Seismic Analysis of Twin Tunnels in Liquefiable Soils

Underground structures are an integral part of the infrastructure of modern urban. If these structures be built in seismic regions, stability control will be necessary. In this research, dynamic analysis of Tabriz twin subway tunnels by using FLAC2D software has been examined. The main problem in dynamic analysis of this project is the tunnel located below the water table and soil liquefaction ability in the part of the tunnel route. Considering both dynamic loads and pore pressure, the suitable behavior model for soils will require. Mohr-Columb constitutive model used in static analysis and Finn constitutive model used to simulate excessive pore water generation during dynamic loading. For dynamics investigation, used two earthquakes levels; DBL and MCL, and three earthquakes records; Duzce, Loma prieta and Changureh- Avaj. Stability of tunnel Maintenance system under static and dynamic loads investigated. The analysis results indicate that, different earthquakes load conditions affect pore water pressure distribution and subsequently changes liner stresses. Increasing the loading dominate frequency caused the forces of the tunnel lining and pore pressure to decrease. Although, as the loading amplitude decreases, liner stresses and excessive pore water generation decreased.