Abstract
Destruction mechanisms of coastal structures due to the 2011 Tohoku Tsunami were investigated on the basis of intensive field surveys in the southern part of Fukushima Prefecture. Numerical tsunami simulation was utilized to estimate the tsunami force exerted to the structure. The large difference in water pressure due to overflowing tsunami is found to be the essential mechanism of overturning destruction of coastal structures. The destruction was enhanced by the generation of large impulsive force due to a turbulent bore and the local scour of the foundation. The seaside slope of the seawalls was found to be essential as more significant damage was observed for upright seawalls than gentle slope ones. Inland topography also exerted dominant influences on the destruction of seawalls due to receding tsunami. The joint between the parapet and the seawall basement was considered to be a weak point unless it was appropriately reinforced by steel bars.
Highlights
Many coastal structures were destroyed by the massive Tohoku Tsunami generated on March 11, 2011
This study aims to describe the damage and analyze destruction mechanism of coastal structures on the basis of intensive field surveys combined with numerical tsunami computations
Intensive field surveys were conducted in the southern part of Fukushima Prefecture where various destruction mechanisms of coastal structures were observed
Summary
Many coastal structures were destroyed by the massive Tohoku Tsunami generated on March 11, 2011. Sato et al (2013) described their survey on coastal tsunami watermark heights in the 20 km radius evacuation zone. Many studies were reported on catastrophic damages in the Sanriku area located in Iwate and Miyagi Prefectures, studies in Fukushima Prefecture were limited owing to the evacuation from high radiation caused by the Fukushima Dai-ichi Nuclear Power Plant accident. Their survey was the first scientific survey after the nuclear power plant accident. (T.P. stands for Tokyo Peil which is the standard datum for topography in Japan) found on a coastal cliff in Tomioka, 7 km south of the Fukushima Dai-ichi Power Plant. Several follow-up surveys were conducted in Minami-Soma, north of the Fukushima Dai-ichi Power Plant (Sato et al, 2014) and in Nakoso and Naraha, south of the power plant (Sato et al, 2012; Sanuki et al, 2013)
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