑偏心卸载作用下，隧道横截面收敛变形呈横鸭蛋形；双基坑平行于盾构隧道同步开挖，产生叠加效应，进一步加剧隧道的变形发展；基坑分区、分层的开挖方式能较好地利用时空效应，减少基坑的暴露时间，有效限制坑底土体的回弹，大大减小土体的隆起。合理采取分区分层、限时开挖，及时架设支撑，以及浇筑钢筋混凝土基础底板等措施，可以有效减小双基坑开挖对邻近盾构隧道的影响。
Abstracts:
［Objective］ Simultaneous excavation of double foundation pits will affect the adjacent metro shield tunnel. In order to ensure the stability of the adjacent shield tunnel, it is necessary to monitor and analyze the deformation law of the above tunnel caused by simultaneous excavation of parallel double foundation pits. ［Method］ With Jianghan Road Station of Hangzhou Metro Line 6 as the engineering background, based on the on-site monitoring data of tunnel vertical displacement, horizontal displacement and convergence deformation, the effect of the simultaneous excavation of parallel double foundation pits on the adjacent shield tunnel is analyzed, and the construction risk nodes are explored. ［Result & Conclusion］ The long side effect of foundation pit and the concentration of unloading stress cause a larger horizontal displacement of the tunnel in the middle of the foundation pit than that on both sides of the pit. The disturbance of the soil in the early excavation area gradually superimposes with the construction of the later excavation foundation pit. As a result, the maximum horizontal displacement of the tunnel occurs in the later excavation area. The vertical displacement curve of the tunnel is characterized by two peaks and one trough due to the simultaneous excavation, erection support and pouring of the pit bottom. With the effect of eccentric unloading of the adjacent foundation pit, the convergence deformation of tunnel cross-section turns into a traverse duck egg-like shape. The simultaneous excavation of the double foundation pits paralleling to the shield tunnel produces superposition effect, and further aggravates the deformation development of the tunnel. The partitioned and layered excavation method can make good use of time and space, reduce the exposure time of foundation pit, effectively limit the rebound of soil at the bottom of the pit, thus greatly reduce the uplift of soil. Reasonable measures such as partitioning and layering, time-limited excavation, timely erection of support, and pouring reinforced concrete foundation plate can effectively reduce the influence of double foundation pit excavation on the adjacent shield tunnel.
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