1. Department of Civil Engineering, Yokohama National University , 79–5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan
2. Pent-Ocean Institute of Technology, Penta-Ocean Construction Co. Ltd. , 1534–1 Yonku-cho, Nasushiobara-shi, Tochigi 329-2746, Japan
3. Environment Business Division, Penta-Ocean Construction Co. Ltd. , 2-2-8 Kouraku, Bunkyo-ku, Tokyo 112-8576, Japan
4. Marine Technology Institute Co. Ltd. , 2269–53 Seto-cho, Imari-shi, Saga 848-0043, Japan