On berm breakwaters: Recession, crown wall wave forces, reliability

The paper reviews different formulae, Lykke Andersen (2006), Lykke Andersen and Burcharth (2010), Tørum (2007) and Moghim et al. (2011), for recession of berm breakwaters and compares calculated recession with previous and new recession test data. There are differences of the results by different formulae, but by and large all the formulae give reasonable results on the recession for shallow water berm breakwaters. It seems that the Lykke Andersen (2006) formula works best for the deep water cases although the Tørum (2007) formula seems to work as good for the homogenous berm breakwater case. The Moghim et al. (2011) formula was not included in the comparison for the deep water cases because the deep water cases are outside the validity of the formula. Results of tests on different alternative berm breakwater designs, which may be considered as practical/economic designs, have also been included, but without any comparison with any formulae simply because the formulae do not cover the specific designs. Wave forces from model tests on crown walls on berm breakwaters are presented and compared with an existing formula for wave forces on a crown wall on conventional rubble mound breakwaters, Pedersen (1995). It appears that the wave forces on a crown wall on a berm breakwater are smaller than the wave forces on a crown wall on a conventional rubble mound breakwater. Finally a probability of failure analysis of a site specific berm breakwater, the Sirevåg berm breakwater, Norway, is presented, using Monte Carlo simulations. The probability of failure analysis shows that the Sirevåg berm breakwater is extremely strong.