泥质粉砂岩地层双连拱隧道开挖工法研究

Construction Method of Double-Arch Tunnel Excavation in Argillaceous Siltstone Strata

双连拱隧道可减小隧道线间距,空间利用率高,有效地节省工程投资,但存在施工工序复杂、围岩易受扰动、施工难度大、工期较长等特点;如何优化施工工序、控制围岩变形、确保施工质量是当前双连拱隧道设计和施工的重与难点。长沙市轨道交通5号线一期工程毛竹塘站存车线双联拱隧道工程,设计采用“五导洞+台阶法开挖”,该工法可连续施工作业,有效缩短工期,从而降低造价。为探讨该工法开挖对初支结构受力和地面沉降的影响,通过数值模拟分析与现场实测验证了该工法的可行性和安全性,可为同类型工程提供参考。

The double-arch tunnel has the advantages of reducing the spacing between two tunnels, having high space utilization rate, and effectively saving the investment cost, but there are disadvantages such as complicated construction process, potentially disturbance of the surrounding rock, difficult to construct, and long construction schedule. How to optimize the construction sequence, to control the deformation of the surrounding rock, and to ensure the construction quality are the current challenges in the design and construction of double-arch tunnels. This paper presents a case history of a double arch tunnel project of Maozhutang Station Storage Line of Changsha Rail Transit Line 5. The design utilized “five-pilot hole + stepped excavation” method, which could continuously perform the construct operations, effectively shorten the construction period, and thus reduce the construction cost. To explore the influence of the excavation on the stress and ground subsidence of the initial shielded structure, the feasibility and safety of the proposed method are validated by the numerical analysis and the on-site construction monitoring data. This information can provide a reference for the similar projects in the future.