Nonlinear Behavior Of Reinforced Concrete Circular Tunnel Under Seismic Motions In Clayey Soil

In this paper, nonlinear response of reinforced concrete circular tunnels subjected to seismic loads in clayey soil is presented. A series of two dimensional finite element models were adopted to investigate the dynamic behavior of tunnel soil system. The influence of several parameters including ground motion intensity, soil type, tunnel depth and tunnel diameter on the tunnel response was computed. Firstly, 1D equivalent-linear viscoelastic analysis was conducted in the frequency domain to evaluate the profile of Rayleigh damping coefficients. Hence, these profiles were used in order to simulate the 2D fully coupled finite element adopting visco-elasto-plastic effective stress models for the soil. The dynamic behaviour of tunnel was presented in terms of internal forces induced in tunnel lining. The analyses indicated that in case of the stiff clay, the results of closed form solution were close enough to the 2D analysis and the earthquake effects are considerable when the tunnel is close to the bed rock. In case of medium clay deposits, the effects vary according to the tunnel dimensions. Furthermore, Soft clay soil yielded when it exposed to earthquakes of greater than 0.5g magnitude. Earthquakes of 0.25g magnitude have a slight effect on the circular tunnels located at any depth in clayey deposit, but if another time domain are used with the same beak ground acceleration value, different effects might appear.