地铁盾构双线隧道施工地层变形及衬砌结构应力数值分析

Numerical Analysis of Lining Structure Stress and Ground Settlement Induced by Double-Tube Parallel Shield Tunneling

为预测盾构双隧道施工周围土体的变形及衬砌结构管片应力规律,以石家庄地铁1号线07标段北宋—谈固站区间双线隧道为工程背景,在考虑各土层材料性质及盾构施工工艺的基础上,利用FLAC3D建立了盾构双隧道的三维精细数值模型,研究了盾构双隧道衬砌管片的应力规律,并与现场实际监测数据进行了对比分析.结果表明:盾构隧道开挖造成的地层沉降大致沿隧道轴线与水平线夹角45°向地表扩散.横向地表沉降的影响距离距隧道中心约为30m.随着隧道埋深增加,对应地表监测点位累计沉降值变小,与隧道埋深成反比对应关系.隧道附近土体的第一主应力存在应力集中现象,应力集中系数约为1.3.衬砌管片应力分布存在差异性,靠近双隧道共同扰动的管片侧的拉应力和剪切应力集中现象较为明显.衬砌管片横断面形变以"椭圆化"变形为主,兼有断面收缩变形.

In order to analyze the surrounding soil structure in the shield tunneling process and the stress and deformation law of lining structure, the dynamic simulation of the shield tunneling is conducted with Flac3D software combining with the engineering situation of Shi Jiazhuang double parallel tunnels line No. 1-07. The stress and deformation of surrounding soil and lining for double-shield tunnel construction are studied, and the simulated results are compared with in-situ values. It is shown that the ground subsidence caused by shield tunnel excavation is spread to the surface along the tunnel axis, and the horizontal diffusion angle is about 45 o. The influence range of the horizontal ground surface settlement is about 40 m distance from the center of the tunnel. The corresponding accumulated subsidence value of the surface monitoring pointsn is decreased with the increase of buried depth. The tunnel buried depth is inversely proportional to the corresponding relationship. There is stress concentration phenomenon in soil around the tunnel. The stress concentration coefficient is about 1.3. The stress distribution of cross section of lining segment exists difference. The concentration phenomenon of the tensile stress and shear stress is more obvious near common disturbance zone of double tunnels. The main deformation of cross section of lining segment is ovalization deformation and shrinkage deformation.