Research on Difference of Seismic Damage Cases of Eaigawa River Embankment by More than Once Earthquakes and Effect of Restoration Measures

Abstract

The river embankment of Eaigawa river system in Miyagi prefecture has been accumulated the damages by the huge earthquakes, such as the 1962 Northern Miyagi Earthquake, the 1978 off Miyagi Earthquake, and the 2011 off the Pacific coast of Tohoku Earthquake. In this report, the characteristics of vulnerable places and the effects on the earthquake by the countermeasure for leakage and scour were evaluated by comparing the damage cases of the Eaigawa river embankment which were collected and organized. The results of the analysis show that the seismic damage is prone to increase as the time is shorter after the completion of river improvement work because the intensity of expression for effect of aging cannot be expected. Moreover, it was found that the seismic damage is likely to reduce in the construction place of the cutoff sheet-pile and concrete block revetment of leakage and scour countermeasures. In conclusion, the effect on the damage reduction by the leakage and scour countermeasures are important in finding for the efficient implementation of the river improvement project due to its long linear structures, but the seismic countermeasure is quite difficult.