Numerical Analysis Of Transverse Seismic Response Of Tunnel Subjected To Asynchronous Seismic Excitation

The study on asynchronous seismic response of tunnel structure is an important issue of the seismic study of tunnel structure at present.The thorough and comprehensive study on the seismic response of tunnel subjected to the asynchronous seismic wave is the premise of the seismic design,earthquake-reduction design and seismic performance evaluation of tunnel structure.In this work,a numerical method for calculating the transverse asynchronous seismic response of underground structures is introduced and verified,then applied to study the transverse seismic response of a lined circular tunnel in layered foundation and a lined horseshoe tunnel across fault fracture zone subjected to the asynchronous seismic waves.Furthermore,by conducting asynchronous seismic time history analysis of three typical cross-sections of the large-span transition part in the direction of Zhangjiakou,the seismic performance of the Badaling Tunnel of Beijing-Zhangjiakou high-speed railway is evaluated.The main study results are as follows:(1)The transverse dynamic response charateristics of lined circular tunnel subjected to asynchronous seismic waves is revealed: the dynamic response charateristics of circular tunnel under asynchronous seismic excitation is significantly different from that of synchronous seismic excitation,and the former is often more unfavorable;the dynamic response of circular tunnel excited by SV wave is greater than that by P wave for the same seismic wave with the same incident angle.In addition,the dynamic response charateristics of tunnel subjected to asynchronous earthquake is affected by buried depth,diameter,soil-structure stiffness ratio,etc.Compared with the uniform foundation,the dynamic response of the tunnel located in the non-uniform foundation is greater,and the distribution characteristics is quite different;the dynamic response of the tunnel is the most unfavorable when it is located at the stratum interface of the layered foundation.(2)The transverse asynchronous seismic response characteristics of the tunnel across the avtive fault fracture zone is revealed: the deformation amplification effect due to its low stiffness,the displacement and acceleration response difference caused by its discontinuity,and relative acceleration or displacement caused by the slip of fault fracture zone are the main reasons of the earthquake failure for tunnel across the fault fracture zone.The asynchronous seismic response of the tunnel across the fault fracture zone is affected by factors like the incident angle of the seismic wave,the dip angle of the fault and fault slip friction coefficient.The earthquake-reduction effect of the thickness of grouting material and rubber buffer layer on the tunnel structure across the fault fracture zone is studied quantitatively as well.(3)Taking Badaling Tunnel of Beijing-Zhangjiakou High-speed Railway as the engineering background,three typical cross-sections in the transition part crossing the fault fracture zone are selected to carry out the time history analysis on the asynchronous seismic response.The numerical result is analyzed by referring to the two seismic deformation evaluation indexes(Diameter Deformation Rate and Interlayer Displacement Angle)for underground structures recommended by relevant codes.It is found that tunnel seismic deformation of all three selected sections is within the allowable range,and the triple-arch section(especially its middle wall)is the key section/part of seismic fortification or earthquake-reduction design.