The Analysis Of Seismic Stability Of Cross-Ocean Tunnel Project Structure With Shock Absorption

It’s the dream of the people all over the world that linking the islands away from the land with the land by using the cross-ocean tunnel to improve the translation and promote the economic development. These dreams have been realized in many places along with the development of modern geological survey and the technology of engineering materials and construction.The cross-ocean tunnel has a more complex geological environment compared with other forms of tunnels such as land tunnel. There is complex geomorphology on the sea floor. The cross-ocean tunnel need to be excavated in the rock which below a certain depth of sea, whose depth is so great sometimes that the rock will withstand tremendous water pressure. The rock on the sea floor nearly are saturated fractured rock with weathered or slightly weathered where there is a high pore water pressure and seepage pressure because the geological conditions of the seabed are generally poor, where the weathered overburden is thicker. Therefore the cross-ocean tunnel more likely to appear unstable failure compared with land tunnel.The cross-ocean tunnel will play a decisive role in the future of the transportation along with the rapid development of economic and accelerated pace of people’s work and life. Therefore, there have important theoretical and practical significance of the project to study the seismic stability of the cross-ocean tunnel under complex geological environment and quantitatively estimate the safety factor.In the engineering background of Jiao Zhou Bay tunnel, the structure and fluid model were established by using ADINA software based on the existing study on seismic dynamic stability and static stability of tunnels. Considering the affect of the viscoelastic artificial boundary, earthquake and seepage, this thesis studied the affect of the sea depth, depth of the overburden and permeability coefficient to the safety factor of the cross-ocean tunnel and the law of changes of the plastic zone of the cross-ocean tunnel through fluid-structure interaction dynamic analysis of the two models. Also obtained the affect of setting shock absorption layer on the safety factor of the cross-ocean tunnel through the study on changes of the safety factor of the cross-ocean tunnel’s rock structure with shock absorption layer or not. The results showed that:(1) The plastic zone of the cross-ocean tunnel first appeared in the arch foot and the surrounding site of the spandrel on both sides of the arch under seepage and bidirectional earthquake, there are not plastic zone in the area of the vault which is safer. (2) The greater of the overburden’s depth is, the smaller of the safety factor is and more obviously the plastic zone developed when the sea depth is certain. The deeper of the sea depth is, the smaller of the safety factor is and more obviously the plastic zone developed when the overburden’s depth is certain, but the range ability is small. The permeability coefficient has little effect on the safety factor and the development of the plastic zone.(3) Setting shock absorption layer can elevate the safety factor of the cross-ocean tunnel structure under seismic action and have a good effect on damping.(4) The greater of the overburden’s depth is, the less of the advance of the safety factor of the cross-ocean tunnel structure under seismic action. Changes of the sea depth and permeability coefficient have little effect on the range ability of the safety factor due to the setting of the shock absorption layer.(5) Changes of the overburden’s depth have more effect on the safety factor of the cross-ocean tunnel structure under seismic action compared with the sea depth and permeability coefficient.