DAMAGE CHARACTERISTICS OF SEA WALLS DUE TO SCORING

The large number of coastal and port structures has been damaged by severe marine climates. Sea bed scoring at the foot of coastal structures such as sea walls is one of the main causes of damages and more than 50% of damaged sea walls is caused by it. The damaged sea walls are selected from the annual books of damaged facilities edited by Port Bureau of Ministry of Transport. Though the wave conditions at the damage are generally described, they are estimated by SMB method for the case without wave descriptions. The stone piled type vertical sea walls are likely to be entirely damaged by scoring, but blocked type ones are only damaged partly. Once the sea bed had been scored, incident waves are increased due to deepened with depth. Consequently, wave forces or wave overtopping become more severe. The required block weight calculated by Hudson's formula also increases. Therefore the countermeasures against scoring should be established immediately.