Seismic performance of tunnel lining of side-by-side and vertically stacked twin-tunnels

The dynamic interaction between tunnel lining and its surrounding soil is a complicated issue as the magnitude of seismic wave from bedrock to the structure can be easily influenced by the geometrical layout and structural stiffness of the tunnel. A series of numerical analysis was conducted to study the dynamic response of the tunnel lining of side-by-side and vertically stacked double-tube tunnel since the inertia and kinematic interactions between the tunnel lining and the surrounding soil during an earthquake could induce excessive stresses to the lining itself due to the stiffness variation between the lining and the soil. Real earthquake ground acceleration was used as an input motion in the dynamic analysis. The interactive behavior of bending moment and axial forces, and the displacement of the tunnels were used to evaluate the effect of tunnel geometrical layout on the performance of the lining. It is found that the effect of earthquake on the axial thrust of the lining is insignificant, and there is a reduction of the bending moment in the lining due to the redistribution of the surrounding soil after the earthquake.