基坑开挖对近接既有地铁隧道的影响分析

Analysis on Influence of Foundation Pit Excavation on Adjacent Existing Subway Tunnels

目的研究深大基坑开挖对近接既有隧道及周围土体的影响.方法以杭州某邻近地铁隧道的基坑工程为例,采用PLAXIS对基坑开挖进行数值模拟分析.结果基坑开挖会引起邻近既有隧道和周围土体的扰动,但扰动程度较小,地表沉降与隧道变形均在设计要求范围之内;地表沉降、隧道位移会随坑底水平边界尺寸的增大而增大;基坑平面开挖形状改变会影响隧道位移的变化趋势,平面开挖形状越规则,隧道位移变化曲线越平滑;地表沉降槽的形状不受坑内水平边界尺寸和平面开挖形状改变的影响,验证了地表沉降槽曲线的形状与隧道地表沉降形态变化系数C有相关性.结论使用数值分析方法研究基坑与隧道的近接工程时,必须考虑基坑的开挖方式及有限元模型的尺寸.

In order to study the influence of deep foundation pit excavation on the adjacent existing tunnel and surrounding soil,a 2-D FE model was established based on the practice of deep excavation adjacent to the subway tunnel in Hangzhou by the finite element software PLAXIS.The results indicate that the influence of foundation excavation on the adjacent subway shield zone is small,and the surface settlement and displacement of values linings are in the limited range.The surface settlement and tunnel displacement increase with the increase of the horizontal boundary size.The change trend of tunnel displacement is affected by the plane excavation shape of foundation pit.The more regular the plane excavation shape is,the smoother the curve of tunnel displacement change will be.The shape of the surface settlement trough is not affected by the size of the horizontal boundary in the pit and the shape of the plane excavation.The shape of the surface subsidence trough is not affected by the horizontal boundary size and the shape of the plane excavation in the pit.It verified that the shape of the surface subsidence curve is related to the variation coefficient of the tunnel surface settlement.The method of excavation and the size of finite element model must be considered when using numerical analysis method to study the close engineering of foundation pit and tunnel.