Effect of Nominal Stone Diameter on Stability of Reshaping Berm Breakwaters

Berm breakwaters are structures that reshape under waves action and reach to a stable profile. In thistype of breakwaters the units of the armor layer are allowed to move in order to take a final formwithout changing the serviceability performance of the structure. The remaining berm width - afterrescission - is the main criterion for stability of these structures. If the rescission become more than theinitial berm width, the breakwater will be unstable and failure will occur.In this paper the effect of nominal diameter on stability of reshaping berm breakwaters is investigatedby experimental studies. In order to consider the effect of this parameter in comparison with otherparameters, 120 tests have been carried out in the wave flume of Tarbiat Modares UniversityHydraulic Laboratory. The waves in all tests are irregular waves conforming JONSWAP spectralenergy. The amount of is assumed for graining.Results indicate that water depth has a considerable effect on berm rescission comparing to nominaldiameter. However, the initial berm width has the same effect as nominal diameter. The results alsoshow that by raising the position of berm to water level, rescission effect is reduced. On the other handby decreasing nominal diameter and increasing the initial berm width the same percentage ofrescission could be expected.