Research Of Seismic Dynamic Response Of Submarine Tunnel

With the development of the transportation demand,the construction of submarine tunnels is being promotted hotly.But the submarine tunnel is constructed at the bottom of the sea as special type of underground structures,and it is in a very complaticated engineering geological and hydrogeological environment,there are a lot of uncertain factors such as fault fracture and crushed zone,which make it hard to repair after the construction of submarine tunnels,thus the consequences of the damage induced by an earthquake are incalculable.Therefore,the study on the dynamic response of submarine tunnels under seismic excitation seems to be particularly important.This paper forcus on transverse vibration response of the submarine tunnel under seismic excitation,mainly consisting of two parts: one part is the theoretical theoretical derivation analysis,the other part is the numerical simulation analysis.During the process of theoretical derivation,the most common free vibration equation of the beam including the following factors such as internal damping,external damping,axial force,shear deformation,rotational inertia is first derived on the base of elastic theory,the theory of structural dynamics and soil-structure interaction theory,and the degradation analysis aimed at the equation is carried on.Then in view of the submarine tunnel characteristics of high water pressure,the vibration equation and forced vibration equation of submarine tunnels with consideration of the influence of water pressure are derived based on Winkler's foundation model.Using the method of variable separation,the vibration mode and natural vibration frequencies of submarine tunnels are obtained.And the expression of structural displacement and the interaction coefficient between the soil and submarine tunnel are also determined.Numerical example is given and the effects of water pressure on structural natural vibration frequencies,structural displacement and interaction coefficient are also studied.In the numerical simulation part,using the finite difference software Flac3 d,the three-dimensional calculation model of the submarine tunnel is built and the dynamic reponse characteristics of the submarine tunnel under seismic excitation are researched.By comparing the theoretical derivation results and numerical simulation results,the influence law of water pressure on natural frequencies and vertical vibration displacement is verified.And the influence of water pressure on the stress state of tunnel structures under seismic excitation is also researched by the analysis of the stress time history curve.