ABSTRACT
Rock tunnels suffered severe damage from recent large earthquakes in Japan, despite the empirical knowledge that tunnels tolerate earthquakes better than surface structures. Seismic design for rock tunnels have therefore become a fascinating subject for many tunnel engineers. However, even loading magnitude during earthquake is not fully understood. In a recent study, authors have installed dynamic measurement instruments in some actual rock tunnels and then obtained dynamic data which was measured during some large earthquakes. In this paper, outline of the results from the measurement is described and loading magnitude during earthquake for the tunnel is discussed through numerical analysis. The main discussion is based on the strongest aftershock of “The 2011 off the Pacific coast of Tohoku Earthquake”, occurred on April 7th, 2011. Major conclusions include: Strain of the tunnel lining is much smaller than compressive failure strain in a normal ground condition for rock tunnels according to the measurement results. Loading magnitude is approximately 26 kPa with k-ratio of 0.5 to simulate the strain of the lining in a simple static numerical analysis.
