Interaction of Urban Underground Twin Metro Tunnels Under Static and Earthquake Loading

Abstract

New Delhi is a city affected by near/far-field earthquakes, where underground metro construction activities have been undertaken since the early 2000s. Due to the seismic effects, these structures are designed by conventional force/displacement methods. The present study validates the efficacy of these methods, numerically. For this, varying geotechnical conditions in static and seismic cases were quantified with the expected ground motion. Bored tunnels at different cover depths were modeled in 2D and 3D, to ascertain the static response of these structures, followed by a true dynamic analysis. It was found that conventional design procedures using force methods gave conservative estimates for increments on the tunnel liner. Also, the importance of a full dynamic analysis could not be ignored because (i) higher surface spectral responses were found at the tunnel pillar location and (ii) the cumulative strains on the tunnel liner were found to exceed permissible limits.

Comparison of Different Combined Multiple Tunnel Complexes in Soft Soil under Seismic Vibrations

“…Alielahi et al [16] developed amplification coefficients for parallel twin tunnels based on varying embedment depth and interspacing using the boundary element method to modify standard design spectra. Jishnu & Ayothiraman [20] numerically studied the seismic behavior of different construction arrangements, i.e., vertical and horizontally aligned twin tunnels, to determine the effect of pillar width and identify the better performer between them. Azadi & Kalhor [21] also conducted a similar study to evaluate the effect of excavated tunnels on existing tunnels based on embedment, soil cohesion, cementation, etc.…”