We conducted a basic study to establish a method for detecting dam abnormalities using an Autoencoder based on seismic data acquired at dams during earthquakes, with the aim of efficiently assessing dam damage when dams are affected over a wide area due to a large-scale earthquake. Specifically, we conducted abnormality detection using Autoencoder on seismic data from two dams of different types that had temporarily decreased their horizontal primary natural frequencies after large earthquakes in the past, and evaluated the accuracy and analyzed the causes of misjudgment. Furthermore, based on the results of these investigations, we have discussed the challenges and directions for practical application.

The Mizuho Dam is a center core-type rockfill dam. On September 6, 2018, an earthquake was occurred in the eastern Iburi region of Hokkaido recording a maximum seismic intensity of 7. Mizuho Dam, located about 19 km away from the epicenter, suffered extensive damages: cracks near the top of dam body and the collapse of slopes around the dam reservoir causing soil and sand to flow into the reservoir. As a result, restoration work on The Mizuho Dam was carried out as a national disaster restoration project and was completed in 2023. This paper reports on the damage to the dam caused by the earthquake, and outlines of the repair work.

Naruse Dam is a trapezoidal CSG dam certified as a river structure as part of the Omono River System River Improvement Project, and is the largest multipurpose dam in Japan, the first to exceed 100m in height. Naruse Dam is located in one of the snowiest areas in the Tohoku region, and because pouring cannot be carried out in winter, pouring of CSG and concrete is limited to a seven-month period from mid-April to mid-November. For this reason, the construction of the embankment, the largest of its kind in Japan, was undertaken as quickly as possible while ensuring quality and safety. In this article, we report on construction examples to date, since the pouring of CSG was completed in 2024.

Naruse Dam is a trapezoidal CSG type dam, and the concrete aggregate and CSG material, which are the materials of the dam body, are taken from the same mountain. In recent years, it has been required to improve the collection rate of raw stones for aggregate or CSG matrix in dam construction. Since CSG materials are produced only by crushing locally generated materials, the quality of CSG materials varies greatly, and it is necessary to monitor the material properties by laboratory tests during production. Therefore, a system for continuously monitoring particle size and surface water content of crushed materials produced using image analysis and RI moisture meter was applied to the crushed materials of quarry sites, and the effectiveness of the system was confirmed. In this paper, the outline and application result of the simple and rapid evaluation method adopted for the improvement of the extraction rate of the source rock base metal and the continuous monitoring system of particle size and moisture content of CSG material are shown.