EFFECT OF BROKEN DOLOSSE ON BREAKWATER' STABILITY

Abstract

Although the use of rubble-mound structures for protection of coastal areas is common throughout the world and considerable hydraulic design data have been developed to aid the designer, very little data are provided on the structural integrity of individual armor units and the effect of broken units on the stability of such structures. The forces to which such structures are subjected are complicated and vary with type and geometry of the structure, depth of water, bottom configuration seaward of the structure, water level relative to the crown of the structure, and wave dimensions. Since all of these parameters are involved, accurate determination of wave forces cannot be calculated; and although it is not impossible to model the structural strength of armor units or measure forces on individual armor units, there are physical limitations which make the tasks extremely difficult. There is one way, however, that a breakwater stability model, as it exists today, can provide useful information on this subject and that is to purposely break given numbers of armor units and observe the effect on the overall stability of the structure. Such tests have been conducted at the U. S. Army Engineer Waterways Experiment Station for the Atlantic Generating Station (AGS) Breakwater in which specific answers were desired; thus, the data are limited to the dolos armor unit. The data do provide, however, significant indications regarding the type and extent of breakage (cluster or random) that is most detrimental to the overall stability of the structure; whether costly reinforcing steel is warranted to assure reduced armor breakage; and where necessary, data from this type study can be used as a basis for setting maintenance criteria that will prevent deterioration of the breakwater due to armor unit breakage.