地铁盾构双隧道施工诱发的地层变形规律分析

Analysis of Stratum Deformation Rules Induced by the Construction of Double-Tube Parallel Shield Tunnels for Metro

以大连地铁202标段双隧道盾构施工工程为背景,考虑土体的分层以及隧道施工过程中盾构推进、注浆和衬砌拼装等工序,运用FLAC3D软件对盾构双隧道同向先后施工过程进行三维精细数值模拟,并与现场测量数据进行对比分析。结果表明:先施工的右线隧道掘进完成后,隧道上方各层土体越靠近地表,盾构施工引起的地层竖向变形越小,而地层的沉降槽宽度越大,地表沉降槽宽度系数为0.56;近距离双隧道同向先后开挖时,土体相互扰动,地层距离隧道轴线的高度越小,地层竖向变形非对称"双峰"特征越明显,岩层的成层性使得双峰特征消失时岩层距离隧道轴线的高度有差别;两隧道中心线和轴线附近地表有不同方向水平变形,此区域的桩基、剪力墙在隧道掘进时将受到附加剪切作用,易出现裂缝,故在施工中应做好切实的防护措施;监测结果验证了数值模拟方法的正确性,在盾构掌子面距离监测点12m范围内,地表沉降发展得较快。

With No. 202 bid section of Dalian Metro double-tube parallel shield tunneling as engineering background, considering the layers of soil mass as well as the process of tunnel construction, shield driv- ing, grouting and lining assembling, the successive construction process of double-tube parallel shield tun- nels in the same direction was simulated with FLAC3D and the simulated results were compared with in-situ values. Results show that, after the completion of the right line tunnel driving, the soil layers above tun- nel are closer to the surface, the vertical deformation caused by shield construction is smaller. The width of ground settlement trough is bigger. The width parameter of ground settlement trough is 0.56. When short-distance double tunnels are successively excavated, mutual disturbance occurs in soil mass. The characteristics of asymmetrical ＂two-peak＂ of the vertical stratum deformation are more obvious when the distance between the soil layer and tunnel axis is shorter. The distances between rock strata and tunnel ax- is are different when the characteristics of two peaks disappear owing to the layered property of rock stra- ta. There is horizontal displacement of different directions on the surface near both sides of center line and the axis of two tunnels. The pile foundation and shear wall within this range will bear additional shear ac- tion during tunnel driving, and is liable to crack. Therefore, protective measures should be considered in construction. Monitoring results have validated the correctness of the numerical simulation method. Ground settlement develops rapidly within the range of 12 m from shield tunnel face to monitoring point.