damage development. For the experiment discussed herein, the structure crest height 

 above the toe of 30.5 cm corresponded to an elevation of approximately one significant 

 wave height above the still water level for the larger wave conditions tested. This is 

 typical of prototype structure crest heights. This crest height was specified so that 

 results from this experiment could be used for analysis of prototype breakwaters with 

 higher crest heights because the damage measured with the shorter structure should be 

 relatively greater than that of a taller structure. The effect of wave overtopping on 

 stability will be discussed in more detail later in this chapter. 



4.2.2 Experimental test conditions 



The test conditions for the initial study are summarized in Table 4.1. Note 

 that wave period variation and armor gradation variation experiments are not listed in 

 this table, but were added, and are discussed in Chapter 7. The waves had relatively 

 long periods in this initial experiment, as this produces the lowest stability (Figure 3.3). 

 The depth-to-wavelength ratio h,/Lp at the structure toe was approximately 0.07 for this 

 initial experiment, where Lp was computed using linear wave theory and the spectral 

 peak period. This shallow-water breaking wave is also typical of design conditions on 

 United States coastlines. 



4.23 Armor layer and underlayer 



The mass distributions for armor and underlayers for the initial test series 

 are shown in Figure 4.4. The armor layer consisted of uniformly hand-sized stones with 



56 



