Breakwater stability with damaged single layer armour units

The main objective of this research is to determine the effect of single layer armour unit breakage on the hydraulic armour layer stability and potential damage progression. A 2-dimensional model of a rubble mound breakwater with typical cross section was tested with individual and clustered positioned broken Xbloc armour units around the still water line. The residual stability of the armour layer was determined. The armour unit displacement and damage progression was assessed. It is concluded that breakage of single layer armour units has a significant negative effect on start of damage of the armour layer. Breakage of single layer armour units has no significant effect on failure of the armour layer. This damage behaviour leads to a long and gradual damage progression. This type of damage progression looks more like the damage progression of an armour layer consisting of rip-rap rock. The majority of the broken parts show little to no movement. It is therefore unlikely that rapid damage progression occurs due to broken parts damaging other units.