Numerical Analysis of Damaged River Embankment during the 2011 Tohoku Earthquake Using a Multiphase-Coupled FEM Analysis Method

According to the investigation and restoration report by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT, 2011), 1195 river embankments were damaged in Tohoku region during the 2011 Tohoku earthquake. The failures of the river embankments were typically due to the soil liquefaction of embankment fill. In the present study, a severely damaged river embankment along Naruse River was simulated by using a three-phase coupled finite element program, namely, COMVI2D-DY, which is developed to analyze large deformation behavior of partially saturated soils. In addition, the reconsolidation process after the earthquake was simulated. To reproduce the reconsolidation behavior, a cyclic elastoplastic constitutive model based on nonlinear kinematical hardening rule was modified by considering stiffness recovery during reconsolidation. From the analysis results, it could be concluded that the numerical method is able to reproduce the key characteristics of the actual damaged pattern; the embankment is heavily damaged and deformed largely towards the land side, and the settlement at the top of the embankment is 2.5 m. In addition, realistic simulation results can be obtained from the reconsolidation analysis.