Restoration of a tunnel damaged by earthquake

Abstract The Noto Offshore Earthquake ( ML=6.8 ), which occurred on February 7, 1993, damaged the crown arch of the tunnel over a length of approx. 10 m, resulting in the formation of a hollow when the ground soil collapsed about 10 m above the arch. In addition, cracks on the secondary lining and tunnel entrance and small collapses on the entrance slope face were observed. The tunnel rehabilitation work began with the survey results on the conditions of damages and natural ground. After adopting techniques involving air mortar filling, injection and consolidation into the hollow and collapse area, a section of the tunnel was widened by 1 to 2 m in order to remove the poor soil area. This paper discusses the damage to tunnel and the rehabilitation work that was required.