Abstract
The Fukushima Daiichi Nuclear Power Station suffered great damage due to the Tohoku Regional Pacific Offshore Earthquake that occurred on March 11, 2011 and the accompanying tsunami. Due to the influence of the leakage of contaminated water including high concentrations of radioactive materials, Radioactive substances were detected from the seabed soil in the harbor. In order to prevent seabed soil containing radioactive material from diffusing out of the harbor, seabed soil was coated with cement mixed soil. In FY 2012, we covered 72,600 m2 in the first construction and covered 180,600 m2 in the second construction in FY 2014. In the 2nd construction work, cement mixed soil mainly composed of sand was selected, as it required earlier strength than the cement mixed soil used in the 1st construction. Material separation at underwater casting, which is a problem of cement mixed soil mainly composed of sand, was solved by developing special additives and casting jigs.
