In order to estimate the vibration characteristics of rockfill dams flexibly, a method using microtremor measurement was investigated. In the mountainous area where the dams are located, the amplitude level of microtremors is always very small, so there is a concern that the dam body may not be sufficiently excited. Therefore, we performed measurements using several types of sensors and confirmed the validity of the measurement data. In addition, the microtremor measurements and seismic observation records were compared with respect to the amplification characteristics of the embankment, and the relationship between the two was examined. Finally, microtremors were measured at multiple points in the horizontal direction at the crest to obtain the vibration mode of the fill dam.
In Japan, there is increasing demand of improvement of reservoir operation system. In the case of cascaded hydropower dams, using them for controlling flood is considered, but due to data lacking or conflict of interest, discussion hasn’t been developed. In this study, cascade model of hydropower dams and proposal of preliminary discharging method was made. As a result, 70 million yen of energy loss can be reduced in one flood on average, and flood controlling was effective if cooperate operation and preliminary operation are properly combined.
Dynamic analysis of a dam is generally conducted including its foundation in the seismic design of dams. In the analysis, the acceleration of the base of foundation is calculated in the foundation model without a dam, and this base acceleration is applied in the whole structural system of a dam and foundation. The paper discussed the interpretation and consideration on this pullback procedure. In addition, the remark of the analysis was discussed.
It is required to develop technology to maximize the flood control function by making more effective use of the existing dam reservoirs in order to deal with the severe heavy rain disasters that frequently occur in Japan and all over the world in recent years. Since 2018, the authors have been developing the integrated dam management system for super typhoons in the Cross-ministerial Strategic Innovation Promotion Program (SIP) by the Cabinet Office of Japan. In this report, the results of runoff simulations by applying statistical down-scaling method to the long-term ensemble rainfall forecast by the European Centre for Medium-Range Weather Forecasts (ECMWF) on a dam basin where a large inflow occurred during the 2019 Typhoon No. 19 “Hagibis” were shown. By the analysis, the amount of rainfall, reservoir capacity required for flood control and re-storage after the flood were estimated over time and stochastically. It was shown that it is possible to set appropriate pre-release rates according to changes in the forecast. These results will be applied to the development of the system that coordinates the operation of multiple dams in the river system and maximizes the total flood control capacity of them.
In order to evaluate the seismic performance of dam bodies and related structures, it is important to collect and organize past earthquake damage cases of dam structures and analyze the seismic performance of those structures. In this paper, I collected and organized the damage cases related to the dam body and related structures in Japan and abroad in the case of the large-scale earthquakes, and analyzed the damage conditions. Then, based on the actual conditions of the earthquake damage, I examined factors to be considered in dam seismic performance evaluation for future.
The new Katsurazawa Dam construction is a project to raise the Katsurazawa Dam which is the first multipurpose dam in Hokkaido, built about 60 years ago, as a part of the Ikushunbetsu River comprehensive development project, by 11.9 m with the same dam axis. By increasing the dam height by 1.2 times, the total capacity of the reservoir will be 1.6 times, which is an efficient dam redevelopment. Raising dam under operation was done in about two years in Hokkaido, where had to include five months of winter suspension. This paper reports on the results of concrete casting achievement, including the collection of rock and the production of aggregates, and the characteristics of the construction of raised dams.