盾构穿越多条既有隧道施工环境扰动分析

新建盾构穿越多条既有隧道施工是近年不断出现的新型地下空间布置形式。穿越邻近既有隧道过程除了会使地表发生隆沉,还会对已有隧道产生扰动变形影响。建立了针对新建盾构垂直上、下穿现有隧道穿越施工形式的三维弹塑性有限元动力学模型,并进行了全过程仿真分析。并根据一些结果,提出了预测多线盾构隧道施工地表沉降的Peck修正公式。研究表明:当各隧道间的净距处于扰动影响范围内时,盾构掘进对地层产生二次扰动,将对既有隧道产生较大影响。盾构上穿现有隧道时,地面将发生较大变形,且均呈隆起趋势;而下穿现有隧道时,地面将发生较小的变形,现有隧道均呈下沉趋势。研究成果可为工程实际施工建设提供理论支持。

Analysis of environmental disturbance in shield tunneling across several existing tunnels

The construction of new shield crossing several existing tunnels is a new type of underground space layout in recent years. The process of crossing the existing tunnel, which make the ground surface sink, but also affect the deformation of the existing tunnel. For two kinds of typical construction methods of up-crossing and under-crossing, the 3D elastoplastic FEM was applied to analysis the dynamic construction process. A modified Peck equation was proposed to predict ground settlement according to some results. The results showed that when interval among all tunnels are in the influenced range, a secondary disturbance is caused by shield advance and greater influence will be made on the existing tunnels. During the construction of up-crossing, ground settlement turns to be larger, the existing tunnels have a tendency of upward moving. Whereas the under-crossing makes a smaller settlement with a tendency of subsidence. This research provides some theoretical basis and prophase guidance for practical engineering construction.