Abstract：
As the longitudinal stiffness of shield tunnels is less than that of transverse sections, it is likely to suffer from seismic damage caused by excessive deformation, especially at places where the ground or the structure changes suddenly, and so the longitudinal aseismic study is worthy of attention. Based on the ground-structure mode, this paper uses a longitudinal equivalent stiffness model to simulate the longitudinal dynamic response of shield tunnels under different seismic actions and to verify the aseismic indicators of the longitudinal rotation angle, segment and joint bolt stress. The results show that: the areas with abrupt changes between hard and soft ground are the weakest parts of shield tunnels regarding the longitudinal aseismic design, and the areas where the internal forces of the tunnel structure increase obviously at the soft ground side are four times the areas covered by the tunnel external diameter; when the seismic wave spreads in a lateral direction, the longitudinal moment plays a control role, and when the
seismic wave is input vertically, the higher axial force plays the control role; and the tunnel structure is in a more unfavorable condition with longitudinal seismic excitation as compared to lateral excitation under the same level of
seismic action.
2016, Vol. 53 