Force Characteristics of Longitudinal Joints of Shield Tunnel under Seismic Action

The longitudinal joints of shield tunnels are the weak parts of the structure when bearing loads and deformations in practical engineering. A numerical analysis method which analyzes from the whole to the local was put forward based on the mechanical characteristics of the longitudinal joints under seismic action. According to the equivalent longitudinal stiffness beam theory, the 3D time-history analysis model of stratum-structure was established to obtain the extreme value of structural longitudinal internal force, the extreme value was then taken as the external load which was applied on the entire 3D analysis model of the whole ring to obtain the boundary force of the most unfavorable region of shield tunnels. The mechanical characteristics of the longitudinal joints were analyzed by applying the boundary force to the local refined model of the longitudinal joints. The method was discussed by an integrated corridor project specifically. The results show that the shield tunnels mainly suffer cyclic horizontal bending in the longitudinal direction when it is under the transverse seismic excitation, the cyclic vertical bending and longitudinal tension of the tunnel are notable when the seismic wave is excited longitudinally. The local area with the largest longitudinal opening is always under tension whether subjected to axial tension or longitudinal horizontal bending moment, which means that the influence of these two working conditions on the force pattern of the local area are essentially the same. When the local area with the largest longitudinal opening is under tension, the maximum tensile stress area is located at the hand hole on the inside of the segment, and the maximum compressive stress area is distributed around the bolt hole in a ring shape.