小曲线半径盾构隧道上穿既有隧道影响分析

为研究新建盾构隧道上穿既有隧道时对下部隧道影响,以南昌某地铁出入线上穿既有盾构隧道工程为依托,结合小曲线半径隧道、盾构机超载等特殊工况,采用有限元进行模拟分析。研究结果表明:盾构机超载将导致既有隧道纵向呈凹槽型沉降变形,最大值约-9.7 mm,管片弯矩值较未开挖时增长34.3%;上部开挖卸载将导致既有隧道纵向呈隆起变形,最大值约8.7 mm,管片弯矩值较未开挖时略有减小;既有隧道在盾构机超载及开挖卸载两者耦合作用下,纵向变形呈“S”型曲线,最大隆起值与最大沉降值差值高达13.8 mm。针对上述分析,提出对既有隧道施加钢支撑环+拱顶注浆的加固措施,隧道最大变形值较未加固时减小44.8%,验证了该加固措施的有效性,对小曲线半径段施工控制重难点进行分析,并提出相应建议,以期为相关工程提供参考依据。

Impact Analysis of Small Curve Radius Shield Tunnel crossing Existing Tunnel

In order to study the impact of the new shield tunnel on the lower tunnel when passing through the existing tunnel, based on the subway tunnel passing through the existing shield tunnel project in Nanchang, combined with the special working conditions of small curve radius tunnel and overload of shield machine, it is adopted Finite element simulation analysis. The results of the study indicate that overloading of the shield machine will cause the existing tunnel to have longitudinal groove-shaped settlement deformation, the maximum value is about -9.7 mm, and the bending moment value of the segment increases by 34.3% compared with the unexcavated; Longitudinal uplift deformation, the maximum value is about 8.7 mm, and the bending moment value of the segment is slightly reduced compared with that without excavation; the longitudinal deformation of the existing tunnel is “S” under the coupling effect of overload of shield machine and excavation and unloading type curve, the difference between the maximum uplift value and the maximum settlement value is up to 13.8mm. In view of the above analysis, the reinforcement measures for the existing tunnel with steel support ring and vault grouting are proposed. The maximum deformation value of the tunnel is reduced by 44.8% compared with the unreinforced. Analysis the major and difficult points of control provides reference for related projects.