盾构超近距离上穿诱发既有隧道纵向与水平变形研究

Research on Longitudinal and Horizontal Deformation of Existing Tunnel Induced by Shield Tunneling in Extra Close Distance

盾构超近距离上穿既有运营隧道时,由于施工引起的土体扰动较大,控制地层沉降和扰动变形的难度也随之增大。基于宁波轨道交通5号线上穿运营的宁波轨道交通2号线区间隧道建立Flac^(3D)模型,研究了掘进过程中既有隧道的变形规律,并探究了不同推进速度对隧道变形的影响。结果表明,当隧道开挖时,在掌子面还未达到既有隧道范围、位于既有隧道中心附近、超出既有隧道范围的过程中,既有隧道的纵向沉降与水平位移均出现明显的上升与回落现象;隧道超近距离上穿既有隧道将诱发双线隧道上行线和下行线相似的竖向沉降以及不同的水平变形规律,且水平变形数值沿盾构掘进方向有所增大;在保障隧道施工过程稳定性的前提下,考虑工程特点与施工效率,试验段推进12环/d,穿越段推进10环/d为该工程的最佳推进速度。

When the shield passes through the existing operating tunnel from above with extra close distance,the soil disturbance caused by construction is large,so it is difficult to control the ground settlement and the structure disturbance deformation.Based on the section tunnel of Ningbo Metro Line 5 passing through the existing operating Ningbo Metro Line 2 from above,this paper established a three-dimensional finite element numerical analysis model,studied the deformation law of the existing tunnel in the tunneling process,and analyzed the influence of different propulsion speed on tunnel deformation.The results showed that the longitudinal settlement and horizontal displacement of the existing tunnel rose and fell obviously due to the excavation disturbance in the process of the face not reaching the scope of the existing tunnel,near the center of the existing tunnel and beyond the scope of the existing tunnel.The similar vertical settlement and different horizontal displacement of the uplink and downlink would be induced when the shield passing through the existing tunnel from above with extra close distance,and the horizontal displacement value would increase along the direction of shield tunneling.On the premise of ensuring the stability of the tunneling process,considering the engineering characteristics and construction efficiency,the best advancing speed of the project was 12 rings per day for the test section and 10 rings per day for the crossing section .