Although little attention is usually given to the armor porosity and armor randomness 5 of randomly-placed concrete armor units in mound breakwaters, significant model effects may 6 occur if armor porosity and randomness are different for prototype and small-scale models. 7Armor randomness and porosity are easier to control in small-scale models because they are 8 generally constructed by hand in dry and perfect viewing conditions; equipment and 9 environmental constraints make control at prototype scale more difficult. Results from 3D 10 small-scale placement tests are analyzed when cube and Cubipod units are placed with a small-11 scale crawler crane and pressure clamps. Armor porosity was not workable below 37% for cubes 12 and 35% for Cubipods; placement grids were obtained for feasible armor porosities, considering 13 row settlements during construction as well. A methodology to measure armor randomness 14 using high-precision laser scanning, similar to terrestrial LIDAR, was tested with small-scale 15 cube and Cubipod armor. Three armor randomness indexes (ARIs) measured the randomness 16 of cube and Cubipod armor; the values for ARIs were higher for Cubipod armor than for cube 17 armor. 18
Armor porosity and armor unit randomness are much easier to control in small-scale models constructed by hand than in prototype. Differences between design and prototype armor porosities and design and armor unit randomness can generate significant model effects. This paper describes realistic 3D placement tests with cube and Cubipod CAUs, using a small-scale crawler crane and pressure clamps. This research aims to estimate workable armor porosities at prototype scale and to determine the prototype placement grids to obtain the armor porosities commonly tested in laboratories. A new methodology based on laser scanning was developed to measure armor unit randomness. This methodology can be applied to both small-scale models and prototypes. Armor Randomness Indexes (ARIs) are proposed to measure the randomness of cube and Cubipod armor units. The ARI values were higher for Cubipods than for cubes.
Armor porosity significantly affects construction costs and hydraulic stability of mound breakwaters; however, most hydraulic stability formulas do not include armor porosity or packing density as an explicative variable. 2D hydraulic stability tests of conventional randomly-placed double-layer cube armors with different armor porosities are analyzed. The stability number showed a significant 1.2-power relationship with the packing density, similar to what has been found in the literature for other armor units; thus, the higher the porosity, the lower the hydraulic stability. To avoid uncontrolled model effects, the packing density should be routinely measured and reported in small-scale tests and monitored at prototype scale.
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