Experimental evaluation of a rubble mound with one layer cubic blocks using video image analysis

Francisco Taveira-Pinto, Liliana Almeida, Lucília Luís

Tuesday 30 june 2015

16:15 - 16:30h at Africa (level 0)

Themes: (T) Water engineering, (ST) Experimental facilities and instrumentation

Parallel session: 7F. Engineering - Instrumentation

The armour layer of traditional rubble mound breakwaters is in general designed and built with two layers of blocks. However, in recent projects, one single layer of special blocks was designed and used (e.g. Accropode). The main reason for this change is the cost reduction due to the decrease in the number of blocks needed. The main objective of this work is the evaluation of the stability of models of cubic blocks rubble mounds in a single armour layer structure. It is also intended to improve the knowledge on physical modeling of single armour layer structures, leading to future developments. The physical tests performed in the Hydraulics Laboratory of the Faculty of Engineering of the University of Porto were also planned to analyze the velocity fields near the breakwater through image processing techniques. With this experimental setup, it was possible to study, not only the general behavior of the armour layer, but also the influence of the blocks’ density, the characteristics of the filter layer underneath the cubic blocks, the wave steepness and the depth at the breakwater’s toe. This study explains the origin and evolution of damage on the exposed layer of the structure. The interpretation of the effects on the physical model was supported by the outcome from the processed images, namely through the velocity fields, the dynamic areas and the envelope of the flow near the breakwater, Figure 1. At the same time, information regarding reflection of the wave on the structure was also obtained. The performance of the cubic blocks in a single armour layer structure was satisfactory, proving that this can be an alternative to the traditional solutions, with economic benefits.