Study On Seismic Dynamic Response Of Cheyang Tunnel In Ya'lu Expressway

The response and safety of underground structures under earthquake are among the most difficult and essential problems to be solved for construction engineering in the intensive earthquake areas of West China. The seismic response analysis of underground structures is of great economic and social significance. In this thesis, combined with the project of aseismic and vibration absorption of tunnel in YA'LU expressway, the responses of tunnel portal and tunnel body are numerically analyzed by using FLAC^3D, and the influential factors such as depth of burial, space between the tunnel, geological conditions and liner stiffness are studied comprehensively. The main contents of this thesis are as follows:Firstly, the seismic wave selection and dealing method are discussed. The method to deal with the man-made seismic wave is proposed; the spectrum or frequency components are analyzed by FFT and time-frequency method, for numerical precision and stability, the high frequency part in seismic wave have been filtered by the low-pass filter device; due to the baseline drift in the seismic wave, baseline correction based on the least squares method have been applied. Then, the precision of the common artificial boundary has been analyzed by numerical analysis.Secondly, the seismic dynamic responses of the tunnel portal and body have been analyzed. The uneven pressure portal and common portal are analyzed separately, and the results have been compared; the worst position of the liner has been found and the safety analysis is accordingly carried out based on the results. Furthermore, comparison is made between the seismic responses of the tunnel portal and body. The effects of shock absorption are analyzed by grouting the surrounding rock.Thirdly, the seismic dynamic responses of tunnel under different conditions have been discussed. The effects of many factors on seismic dynamic response of tunnel, such as depth of burial, distance of the two tunnels, parameters of surrounding rock, lining stiffness, are numerical modeled, and rules of variation in corresponding parameters are analyzed. The seismic dynamic responses of tunnel are analyzed by using different earthquake wave travel orientation and multidimensional wave, the results have been compared between the multidimensional wave and one-dimensional wave.In the final chapter of this thesis, conclusion and expectation are given.