基于MIDAS的地铁隧道开挖对邻近建筑物的变形影响分析

MIDAS-based Analysis of Deformation Effect of Subway Tunnel Excavation on Adjacent Buildings

地铁隧道规划往往会经过城市的繁华地段,不可避免的对邻近既有建筑物造成影响,如何有效控制地铁开挖过程中引起的建筑物变形沉降问题一直是研究的重难点。以南京地铁7号线为例,采用MIDAS数值模拟软件建立三维地质模型,首先分析地铁隧道开挖对既有建筑物的影响,后依次对三台阶法和交叉中隔墙(CRD)法开挖引起围岩变形进行研究,最后对隧道完工后的监测点曲线进行变形分析。结果表明:地铁隧道开挖穿越邻近建筑物这一过程,离隧道近的建筑物基础点沉降量很大,而离隧道远的建筑物基础点沉降量相对较小,由沉降差可知为不均匀性沉降;相比于CRD法,采用三台阶开挖法能有效降低隧道开挖处的拱顶沉降,提高隧道围岩的安全稳定性。由于隧道开挖导致围岩应力迅速释放以及初期支护效果的滞后性,相比于隧道周边收敛点变形而言,拱顶处的变形幅度则更大。

The planning of subway tunnel often passes through the hustle and bustle area of the city,which inevitably affects the adjacent existing buildings.How to effectively control the deformation and settlement of buildings caused by subway excavation has always been a difficult problem in research.In this paper,Nanjing Metro Line 7 is taken as an example.MIDAS numerical simulation software is used to establish a three-dimensional geological model.Firstly,the influence of subway tunnel excavation on the existing buildings is analyzed,and then the surrounding rock deformation caused by three-step method and CRD method is studied.The results show that the settlement of the foundation points near the tunnel direction is large,while the settlement of the foundation points far from the tunnel direction is relatively small.The settlement difference shows that the settlement is nonuniform.Compared with the CRD method,the three-step excavation method can effectively reduce the settlement of the vault and improve the safety and stability of tunnel surrounding rock.Due to the rapid release of surrounding rock stress caused by tunnel excavation and the lag of initial support effect,the deformation range at the vault is larger than that at the convergence point around the tunnel.