Performance of reinforced soil walls during the 2011 Tohoku earthquake

ABSTRACT: The 2011 Tohoku earthquake off the Pacific coast of Japan (M_w = 9.0) contained a huge source region of approximately 450 km by 200 km and caused extensive damage to various structures. Damage caused by the tsunami was tremendous and many lives were lost. In addition to the damage to concrete structures, seawalls were seriously damaged, probably as a result of scouring. On the other hand, some reinforced soil walls were barely damaged, although they were inundated by the tsunami. This paper briefly reviews the reinforced soil walls in Japan and then summarises the seismic performances of approximately 1600 walls in the 2011 Tohoku earthquake. It also reports some case histories for the reinforced soil walls that were subjected to the direct impact of the earthquake (shaking) and the tsunami. Although seismic motion was much higher than the design value for a wide area and the impact of the tsunami was not considered in the design, fewer than 1% of the walls were seriously damaged and more than 90% showed no damage. However, some damage was found at the backfill and facing panels where the soil was not properly covered and protected against erosion by the tsunami.