Improvement in seismic resistance using replacement/counterweight fill method for existing high embankments on inclined ground constructed with various embankment materials

The seismic resistance of existing embankments has become a significant issue as embankments fail frequently because of earthquakes. However, there are only a limited number of methods that can improve the seismicity of these existing embankments. In this study, a new improvement method, called the “replacement/counterweight fill method”, is proposed to improve seismic resistance. Two high embankments, of different materials, were constructed on an inclined ground and the replacement/counterweight fill method was applied to them. A seismic response analysis was performed to investigate the effectiveness of the improvement in seismicity. It was found that the replacement/counterweight fill method reduced the area of shear strain by more than 30%, suppressed the deformation of the embankments, and improved the seismic resistance. Along with the increase in the height of the counterweight fill, the effectiveness of this method increased and the seismic resistance was improved even further. Applying the replacement/counterweight fill method contributed to the improvement in seismic resistance by increasing the mean effective stress inside the embankments, decreasing the specific volume, decreasing the stress ratio (q/p’), and reducing the plastic deformation caused by the increase in the overconsolidation ratio due to unloading during the earthquake. Increasing the height of the counterweight fill was seen to be more effective for suppressing embankment deformation than increasing its width because increasing the height meant that the area of the reinforcement effect would be expanded.