Abstract:
Melby presents a formula to predict damage evolution in rubble-mound breakwaters
whose armour layer is made of rock, based on the erosion measured in scale-model tests and the
characteristics of the incident sea waves in such tests. However, this formula is only valid for armour
layers made of rock and for the range of tested sea states. The present work aims to show how
the Melby methodology can be used to establish a similar formula for the armour layer damage
evolution in a rubble-mound breakwater where tetrapods are employed. For that, a long-duration
test series is conducted with a 1:50 scale model of the quay section of the Ericeira Harbour breakwater.
The eroded volume of the armour layer was measured using a Kinect position sensor. The damage
parameter values measured in the experiments are lower than those predicted by the formulation
for rock armour layers. New ap and b coefficients for the Melby formula for the tested armour layer
were established based on the minimum root mean square error between the measured and the
predicted damage. This work shows also that it is possible to assess the damage evolution in scale model tests with rubble-mound breakwaters by computing the eroded volume and subsequently, the
dimensionless damage parameter based on the equivalent removed armour units.
