Stability of Low-Crested Rubble-Mound Breakwater Heads

Abstract

Three-dimensional physical models of low-crested, detached rubble-mound breakwaters were built, with their individual sections representing the following components of the breakwater: front slope, crest, back slope, total section (combination of the three previous sections), front head, and back head. The stability of the armor units in each of these sections was assessed, for different freeboards, using irregular waves. In a 1992 paper, Vidal et al. presented the stability criteria for the different trunk sections of this model breakwater. This paper focusses on test results from the head sections. A comparison between the stabilities of the head and trunk sections is also discussed. The stability of the back head (BH) section is found to be highly freeboard-dependent. For fully submerged conditions, the back head is one of the most stable sections of the breakwater. On the other hand, when the breakwater is nonovertopping, it is the least stable section. The front head (FH) section's behavior is similar to that of the front slope section of the breakwater trunk; its stability increases linearly as the freeboard decreases (i.e., as the breakwater becomes immersed).