Earthquake-Resistant Numeric Analysis Of Immersed Tunnels

Because of its advantages in traversing the channels, with the development of the national economy, immersed tunnels will inevitably be used as the main means of traversing rivers, bays and seabeds. In the cities divided by rivers over bays, immersed tunnels have great superiorities in connecting the different parts. However, immersed tunnels are generally build in soft soil shallowly and affected greatly by the earthquake. In view of its importance and underwater particularity, the destruction of immersed tunnels will be disastrous. Accordingly, it is necessary to carry out earthquake-resistant research of immersed tunnels. Currently, researchers from home and abroad usually use simplified models in the aseismatic analyses of immersed tunnels, which can not properly simulate the two functions of the soil, while the finite element method solves this problem successfully, and the development of numeric calculation and computer technology lays a solid basis for its application, it is a pity that the applications of FEM is not common currently. In this paper taking Nanjing Changjiang Immersed Tunnel as an example, the author made a research of aseismatic analyses of immersed tunnels by introducing FEM, and also, made a further discussion of factors such as depth, geologic conditions, water and boundary conditions. Analytic results indicate that the calculation results with simple boundaries is larger than those with viscous boundaries, that it is adequate that the transverse calculation range is taken as six times of the diameter of the tunnel with simple boundaries, that it is accurate enough to analyze the transverse seismic response with planar models, that the seismic response of immersed tunnels increases with the increasement of depth and it is great in hard rock , and that the coupling of water and structures has a little influence on the seismic response of immersed tunnels. The conclusions of this paper can be used as a reference in earthquake-resistant design and analyses of immersed tunnels.