Progression and Variability of Damage on Rubble Mound Breakwaters

Abstract

As a first step to develop a probabilistic method for the maintenance and repair of breakwaters, one 28.5-h test and two shorter tests, which were repeated twice, were conducted in a wave flume. Damage progression and variability were measured on a conventional rubble mound exposed to depth-limited breaking waves in sequences of storms with varying wave conditions and water levels. Measurements were made of 16 or 32 damage profiles every 30 min of irregular wave action. Each measured profile was characterized by the eroded area, depth and length of the armor layer, and the remaining cover depth. The mean and standard deviation of these statistical variables changed with damage progression, whereas the probability distributions of the normalized variables were practically invariant. The mean and standard deviation of the damage variables are shown to be represented empirically by the mean eroded area alone. The damage variability along the breakwater was significant. Finally, an empirical formula is proposed to predict the mean eroded area in sequences of storms for these three tests.