Abstract: The number of dams in Japan directly managed by Ministry of Land, Infrastructure, Transport and Tourism (hereinafter call MLIT) which have been in service for 50 years or longer will double from their present level in the next 10 years and increase 3.5 times in the next 20 years. To efficiently manage dams with limited maintenance budgets and personnel, maintenance costs and labor requirements must be reduced.
We performed a full inspection of a dam constructed 50 years ago, the Futase Dam on the Arakawa River of the Arakawa River Systems. Based on the results, we then performed case studies of efficient maintenance of the dam body.
As a result of the research, regarding efficient maintenance methods, a number of proposals were made from the perspectives of (1) ensuring reliability of measurement data, (2) monitoring deterioration, (3)preparing to large earthquakes, (4) and building and using databases.

Key words: Bathtub curve, maintenance, deterioration, large earthquake

摘要： 日本国土交通省（Ministry of Land, Infrastructure, Transport and Tourism, MLIT）直接管理的大坝中，服役年限超过50年或更长时间的大坝数量在未来10年会翻番，在未来20年会增加3.5倍。为在有限的维护预算和人员条件下对大坝进行高效的维护，必须降低维护成本和劳动力要求。
荒川河系统中坐落在荒川河上的Futase大坝建于50年前，专家们对该坝进行了一次全面的检查。基于检查结果，对坝体如何高效维护进行了案例研究。
研究结果，关于高效的维护方法，从以下方面提出了许多建议：（1）保证测量数据的可靠性；（2）老化病险监测；（3）大地震准备；（4）数据库的建立和使用。

关键词: 浴盆曲线, 维护, 病险, 大地震