Deformation Analyses of River Dike on Liquefiable Ground Affected by Different Earthquake Motions

Severe damages of river dikes caused by liquefaction have been often observed. In previous earthquakes, it has been reported that many river dikes were deformed by the liquefaction during earthquake. The river dike in the middle region of Shinano River is built on the loosely deposited sandy layers. Therefore, a large deformation of the river dike by the liquefaction is expected. It is very important to understand the deformation mechanism of the river dike by liquefaction in order to prevent a future damage of river dike along Shinano River. In this study, effective stress based finite element analyses were carried out by the program code "LIQCA" to reproduce the past damage and to compare the damage of the river dike by different earthquake motions. Three earthquake motions by the 1964 Niigata earthquake, the 2004 Niigataken Chuetsu earthquake and the 2007 Niigataken Chuetsu-Oki earthquake had different duration time and acceleration amplitude. The comparisons among damages by three earthquakes were carried out. As the results, it was confirmed that the duration time and the acceleration amplitude of earthquake motion were key factors which affect the damage of the river dike.