Nonlinear Dynamic Responses of Tunnels under Longitudinal Seismic Actions

During strong earthquakes, the surrounding shield tunnel soil may enter the non-linear regime. When the springs and the dampers are utilized to simulate the soil-structure interaction, nonlinear properties of equivalent springs must be considered in dynamic analysis. This paper derived the nonlinear motion equations of tunnel segments under longitudinal seismic action. The characteristics of the nonlinear response of the shield tunnel segments under longitudinal seismic actions were analyzed. The influences of seismic P-wave velocity in soil and the parameter of tunnel segment bolting stiffness on internal force and deformation under non-linear soil-structure interaction were investigated. The numerical results showed that, if soil-structure interface enters nonlinear stress regime, the relative displacement between tunnel structure and soil will increase. This may lead to the increase in internal forces of structures which will produce stress concentration in structures.