2017 年 5 巻 1 号 p. 10-26
A number of infrastructures for Sanriku Railway were seriously damaged by the 2011 East Japan Earthquake. In this paper, the damage by seismic loads and tsunamis are analyzed. In addition to serious damage by seismic loading, embankments, RC viaducts and bridges were washed away by the great tsunami in many places. A number of bridges and embankments could be effectively made highly earthquake- and tsunami-resistant by taking advantage of soil-reinforcing technologies. The design and construction in this restoration work took advantage of technologies that had been developed based on state-of-the-art geotechnical engineering, concrete engineering, and bridge engineering while aiming at cost-effective and fast restoration.
At Arakawa Bridge, the PCI girder was washed away and a new PC hollow girder with a small height, pier and geosynthetic-reinforced soil (GRS) embankment was installed. In the Shimanokoshi area, as requested by local people, a collapsed RC viaduct was replaced to a seismic- and tsunami-resistant geosynthetic-reinforced embankment covering slopes with concrete facing connected to geogrid layers reinforcing the embankment to prevent erosion of the backfill and scouring at the slope toes. At three places, in place of the collapsed three simple girder bridges, three GRS integral bridges, which are highly earthquake- and tsunami-resistant due to structural integration of reinforced backfill, full high rigid (FHR) facings and a continuous girder, were constructed and opened to service for the first time. In the existing embankments eroded by tsunami, the roadbed was restored by “reinforced roadbed” and embankment slope was covered with cast-in-place concrete facing or RRS (Reinforced Railroad/Road sloped structures with geocells and reinforcing steel bars) method.
