Seismic Response Analysis Of Submarine Tunnel In Rieing Section Crossing Soft And Hard Stratum

Because the submarine tunnel is not affected by the harsh weather at sea,it can guarantee all-weather traffic and has good structural durability,so it is being used as an option for more and more cross-sea projects.Different from the mountain tunnel,the main body of the submarine tunnel is generally buried in the submarine bedrock,and both ends are connected to the ground through the ascending section.The tunnels at both ends rise from the submarine bedrock with a certain gradient and pass through different types of stratum to reach the ground soil layer.Due to the large differences in the mechanical properties of the various layers,uneven displacement occurs under the action of earthquakes,which leads to uneven deformation of the tunnels passing through different stratum with the movement of the stratum.The tunnel structure has large stress concentration and is prone to damage.Therefore,it is necessary to analyze the structural response of the submarine tunnel under the action of earthquakes when crossing the soft and hard surrounding rock during the ascent.In this paper,ABAQUS finite element software is used to establish the numerical analysis model of tunnel section crossing soft and hard uneven surrounding rock.The response of tunnel structure is analyzed and verified by dynamic time history analysis method and quasi-static method respectively,and the response law of tunnel structure in this case is summarized.Specific research contents are as follows:(1)The tunnel is equivalent to a homogeneous concrete ring by the equivalent stiffness method.The concrete plastic damage constitutive model is established by the Concrete Structure Design Code combined with the energy equivalent principle,and the equivalent linear viscoelasticity of the surrounding rock suitable for dynamic analysis is established.The constitutive model determines the infinite element artificial boundary conditions and selects the ground motion.The numerical models of the two analytical methods are established respectively.(2)In order to study the structural response of the tunnel under the action of earthquakes,the dynamic time history analysis method is used to compare the stress,internal force and deformation degree of the structure of the tunnel in the surrounding rock between the homogeneous surrounding rock and the soft and hard boundary.The tunnel is deformed greatly in the soft rock,and the whole body is unevenly deformed,which leads to the obvious increase of the force and deformation of the tunnel in the soft rock and the interface.At the same time,the variation law of the structural response of the tunnel under different factors including ground motion amplitude,concrete strength and lining thickness is analyzed by the control variable method.(3)A static pushing method based on the improvement of the ground structure is summarized,which is more convenient than the time history analysis.Firstly,the onedimensional equivalent linearization software is used to solve the seismic response of the free-field,and then the displacement is applied as the equivalent seismic load.The seismic response of the tunnel considering the simulated excavation is analyzed,and the results obtained by the dynamic time-course method are analyzed.A comparative analysis was carried out to verify the feasibility of the method.