基坑施工对运营地铁隧道的变形影响及控制研究

Influence of deep excavation on deformation of operating metro tunnels and countermeasures

以上海某邻近地铁隧道的基坑工程为背景,运用FLAC-3D软件建立三维数值分析模型,对基坑施工进行全过程动态模拟。结果表明:计算结果与工程监测数据基本吻合,邻近地铁隧道单侧基坑开挖可引起隧道结构的不对称变形。为保护邻近隧道,提出并采用了坑外二次加固的施工新工艺,首次指出地基加固体和地下结构物作为异质体对邻近基坑开挖产生的位移传递具有阻断作用。并对不同的施工方案进行数值模拟,对比分析表明,对紧贴基坑地下连续墙的土体进行二次加固及结构逆筑施工,可有效控制相邻隧道变形。

According to the practice of deep excavation adjacent to the subway tunnel in Shanghai,the software FLAC-3D is employed to establish a numerical model to simulate the whole dynamic process of the deep excavation.The calculated results show good agreement with the field measurements.The two results show that deep excavation adjacent to the operating metro tunnel at its one side induces uneven deformation.In order to protect the adjacent existing tunnel,a construction technology of the two-time reinforcement outside the deep excavation is brought forward and adopted.Underground obstacle as the barrier against the displacement transfer induced by deep excavation is presented for the first time.Different construction methods are simulated by the numerical method.The results indicate that the two-time reinforcement outside the deep excavation and the reversed construction method can effectively control the deformation of the metro tunnel.