人工填土层中四连拱暗挖隧道设计

人工填土层有土质疏松、稳定性差、无法形成自然应力拱等特点,导致隧道暗挖修建时易出现支护体系受力较大、地面沉降过大甚至塌方等问题。以北京地铁某停车线工程在人工填土层中修建暗挖四连拱隧道为例,采用理论分析结合有限元数值仿真模拟,从支护体系受力、地面沉降、风险控制、施工工期等方面对"导洞法"、"侧洞法"及两者相结合的"导洞+侧洞法"进行比选,得出采用"侧洞法"施工为本工程最优方案。"侧洞法"能有效避免中隔墙的水平位移问题,控制沉降较好,且二次衬砌能尽早封闭成环,减小初期支护受力过大的风险,并在施工中取得成功。

Case Study on Design of Mined 4-arched Tunnel in Artificially-filled Soil Strata

Due to the loose and instable property of artificially filled soil strata, it is difficult to build mined tunnels in such strata. In the paper, the design of a 4 arched tunnel of Beijing Metro located in artificially filled soil strata is studied by means of theoretical analysis and finite element numerical simulation. Comparison and contrast is made among three construction methods, i.e., pilot method, side heading method and “pilot method + side heading method”, in terms of stress on the support structure, ground surface settlement, risk control and construction period. Conclusion is drawn that the side heading method is the optimum construction method for the project. The proposed method has been adopted for the project, which shows that the method can minimize the horizontal displacement of the central wall, bring the settlement under effective control, make the secondary lining form a closed ring as early as possible and reduce the stress on the primary support.