软土地区大面积基坑施工对临近运营地铁区间隧道的影响分析

Analysis of the influence of large-area foundation pit construction in soft soil area on the adjacent operating subway tunnel

随着城市建设的快速发展,地铁区间隧道周围建筑物逐渐往密集、高层和复杂化方向发展,新建的大量深基坑工程都位于运营区间隧道影响范围内,不可避免的会使得隧道结构产生附加变形。本文结合昆明OCC基坑工程实例,根据两者之间的相对位置关系,判定外部工程作业影响等级,并提出变形控制标准以及确保地铁安全的工程措施。采用ANSYS有限元软件进行数值模拟研究,分别对基坑整体开挖和采用分期施工、优化基坑深度、增加连续墙插入深度等措施开挖的情况进行模拟,对比分析隧道周围土体的位移场分布情况,研究基坑施工对运营地铁区间隧道的影响,判断其安全性。对计算结果进行分析发现,采用保护措施后隧道结构最大位移均小于变形控制值,相较于整体开挖有较大优化,说明采取分期施工等措施可以保证既有隧道结构安全,对类似工程有借鉴作用。

With the rapid development of urban construction,the buildings around the subway interval tunnels are gradually developing towards the direction of denseness,high-rise and complexity.A large number of new deep foundation pit projects are located within the influence range of the operating interval tunnels,which will inevitably cause additional deformation of the tunnel structure.Combined with the example of Kunming OCC foundation pit project,according to the position relationship between plane and section,this paper determines the impact level of external operations,and proposes deformation control standards and corresponding engineering measures.The ANSYS finite element software is used to conduct numerical simulation research.The overall excavation of the foundation pit and the excavation of the foundation pit with staged construction,optimization of the depth of the foundation pit,increase of the insertion depth of the diaphragm wall and other measures are simulated respectively.The distribution of the displacement field of the soil around the tunnel is compared and analyzed.The impact of the foundation pit construction on the operation of the subway interval tunnel is studied to judge its safety.The analysis of the calculation results shows that the maximum displacement of the tunnel structure after the protection measures are adopted is less than the deformation control value,which is greatly optimized compared with the overall excavation.It shows that the phased construction and other measures can ensure the safety of the existing tunnel structure,which is a reference for similar projects.