Seismic response of metro underground tunnels

Metro underground construction is a mass rapid transit system in all metropolitan cities throughout the world. It is very important to study how underground tunnels suffer damage during earthquakes so that human life could be protected and the service efficiency attained. Selection of realistic ground motion of earthquake is very important for their seismic analysis. In this paper, case study of Delhi metro underground tunnels has been taken for analysis and their response to Chamoli 1999 earthquake of lower Himalaya has been studied. Realistic response of the tunnels can be obtained if the time history of earthquake for which analysis is carried out matches the expected earthquake at that particular site. Response spectra compatible time history was therefore first generated for Delhi zone. The tunnel-soil system has been simulated by finite element program: Plaxis 2D. Analysis suggests that actual earthquake for another site may overestimate or underestimate the response at the desired site and forces in RC liners and settlements in soil-tunnel system have been found to be higher in deep tunnels than in shallow tunnels.

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