2020 年 15 巻 6 号 p. 765-781
There exists many road embankments in Japan which are not earthquake resistant. For example, a road embankment collapsed at Okuradani IC in Hyogo Prefecture during the Great Hanshin-Awaji Earthquake of 1995. In 2009, a road embankment along the Tomei Expressway collapsed during an earthquake with epicenter in Suruga Bay. Road failure makes relief activity and transportation of goods difficult, causing social damage. Furthermore, recovery of damaged embankments takes much time and cost. Accordingly, it is important to conduct research on methods of construction which would help build embankments inexpensively and swiftly. Against this background, a full-scale experiment was conducted at E-Defense to confirm the validity of a method of construction that uses flexible container bag to pack soil for quick embankment recovery. Generally, flexible container bags are easy to handle, and ensure and maintain the earthquake resistance performance of embankments after the completion of recovery work, taking the longer life time of the reinforced structure into consideration. In the experiment, two kinds of reinforced structures with flexible container bags stacked differently were placed at either toe of the slope of an embankment of height 4 m, and shake tests were performed three times to compare the effectiveness of both reinforced structures. For both kinds of structures, the flexible container bags were stacked in two tiers and compressed from top and bottom using compression plates to make the structures rigid. One of the structures was one-tier type where the flexible container bags were stacked in series and the other was two-tier type where the flexible container bags were stacked along the side of the embankment. In the case with the target acceleration of sine wave of 376 Gal, crack occurred on the reinforced structure of one-tier type, but the embankment collapsed a little near the top of the slope. There was little displacement in both reinforced structures, hence, it is judged that the deformation would not impair the functionality of the road. As for the seismic performance, it can be said that the two-tier type would be slightly superior to one-tier type, however, this assumption cannot be evaluated decisively under the present circumstances. For practical use in future, form, size, workability, and economy of embankment should be examined for designing and construction which takes the specification of the structure into consideration.