Abstract
The 2004 Niigataken-Chuetsu Earthquake caused not only heavy casualties but also serious damage to infrastructures such as electric-power, water-supply, and transportation facilities. Power generation facilities, including three fill-dam reservoirs of the Shinanogawa Hydroelectric Power Plant were also heavily damaged; this plant is owned by the East Japan Railway Company. Differences in level caused by fissures along the fill-dam were brought about at the Asagawara Reservoir, one of the three reservoirs. Investigations of the site were carried out by trench-cut and boring methods, and showed that cracks and fissures were mainly superficial, and posed no major problem to the overall structure. The core also showed no damage. There was no damage to the function of the dam, therefore restoration was enabled despite the severity of the earthquake itself. Moreover, the cause of such damage was considered based on the investigation result.
