双层初支软岩大跨车站下穿高层建筑安全研究

Study on Safety of Double-Layer Primary Support Soft Rock Large-Span Subway Station Underpass Tall Building

摘要: 针对软岩地区大跨暗挖车站开挖容易出现大变形问题，本文依托重庆地铁18号线某地铁车站工程，使用有限元分析软件Midas GTS NX建立三维地层–结构模型，分析了在双层初支结构下，软岩地区大跨车站开挖隧道的拱顶沉降、双层初支应力分布以及地表建筑物沉降随施工阶段的变化。结果显示：双层初支成环后能有效控制拱顶沉降，拱顶沉降增长最快时间为双层初支成环前一开挖步；二次初支的承担比例小于一次初支，具体比例可能与开挖进尺和隧道埋深有关；当隧道开挖区域与建筑物的距离较远时，建筑物会随土体发生向上的位移，建筑物越高，这个距离越短。

Abstract: To solve the problem of large deformation in the excavation of large-span stations in soft rock area, this paper relied on the project of the Xietaizi Station of Chongqing Metro Line 18 and used the finite element analysis software Midas GTS NX to establish a three-dimensional stratiform-structure model. Changes of arch crown settlement, double-layer primary support initial stress distribution and surface building settlement with construction phase of tunnel excavation at large-span station in soft rock area. The results show that the arch crown settlement can be controlled effectively after the double-layer primary support is formed, and the arch settlement increases fastest at the first excavation step before the double-layer initial support is ring closed. The proportion of secondary primary support is smaller than that of initial primary support, and the specific proportion may be related to the excavation footage and the depth of tunnel. When the distance between the tunnel excavation area and the building is far away, the building will move upward with the soil mass. The higher the building is, the shorter the distance will be.