Seismic Analysis of Shallow Tunnel in Bad Ground with the Numerical Simulation Method
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Guo Zihong, Luo Ruyue, Li Tangyong, Zou Gaoqiang, Gong Han, He Jialin
Seismic damages of the tunnel show that surrounding rock of shallow tunnel is mostly of a low grade and its stability is poor. The shallow tunnel is susceptible to earthquake. The dynamic calculation of the shallow tunnel in bad ground is performed by establishing a two-dimensional numerical model and using viscoelastic artificial boundary to simulate the dynamic boundary. Acceleration distribution in surrounding rock, the inner force variation of lining structure and the seismic displacement of surrounding rock are all analysed. The results show that the acceleration of surrounding rock increases with the decrease of the distance from the ground surface. The acceleration at ground surface is about 1.5 times at vault of tunnel and the acceleration of surrounding rock is gradually reduced from the tunnel structure to the model boundary. The horizontal displacement of surrounding rock keeps decreasing when its location moves away from the tunnel, and the displacement at each point increases with the shaking time and shaking intensity. Under seismic loading, the axial force and bending moment change most obviously at spandrel and arch foot of tunnel where the lining structure should be strengthened.
Shallow tunnel, numerical simulation, seismic analysis, bad ground