ABSTRACT
East Japan Railway Company (JR East) suffered damage to tunnels by several earthquakes and conducted detailed investigations on the causes of damage. Detailed investigations regarding the earthquake in 2011 confirmed the main cause of the damage to be the geological properties around the tunnels and structural properties of the tunnels. Restoration work was conducted to damaged members taking into consideration the cause. Then, the authors developed a new technology for seismic retrofitting tunnel roadbeds to prevent heavy seismic damage. A chain of maintenance cars was also developed to address cost and work duration. Following restoration work and seismic retrofit, a large earthquake occurred in 2022, but did not cause major damage to tunnels. The accumulation and retention of restoration techniques, proper judgment and timely decisions by JR East’s engineers, new seismic retrofit technology, and seismic retrofit have all ensured safer train operation and less seismic damage to tunnels.
