Effects of Irregular Wave Trains on Rubble-Mound Breakwaters

Results of model tests on a typical cross section of a rubble-mound breakwater are presented. The structure was protected against wave attack by a cover layer consisting of a double layer of dolos armor units of 43 g. These units were intended to represent 0.19 ton prototype units to a scale of 1/16. All tests were carried out on a slope of 1:1.5. The armor units were first submitted to attack by nonbreaking waves of the regular type and then by nonbreaking waves of the irregular type. Two kinds of irregular waves simulating a narrow-band spectrum and a wide-band spectrum were used. Wave heights and periods were measured with the help of resistance type wave gages. Two types of damage were identified: the stable and the unstable damage. The test results are presented showing the significant wave height and the damage coefficient versus the stable and unstable damage.