Static And Dynamic Analysis Of River-Crossing Large Sectional Shield Tunnel

With the rapid developing of national economy in recent years, using the shield excavation method to build river-crossing tunnel has been widely used in urban construction.This paper’s main purpose is to analysis stress-strain results of large section crossing river shield tunnel under complex geological conditions, such as high water pressure. The paper established three-dimensional dimensional model with step-by-step excavation to simulate the actual project. To achieve the seismic dynamic analysis, the paper established two-dimensional geotechnical structure considering elastic-plastic geotechnical constitutive and damage constitutive of concrete. The mass-spring model considering changing foundation is established. And a beam element-spring model is established considering the segment assembly and structure model of bolt.The results showed that in the process of shield excavation excavation, displacement of surrounding rock and structure directly above and below the biggest; Shield tunneling in soft soil excavation needs large suface balance pressure to prevent the collapse.In two-dimensional dynamic time history analysis, the stress and displacement response of the tunnel structure is symmetric in left and right side. Arch’s spandrel and waist band is the largest, Arch’s above is the minimum.In two-dimensional horizontal quasi static and dynamic time history analysis, There will be a maximum compressive stress and plastic strain in the outside of the vault and the inner side of the arch shoulders as the weak position. There is fast-changing stress and displacement in the tunnel structure crossing the junction of the hard and soft soil layer. And there is larger plastic deformation in the outside of the tunnel structure which contacts with the surrounding rock. The soft soil layer has amplification effect to earthquake motion in longitudinal and transverse direction.