Abstract
The Yashio dam is the upper dam of Shiobara pumped storage power plant. It is a 90.5m high asphalt concrete facing rockfill dam. Two cracks occurred at the facing along the abutments of left and right bank and the volume of leakage increased in the 2011 Touhoku Earthquake. The maximum acceleration values were about 50cm/sec2 at the bed rock and 250 cm/sec2 at the crest respectively. They were less than the acceleration we considered at the design stage by the 2-D numerical dynamic analysis and 3-D model vibration test. We analyzed the recorded acceleration time histories and conducted a 3-D numerical dynamic analysis to pursue the mechanism of occurring of the cracks. After the studies, we found that the cracks occurred by the concentration of strain at the concrete joints on the crest of the dam, and summarized important considerations on the structure of the same type dam
