Dynamic Tunnel–Soil Interaction in Soft Soils Considering Site-Specific Seismic Ground Response

Abstract

Tunnels constructed in soft soils are vulnerable to earthquake-induced ground shaking in seismically active regions. Since typically the tunneling depth is shallow and lies within the soft ground zone, there is a need for a complete understanding of tunnel behavior in soft soil. A wide range of case histories and various approaches adopted in seismic analysis of tunnels have been reviewed here. Seismic effects on tunnels and factors influencing damages to tunnels due to earthquakes are summarized in this article. In addition, the effects of various parameters on seismic behavior of shallow tunnel in soft soil were investigated in the present study. A fully non-linear plane strain analysis was performed using finite element (FE) program to examine the effects of input ground motion, shape of tunnel and tunnel-soil interface conditions on the seismic behavior of tunnel. Prior to parametric study, an approach for calibration of stiffness and Rayleigh damping parameters are discussed. It was observed that realistic field scenario can be simulated in numerical modelling with calibrated stiffness and damping ratio after conducting site-specific ground response analysis. Available analytical results are compared with developed numerical results. Circular tunnels found to perform better than other shapes during earthquake condition. Full-slip interface produces higher bending moment in tunnel compared to no-slip tunnel-soil interface condition. Maximum dynamic earth pressure occurs at shoulder of tunnel. The major findings here focus on the complex deformation modes and lining forces of tunnel during earthquake shaking, which can be used for design of tunnels in soft soil.