兰州地铁1号线下穿既有地下通道的影响分析

Analysis on Inf luence of Lanzhou Metro Line No.1 Undercrossing an Existing Underground Passage

采用有限差分软件FLAC3D建立三维数值模型,模拟了兰州地铁1号线盾构隧道在砂卵石地层中下穿既有地下通道的施工过程,对比分析基底预加固和未加固2种工况下下穿施工对地下通道的影响和地基沉降变形情况,并且进一步分析了未加固时自由场地、已有地下通道2种场地条件下施工引起的地下通道基底变形情况。结果表明:基底预加固可使地下通道不均匀变形及整体沉降明显减小;地下通道的存在有提高地层整体刚度、抵御部分沉降变形的能力。工程实践表明,预加固有效控制了最大沉降量、最大沉降差和地层变形范围;地下通道变形均小于规范限值,整体稳定性良好。

A tunnel construction using shield method was simulated with FLAC.This tunnel is part of Lanzhou metro Line No.1,and it is undercross an existing underground passage in gravels and sandstones.With this threedimensional model,the influence of the construction on the existing underground passage and the settlement were analyzed,considering two cases.One is that the foundation is prereinforced and the other is the opposite.Also,for the second case,the settlements of the free field and the existing underground passage due to construction were analyzed.The results show that the existence of the underground passage has improved the integral stiffness and decreased the settlement and deformation.The pre-reinforcement effectively controls the maximum settlement and the maximum settlement difference,and the stratum settlement range.The deformation of the underground passage is within the allowable value,indicating integral stability.