INTERACTIONS IN THE STABILITY OF TOE-BERM AND MAIN-ARMOUR FOR RUBBLE-MOUND BREAKWATERS : AN EXPERIMENTAL STUDY

Philippe Donnars, Michel Benoit

Abstract


This experimental study is concerned with one particular aspect of possible failure modes for a rubble-mound breakwater : the interactions between the toe-berm and the main-armour of the breakwater. Through a series of laboratory tests in a wave basin under long-crested and short-crested waves, we investigate the mutual influence of both these component parts of the breakwater on its general stability. The effects of several wave parameters are examined for four sizes of toe-berm stones. For the trunk section, experimental results are found to compare quite satisfactorily with existing design formulas both for the main-armour and the toeberm. As a general trend from the tests results, the interaction processes appear to have only moderate effect. Their major feature is an increase of damage to the armour when the toe-berm is unstable. On the opposite, minor effects of mainarmour on toe-berm stability were observed. In particular, the "toe-berm armouring process" (by units falling from the armour) appears to occur only marginally and under precise conditions.

Keywords


breakwater; rubble mound breakwater; toe berm; breakwater stabiltiy

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