Title: Geotechnical Analysis of Mizuki Embankment Remains
Abstract: This paper presents the investigations of the historical remains of the Mizuki embankment, which was built in 664 AD with wide moats and a steep slope facing on one side. Considering the historical and local topographical features, it is thought that the Mizuki embankment was mainly used as a defence facility. The in-situ investigation reveals that the embankment was built using a Hanchiku (layer-compaction) method. Based on the slope stability analysis, it was found that brushwood reinforcement with a loading berm construction method proved the stability. Compacted inclined layers of soil and sand have been found in the embankment, and these layers might have been constructed to drain infiltrated water from the top of the embankment, thereby preventing the potential failure induced by heavy rainfall. The installation of the timber waterspouts across the embankment used a cut and fill method. Field investigation shows that below the wooden pillar at the west gate of Mizuki embankment, there was a compacted stiff clay layer. The seismic performance of the wooden pillar-clay system is shown to be effective by numerical analysis using program FLUSH.