深基坑开挖降水对邻近地铁隧道的影响

The Influence of Deep Foundation Excavation Pit and Dewatering on Adjacent Metro Tunnel

深基坑开挖降水引起周围土体沉降变形问题是基坑工程的重要研究内容。基于比奥固结理论,以邻近长沙地铁5号线区间隧道的某在建基坑为工程实例,采用修正摩尔库伦本构关系,利用有限元分析软件Midas GTS NX建立三维数值分析模型,进行基坑降水速度对邻近地铁区间隧道影响的敏感性分析、不同工况的施工阶段分析、应力渗流单向耦合分析、完全应力渗流耦合分析与实际监测结果的对比分析。研究结果表明:基坑降水速度增加引起基坑支护结构内力非线性增长;完全应力渗流耦合作用下基坑开挖引起周边地层的位移比应力渗流单向耦合分析结果更符合实际监测结果,该地铁隧道最大变形控制结果满足相关规范要求,分析结果可为类似工程提供参考。

The settlement of surrounding soils caused by deep foundation pit excavation and dewatering is an important research content of foundation pit engineering. Based on the Biot’s Consolidation Theory,a foundation pit under construction in the adjacent subway tunnel of Changsha Metro Line 5 was taken as an engineering example in the thesis.A three-dimensional numerical analysis model was established by using Midas GTS NX to reconstruct the modified Mohr-Coulomb constitutive relationship.The sensitivity of the precipitation velocity influencing on the adjacent subway tunnel and the construction stages on different conditions were analyzed at first.The unidirectional coupling analysis of the stress seepage and the coupling analysis of the complete stress seepage were carried out later.The actual monitoring results were comparatively analyzed in the end.The results showed that the accelerating precipitation velocity of the foundation pit led to the non-linear growth of the structure inner force under certain conditions.The results based on the coupling analysis of the complete stress seepage are more in line with the actual monitoring results than that of the unidirectional coupling analysis of the stress seepage.The maximum deformation control results of the subway tunnel met requirements of the relevant specifications.The analysis results can provide a reference for similar projects.