Numerical Analysis On Behavior Of Immersed Tunnel Under Seismic Shaking

As the immersed tunnel shows its superiority in the river-crossing and the sea-crossing transportation engineering, it has been the main type in the underwater tunneling engineering. Immersed tunnels are built under the riverbed or seabed, mostly in a shallow position in the bedrock, thus they have several particularities the same to the underground structures. So it is not a negligible issue to research the immersed tunnels’ reaction under seismic shaking. In this paper, several research has been done as follows:Firstly, the development history of the immersed tunnel and its research status are reviewed with the main achievement concluded. Combined with the research status of the underground structures, this paper studies the working mechanism of seismic shaking and the underground structures’ response characteristics. In addition, the classic research methods of immersed tunnel under seismic shaking are discussed.Secondly, the dynamic finite element method as a numerical analysis method in anti- seismic study is described in detail and some problems as the choice of soil constitutive model and the dynamic artificial boundary and the adjustment of the seismic shaking are discussed. Combined with the practical engineering- the Fenjiang Road South Extension Tunnel for subway and highway in Foshan city, then consider its asymmetry and the surrounding soil distribution characteristics, the two-dimensional simulation model and the three-dimensional simulation model of immersed tunnel-soil are built by using computer dynamic finite analysis software technology.Thirdly, by calculating the two-dimensional and three-dimensional simulation models under seismic shaking, the responses of the practical engineering are studied in both transverse and longitudinal orientation, thus obtains the time-history results of the stress, displacement and acceleration of the key parts of immersed tunnel structure.Furthermore, several different simulation models are built, they have different back silting properties, different action direction of seismic wave and different acceleration peak value of seismic wave. By calculating the dynamic response under different simulation models, the behaviors of the immersed tunnel are comparatively analyzed, and finally obtains the dynamic response rules of immersed tunnel under seismic shaking.