The stability of berm breakwaters, state of art and sensitivity analysis
School of Engineering
Berm recession plays a significant role in the design and assessment of berm breakwaters. In this study, different recession formulas were first thoroughly reviewed. Most of these formulas were developed based on mass armour berm breakwater tests, and some of the existing models contain many variables, while others have only a few parameters. Therefore, to determine the most significant parameters in these formulae, a comprehensive sensitivity analysis was conducted. It was found that the sensitivity of the recession to a particular parameter can be a function of several influencing parameters, and under some circumstances, some formulae are very sensitive to input variables. A comparison was made between the predicted recession and the measured one of the Sirevåg breakwater to investigate the performance of different formulas, which shows that Sigurdarson and Van der Meer (2013) formula performs better than others in this case. Furthermore, the impact of each governing parameter on the predicted berm recession was investigated. Results showed that the stability number is the significant parameter influencing the recession. However, there is an inconsistency between the formulae regarding the influence of T0 on the recession. Finally, experimental data was used to evaluate the sensitivities (of recession) obtained from different formulas, noting that these experimental data were obtained from research carried on a mass armour berm breakwater. The study revealed that Moghim et al. (2011) formulae showed reasonable performance regarding the influence of wave period T0 on the sensitivity of the recession, while Tørum et al. (2003) formulae was underestimating the sensitivity to T0. Moreover, it was found that Lykke Andersen (2006) formula is better fitted to the experimental data regarding the influence of the berm heigh (hbr) on recession.