Analysis Of Dynamic Response Of Shield Tunnel Under Strong Earthquake

The construction of rail transit is inseparable from the construction of tunnels.As an important method of tunnel construction,shield tunnel is broadly used in tunnel project.China is situated between the Pacific Rim Seismic Belt and the Eurasian Seismic Belt.The seismic fault zone is very active due to the compression of the Pacific Plate,the Indian Plate and the Philippine Plate.Therefore,research on seismic performance and seismic design of tunnel engineering is an important problem that needs to be solved urgently.The research in this paper takes the Shanghai Yangtze River Shield Tunnel as the background,and studies the dynamic response assessment of the shield tunnel under strong earthquakes,which can provide a reference for the seismic design of the shield tunnel.This article mainly carried out the following work:Consult relevant information to understand the research status of tunnel dynamic response under earthquake action at home and abroad,master the seismic analysis method of underground structure and the dynamic response characteristics of underground structure.Through the Duncan Zhang model,equivalent linear model,dynamic artificial boundary,proportional boundary finite element method and other theories,a three-dimensional numerical model of the shield tunnel structure is established.By coMParing the dynamic response of tunnels with different lengths such as displacement,velocity,acceleration,axial stress,principal and minor stress,and dynamic shear stress,a more suitable tunnel length is selected to carry out the next research work.A single variable method was used to research the dynamic reaction of the tunnel under different thickness of overlying soil layer,different crest value of seismic wave,and different incident angle of seismic wave.The study found that the peak of the horizontal displacement of the arch shoulder is the smallest,the peak of the horizontal displacement of the arch foot is the largest,the axial stress of the left arch shoulder is the largest,and the tensile stress appears at the arch foot.According to the numerical calculation results in this paper,it can be found that with the increase of the buried depth,the peak of the horizontal displacement of the tunnel gradually decreases,and the peak of the vertical displacement gradually decreases and tends to be stable;with the increase of the buried depth,the peak of dynamic shear stress first increases After the reduction,the maximum axial stress peak moves from the arch shoulder to the arch foot.As the angle of incidence increases,the positive peak of the horizontal displacement first decreases and then increases,and the negative peak first increases and then decreases;with the increase of the incident angle,the peak of the main principal stress gradually moves from the arch foot to the arch waist.As the peak acceleration of the seismic wave increases,the dynamic response of the earthquake becomes more obvious.The dynamic shear stress at the left arch waist is the largest.When it exceeds the allowable shear stress of 1.75 MPa,the tunnel is prone to shear failure.