Experimental Study And Numerical Analysis On Seismic Responses Of Immersed Tunnel

Along with the rapid development of economic integration,cities are more closely connected.Urban underground transit system safety has been increasingly expanding constructed,especially immersed tunnel system.Immersed tunnels are always built under water with soft soil layer,in case of damage,the consequences will be inconceivable.However,immersed tunnels cost a lot and need long duration.So,it seems urgent to study the seismic performance of immersed tunnels.For seismic research of immersed tunnels,model test and numerical simulation are two necessary methods.To study the seismic behavior of immersed tunnels at different sites and the enhancement of mechanics performance of tunnel joints is the purpose.Mechanism and anti-earthquake design of immersed tunnel is the difficulty.This paper introduces the shaking-table tests of immersed tunnels under diverse site conditions and the cycle loading quasi-static tests of immersed tunnel joints,and the researches were made as follows:1.Shaking-table tests of immersed tunnels at unsaturated and saturated sand sitesShaking-table tests on seismic performance of immersed tunnels at unsaturated and saturated sand sites were carried out,then the acceleration and spectrum of soil layer,pore pressure,immersed tunnel acceleration and dynamic structure strain of five groups of tests were analyzed.It verifies that site liquefaction,earthquake input direction,water layer and flexible tunnel joint influence the seismic behavior of immersed tunnel model.2.3-Dimensional finite element static analysis of immersed tunnel jointNonlinear static finite element analysis on immersed tunnel joint responses under shear force was executed by ABAQUS,and shear keys reaction mechanism of immersed tunnel was analyzed,then it provides a reference for quasi-static testing design of immersed tunnel joint.Then shock absorption steel panels were introduced into anti-seismic design of immersed tunnel joint.Q235 steel panel finite element model was established by ABAQUS,then plastic deformation capacity of Q235 steel panel was studied.3.Quasi-static testing of integrated immersed tunnel jointCycle quasi-static testing of an integrated immersed tunnel model with two tunnel tubes was carried out.Then hysteretic behavior of tunnel joint,structural strain,structural bearing capacity,stiffness,and ductility were analyzed.Finally,earthquake performance and mechanical mechanism of integrated immersed tunnel were studied.4.Quasi-static testing of partial immersed tunnel joint under different axial forceThrough a series of cycle quasi-static tests of partial immersed tunnel joints under axial force 300 KN,600KN,and 800 KN,then hysteretic behavior,strain,bearingcapacity,and stiffness of shear key were obtained.A comparison of these four groups of tests was analyzed.5.Quasi-static testing of energy dissipation immersed tunnel jointRectangle and arc-shaped Q235 steel panel with 6mm and 10 mm in thickness were designed for energy dissipation of immersed tunnel joint.According to four groups of quasi-static tests of immersed tunnel joint with Q235 steel dampers,seismic behavior of immersed tunnel joint was studied,meanwhile,it also indicates that utilization of energy dissipation devices can be realized in anti-seismic design of immersed tunnel.