Experimental studies on the effects of placement method and packing density of cubic armour units on the stability of low-crested breakwaters

Abstract

Although concrete armour units have traditionally been used in two layers, the application of single-layer armour has attracted more attention in recent years because of its lower concrete volume and faster construction pace. Single-layer amour relies mainly on the contact between units to provide stability; however, installation of special armour types with surface projections for better interlocking, increases the possibility of breakage. During the last decade the idea of using bulky armour units such as cubes has been raised, and the application of these single-layer armour units has become common for high-crested breakwaters. However, the application of cube armours for low-crested breakwaters has not yet been fully investigated. This paper describes a set of experiments conducted to study the effects of the placement method and packing density of cubic armour units on the stability of low-crested breakwaters. The results show that the orderly placement of cubic armours on the slopes of low-crested breakwaters provides better hydraulic stability than an irregular placement. Regarding the packing density, the experiments reveal that it is possible to apply different placement densities on the breakwater slope below and above a certain level with respect to the toe of the breakwater.