Supporting mountain road loops with lightweight embankments - EDO-EPS construction method

The prefecture's first circular bridge was completed in Kamogawa City, Chiba Prefecture. The construction of this circular bridge, which is part of the Ichihara Amatsu Kominato Prefectural Road (36 km long), was a long-awaited project for the region.

This road is an important axis connecting the inland area of ​​the Boso Peninsula and the Pacific coast, but there are sections where it is difficult to pass each other and the curves are very sharp, and due to the steep terrain, the cliffs are prone to collapse due to heavy rain. This happens frequently.

Therefore, the prefecture began to renovate the particularly narrow sections in 1991, and the road was finally opened to traffic. The roadside has been transformed into a road that is easy to use, even for first-time visitors, as it is blessed with abundant nature, such as Mount Kiyosumi and Yoro Valley, and also functions as a tourist road.

This bridge, named the ``Kiyosumi Mountain Road Loop Bridge'', was used as a measure to eliminate the elevation difference of more than 20 meters with a wide road radius without any terrain restrictions (the elevation difference at the bridge section is also about 8m), which also has the secondary benefit of being less prone to landslides due to moving the road away from the slope.

For this project, Okasan Ribic supplied materials for the EDO-EPS construction method, which reduced the load on the widened road, taking into account that the embankment connecting the ground to the bridge is located in a steep mountainous area. Okasan Construction Company was in charge of the construction work as a subcontractor.