FAILURE MODE AGAINST IMPACT AND SOLITARY WAVES OF ARMOURED CAISSON BREAKWATERS PROTECTED BY A PARTIALLY FAILED ARMOUR LAYER

The response of composite caisson breakwaters against a partial failure of the armour layer is not well understood at present. Observations in the field have indicated that higher levels of damage can be observed in the caisson, and to try to understand the mechanisms at work laboratory experiments were carried out on a range of regular waves (including breaking waves) and solitary waves (to simulate tsunami type waves). The results show how for partially failed armour layers when a high energy wave acts directly onto the caisson much higher pressures can be expected than for when a full armour layer is present. Analysis of video recordings show how the wave changes shape by "piling-up" on top of the failed armour, and as a result their destructive potential is substantially increased.