Study On Transverse Dynamic Response Of Shield Tunnel Under High Water Pressure

Shield tunnel has become a popular form of tunnels for the underground transportation at present because of its good sesmic safety and high construction efficiency.Compared with the ground building,the history of seismic study of the shield tunnel is short and the experience is not enough,and the seismic theories have evolved from the seismic theory of the ground building.Because the shield tunnel is mostly built underground and is confined by soil,it is generally believed that the shield tunnel has strong seismic resistance and did not got enough attention.However,the great earthquake,represented by the Kobe and Wenchuan earthquakes,has sounded the alarm for the us,and the shield tunnel has been seriously damaged in these earthquakes.Through the summary of these engineering disasters,people have a new understanding of the dynamic response of the shield tunnel.But there remain many problems unsolved.This paper focuses on some unsolved problems.Considering that the shield tunnel is a bolt-connected structure,the distribution of stiffness of the tunnel is inhomogeneous.The dynamic response characteristics of the shield tunnel are studied by the discrete beam-spring model.The studied problems and obtained results are summarized as follows:(1)Firstly,the dynamic response of shield tunnel subjected to axial shear wave propagation is studied.A beam-spring model is established to simulate the interaction between soil and structure.The shear action between the shield segments and the inhomogeneity of the longitudinal stiffness of the shield tunnel are considered,and a discrete analysis model of the shield tunnel is established,and the multi degree of freedom motion equation of the shield tunnel under the action of simple harmonic waves is derived.By using the center difference method,the iterative equation of motion of the tunnel is obtained,and the software MATLAB is used to calculate the emporal-spatial characteristics of the dynamic response of the tunnel under seismic action,and the influence of the shear stiffness between the shield segments on the lateral dynamic response of the shield tunnel is determined.(2)The influence of foundation stiffness change on the dynamic response of shield tunnel is studied.The dynamic equilibrium equation of tunnel with consideration of stiffness change is develpoed,.The central difference method is used to obtain the discrete dynamic equilibrium equation of the whole tunnel.Dynamic response of shield tunnel under the seismic action are obtained by using the MATLAB.In the example,the influence of the change of mechanical parameters on the two sides of the earth-rock interface on the shield tunnel dynamic response is obtained,and the maximum shear force and the maximum joint slide are determined.(3)The problem of the effect of high water pressure on dynamic response of cross-ocean tunnel is studied.Based on the previous theoretical studies and joint model tests,it is found that the increase of water pressure will increase the shear stiffness of tunnel joints.Based on this conclusion,this paper studied the effect of high water pressure on dynamic response of the shield tunnel,and reached the conclusion that the high water pressure is favorable to the transverse earthquake resistance of the shield tunnel.