港湾における長周期波対策の現状と課題

抄録

Long period waves with period of 30 to 300s causes the troubles in loading and un-loading of large cargo vessels and breaks of mooring ropes. Such damages are amplified by the resonance of mooring system composed of vessel and hawser to long period waves because the natural oscillation period of the system agrees with that of waves. The countermeasures represented by the extension of offshore breakwaters, improvement of mooring system and establishment to warning system have been proposed to prevent the long period wave turbulence.
In the paper, the practical countermeasures employing the extension of offshore breakwater and development of long period wave absorber are proposed. Numerical modeling is carried out to evaluate the effects of countermeasures to reduce long period wave heights in harbor. The simulated results demonstrate that offshore breakwaters extended appropriately may reduce the incident energy of long period waves and may increase the rate of effective handling days and that double slit caisson sea wall is applicable to reduce the energy of reflected long period waves.