Tunnel s behavior under seismic conditions in soft Soils and Rocks

The tunnel industry has considered that tunnels, especially tunnels in rock, are naturally resistant to earthquake action, including faulting, shaking, deflection and ground failure. As the number of case histories of tunnels subject to earthquake action has increased the industry has started to recognize that, although tunnels in rock have good resistance against earthquakes generating peak ground accelerations (PGA) lower than 0.5 g, it is important to include the dynamic forces and displacements generated by seismic ground motions in the design process to obtain a more reliable design. These additional earthquake forces affect the final design, potentially requiring changes to the ground support and additional reinforcement of the concrete lining. The present study highlights the behavior of tunnels in soft soils and rocks under seismic conditions by using the finite element (FE) analysis. The developed numerical model is compared with available analytical solutions. Thereafter, a series of parametric studies are carried out by varying the tunnel embedment ratio, soil and rock tunnels interface conditions, lining thickness, shape of the tunnel, and input ground motion. It has been observed that distortion in the tunnel lining is dependent on the depth of embedment and the flexibility ratio of the tunnel.

کلیدواژه ها:

Seismic design ، Earthquake impact ، Tunnel lining ، Seismic response