Numerical Analysis And Study On Seismic Response Of Shallow-Depth Tunnel

As the rapid development of tunnels and underground structures, the seismic response analysis of such structures is of great economic and social significance. In this thesis, the response of shallow-depth tunnels are numerically analyzed under seismic dynamic loading by finite difference method (FDM) in time-domain and some main points are studied. The contents in this thesis are concluded as follows:1. The numerical model of the infinite soil-structure dynamic interaction has been introduced to solve the seismic response. For time-domain numerical analysis of dynamic interaction, the basic governing dynamic equations in direct method are fully derived from the usual basic dynamic equations, and also the ones in substructure method are strictly formulated according to the dynamic force equilibrium and deformation compatibility on the structure-soil interfaces, which provides theoretical basis for the subsequent works in the dissertation.2. To present the strain-stress relation of soil under seismic dynamic loading, many soil dynamic constitutive models have been declared. The comparison between equivalent-linear method and fully nonlinear method is performed.3. Objective to time-domain method, wave motion signal for inputting needs to be made some treatments. First, FFT could indentifies the spectrum or frequency components in seismic signal. For numerical precision, then the part of high frequency which contain little wave energy may be filterd by means of filter devices. In the end, due to the effects of little long-period signal noises, baseline correction usually applies to adjust this shifting phenomenon.4. The numerical approachs for free-field seimic dynamic response have been performed using wave theroy. Nonlinear wave motion in layered soil are studied in detail.5. The computing precision of three type artificial boundaries such as viscous boundary, viscous-spring boundary and free-field boundary is compared. Base on various boundary conditions, the seismic response studies of a tunnel are executed. The influence of infinite foundation soil on the seismic response of the tunnel is researched and the weakness parts in liner are detenmined.6. The influences of ground water on tunnel seismic response are analyzed in detail based on undrained effective stress method. Finn model has been introduced to compare the tunnel dynamic response under two conditions such as including soil foundation liquefaction and not. Due to the effects of raising ground water level, the seismic response characters of foundation and tunnel are assessed.7. Numerical simulation is applied to solve the seismic dynamic response and demonstrate tunnel stability of the Shanghai metro. The analysis results under different dynamic loading by changing the wave input direction have been compared. In the end, tunnel construction effects on seismic response are performed.