Research on the Effect of Risk Mitigation Measures Against Earthquake for Mountain Tunnel Through Static Loading Test

摘要

Rock tunnels are generally considered to have the required structural strength to resist earthquakes; recently, however, a number of rock tunnels in Japan have suffered severe earthquake damage to their permanent lining. Although several countermeasures are available to mitigate the risk of such damage, their mechanism and effect are not fully understood. In this study, static loading experiments assuming a mountain tunnel affected by an earthquake were carried out to clarify the mechanism of lining damage and the effect of countermeasures. The results revealed that the presence of void spaces behind the lining reduces the structural load-bearing performance, especially in tunnels constructed by conventional timber lagging method. Moreover, reinforcement such as inverted arch, rock bolts, lining rebars and carbon-fiber sheets for inner surfaces can potentially mitigate the risk of lining collapse due to earthquake.