Abstract
The abrasion process of a slit type seawall constructed on a rocky coast was investigated by field observation data. The movement characteristics of 100 kg round stones due to wave action were disclosed by hydraulic experiments with a model scale of 1/20. The abrasion damage mainly appeared near the still water level, which was corresponding to the position with the highest collision rate. It was also shown that the collision rate was higher for longer wave period conditions. The relationship between the wave height and the collision speed was shown for three wave period conditions based on the result of video analysis on the stone movement pattern due to wave action. The characteristics of flow patterns and overtopping waves were investigated up to the design wave condition by hydraulic experiments with a model scale of 1/40. The abrasion rate of the slit type seawall was estimated to be 10 mm / year by the existing experimental formula using observed wave data at the nearest NOWPHAS station. The estimated abrasion rate was nearly the same as the observed value. Furthermore, the repairing method was proposed for the damaged slit type seawall based on the results of the wave overtopping test.
