Study On The Influence Of Peak Ground Motion Parameters On Dynamic Response Of Tunnels

China is located in the junction of the Pacific tectonic belt and the Himalaya tectonic zone.The subduction of the Pacific plate and the collision of the India plate northward to the Asian plate make the continent of China bear the most important dynamic action of the earth,and the seismic fault zone is very active.With the rapid development of the national economy,more and more long tunnels are developing into the West.Many long tunnels under construction or in the West are inevitably built in high intensity areas or through active faults.Ground motion is the important cause of structural failure of long tunnel structure.Therefore,the research of ground motion characteristics has a far-reaching impact on the seismic development of underground structures.Base on the explicit finite element method and the time-domain wave analysis method combined with the viscous-spring artificial boundary,a hybrid simulation method is adopted to generate four groups artificial ground motions,for discovering the influence of peak ground velocity(PGV),peak ground displacement(PGD)and peak ground acceleration(PGA).The infulence mechanism of the peak factor is analyzed by the integral response deformation method.The main work and conclusions of this paper are listed as follows:(1)According to the standard design response spectrum,two groups of artifical ground motions have the same peak value in acceleration and displacement but different velocities were selected for discussing the peak ground velocity on the seismic respose of the long tunnel.The results show that when the P wave and SV wave are obliquely incident along the longitudinal section,the hoop tensile strain,the longitudinal tension strain and the longitudinal tension have obvious PGV amplification effect,and when the P wave and SV wave are obliquely inclined along the cross section,the hoop tensile strain and the longitudinal tension have obvious PGV amplification effect.(2)According to the standard design response spectrum,two groups of artifical ground motions have the same peak value in acceleration and velocity but different displacements were selected for discussing the peak ground displacement on the seismic respose of the long tunnel.The results show that when the P wave and SV wave are obliquely incident along the longitudinal section,only the hoop tensile strain have obvious PGD amplification effect on the vault and arch bottom of the tunnel,and when the P wave and SV wave are obliquely inclined along the cross section,the variation of the longitudinal force compoent and the cross section strain compoent is not obvious.(3)According to the standard design response spectrum,two groups of artifical ground motions have the same peak value in velocity and displacement but different accelerations were selected for discussing the peak ground acceleration on the seismic respose of the long tunnel.The results show that when the P wave and SV wave are obliquely incident along the longitudinal section and along the cross section,there are different PGA amplification effects on the longitudinal force compoent and the cross section strain compoent.(4)The integral response deformation method(IRDM)is applied to calculate and analyze the calculated results with the dynamic time history method,in order to explain the mechanism of the peak velocity action.The results shows that the PGV amplication effect of the longitudinal tensionF_x,the hoop tensile strainε_h,the longitudinal tension strainε_a is mainly caused by the deformation of the soil layers,and the shear effect around the structure will not produce the obvious PGV amplication effect when the P wave is obliquely incident along the axial section.