HO SY QUOC

A Study on Long-term Settlement of Expressway Embankment on Soft Ground

Ohtsuka Satoru

 The Expressway of Nihonkai Coast Tohoku is a highway with a total length of approximately 340 km from the Central JCT of Niigata to Aomori city along the Sea of Japan through Sakata City, Akita City, and other places. In Niigata Prefecture, it is about 90 km and constructs the embankment based on the road structure on the soft ground including of the seaside and the river. After the time of being used , it has affected the traffic jams by some unsolved problems until now. It needs to have been improved. The method of the overlay construction is being proceeded as a longitudinal correction because the level difference occurs at the connecting part between the abutment and the embankment when the subsidence continues over a long period of time. As a results, the safety of traveling on the road is impaired. However, since the overlay increases the embankment load year after year, it has caused a vicious cycle such as causing a settlement and prolonging the road surface repair. In addition, the fluctuation of the groundwater level in the embankment functions as a change in the overload. In this research, the objective is to clarify the long - term settlement mechanism of the embankment of the examination section (between Shibata IC - Nakajo IC of Tohoku Expressway on the Japan Sea coast) by a numerical analysis (elastoplastic consolidation deformation analysis).
 In this study, we investigated the factors of the embankment settlement by numerical analysis for changing the saturation and unsaturation of groundwater level in embankment. The groundwater level fluctuates about 3 m depending on the condition of the filler material. From the repeated consolidation test of the undisturbed viscous soil, it is shown that the subsidence of the land subsidence progresses repeated loading and long - term subsidence of the ground which can be evaluated appropriately by elastoplastic consolidation deformation analysis.