Abstract
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.
Highlights
A river embankment is a large-scale earth structure that mainly functions as a measure for flood prevention
Though the geological stratigraphy of the river embankment varies from location to location, a particular common feature is that the ground water table within the embankment is very shallow, keeping the earth embankment close to full saturation
In Japan, the seismic performance of the river embankment has been inspected in the last decades [1] since the significant subsidence of the Yodo River levee in Osaka was reported by the 1995 Kobe earthquake
Summary
A river embankment is a large-scale earth structure that mainly functions as a measure for flood prevention. Failure mechanisms due to liquefaction of embankment fill including but not limited to the pore water pressure distribution and the effective stress distribution can be clarified. Reconsolidation analysis was carried out as a continuation of the dynamic one to understand the mechanical as well as the hydraulic characteristics of the damaged embankment before restoration. The infinitesimal strain theory is capable of capturing some important characteristics of soil liquefaction at the element level, such as the increase in pore water pressure and the loss of effective stress, but can hardly replicate the embankment deformation pattern, especially under the extreme ground motion. To analyze the soil behavior within the embankment, the descriptions of partially saturated soil, such as the soil-water characteristics and the constitutive model for unsaturated soil, need to be introduced. Yoshikawa et al [11] conducted a numerical analysis on the seismic behavior of an unsaturated embankment
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