Taking the Zhouwancun tunnel along Xuanji railway crossing the water-rich fault as the case,we applied the FLAC 3D fi-nite difference software to carry out multi-field coupling calculation which is based on the Biot consolidation dynamic coupling equa-tion,in order to study the dynamic response of the cross-fault tunnel under seepage-earthquake coupling.The influence of the width of the fault fracture zone on the acceleration,pore pressure,displacement and stress response law of the tunnel lining characteristic point is mainly analyzed.The results show that the existence of the fault fracture zone causes the peak acceleration at the arch foot to increase by 30.8％compared with the ordinary segment,and the peak acceleration at the vault increases by 11.4％compared with the ordinary segment.Under the action of the coupling field,the principal stress at the interface between the tunnel and the fault fracture zone under-goes an obvious mutation,and the range of the stress mutation expands with the increase of the fault width.As the fault width increases,the pore pressure and principal stress peaks also further expand.By adding a grouting layer,the phenomenon of uneven stress distribu-tion of the arch ring caused by the action of the coupling field can be effectively reduced.
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