Study on the Tsunami Disaster Prevention Measure by the Deep-Draft Type Floating Tsunami Protection Wharf for a Vessel Moored at a Wharf

Huge earthquakes with tsunamis are more likely to occur in Japan, including the Nankai Trough earthquake, the Japan Trench earthquake, and the Chishima Trench earthquake; therefore, effective tsunami protection measures are needed for moored vessels in Japanese ports. The floating tsunami protection wharf (FTPW) has been proposed as a tsunami protection measure for vessels moored at wharves. The FTPW is a floating pier with a tsunami disaster prevention function, which can prevent the breaking of mooring lines and the grounding at a wharf by floating together with moored vessels during a tsunami. Although previous studies have mainly demonstrated the tsunami disaster prevention performance of the FTPW with a shallow draft, this study proposes the use of a deep-draft type floating tsunami protection wharf (DFTPW) with an even deeper draft. The disaster prevention performance of the FTPW and the DFTPW moored to 3,000 DWT class vessels were compared using the three-dimensional moving particle simulation (MPS) method. The results showed that both the FTPW and the DFTPW can prevent tsunami damage to moored vessels for the leading waves. However, the DFTPW has superior disaster mitigation performance than the FTPW for the backwash, and a combined measure using DFTPW and strengthening of mooring forces is necessary.