Twin tunnel behavior under static and dynamic loads of Shiraz metro, Iran

Safety during construction and long-term stability of tunnels is among important factors in the design and implementation of underground spaces. Since tunnels and underground spaces are under dynamic loads such as earthquakes and explosions during construction and operation stages, dynamic stability analysis of such structures is of great importance. In this study, the twin tunnels of Shiraz subway were numerically modeled under static and dynamic loads with the help of Universal Distinct Element Code (UDEC). This is a finite element method (FEM) software, is any of a family of numerical methods. Unbalanced forces increase after tunnel excavation and applying static and dynamic loads. Although the increase in unbalanced forces was higher under dynamic loads, under static loads, velocity and displacement changes in the ceiling of the tunnel were higher than the rest of the tunnel. To apply a dynamic load, a sine wave was applied to the lower boundary of the model. After applying the dynamic load, velocity and displacement changes of the tunnel floor were higher than the rest of the tunnel. According to modeling results, the twin tunnels are quite unstable under static and dynamic loads and need a support system.