Damage evolution in single-layer cube armoured breakwaters with a regular placement pattern

Abstract Single-layer cube (SLC) armoured breakwaters with a regular placement pattern are a relatively recent concept despite the cube being one of the oldest concrete units available. Limited investigation on the performance and hydraulic stability of this armour type is available to date. This work presents a quantitative assessment of the damage evolution for SLC armoured breakwaters with a regular placement pattern based on 2D physical modelling tests carried out at the University of Porto, Portugal. Tests were carried out for different armour porosities, wave steepnesses, and armour crest levels. A new method for automatically determining cube positions for each test was developed with image-processing techniques using advanced machine-learning tools. This method greatly reduces processing time since several images can be processed in batch mode. Innovative parameters to describe armour layer behaviour were derived and proposed for assessment and quantification of the damage evolution: exceedance probability of cube movements, mean grid orthogonality, and relative damage number for SLC. New damage level classification and criteria for initiation of damage are proposed for each of the parameters assessed. This analysis is focused on the initial stages of the damage, which are critical in designing new structures.