Abstract
Yashio Dam is an asphalt concrete facing rockfill dam. Relatively large acceleration was observed at Yashio Dam in the 2011 Touhoku earthquake. Cracks occurred near the left and right abutments respectively. We had studied about the factor of generation of the cracks, and assumed that cracks occurred at the concrete joints in the dam crest because of the concentration of the strain during the earthquake. But, the length of cracks are about 70 to 80 m long in spite of the concentration of strain occurred at the limited area. Therefore, we put forward three hypotheses for the cause of development of the cracks. The one of them was the influence of the accumulated damage during the earthquake. We studied the past results of the cyclic bending tests to estimate it. Another was the influence of the strain occurred during the impoundment. We conducted the bending tests with the pre-bended beam to estimate it. The last one was the decline of the flexibility of the asphalt concrete by cracking. We conducted the bending test of the asphalt concrete beam with cutout and studied about the thermal stress. We finally found that the factor of the development of the cracks was the decline of the flexibility of the facing by the cracking during the earthquake and subsequent thermal stress.
