Therefore, for instance, H^j ^ ._,q = (2.5) (1.08) = 2.7 m (88.8 ft) 

 (b) From Table 7-9, for Z) = 5 to 10 percent 



^D=0 



— = 1.08 



H, 



^D=0 1.08 

 Since the H causing 5 to 10 percent damage is 2.5 m , 



"^0 = 1758 = 2-^ "^ ^^-^ ^^^ 



(c) To determine the damage level, a ratio of wave heights must be 

 calculated. The higher wave height "H" will be the ^d^q for the zero- 

 damage weight Wn ^ . The lower wave height "Hnn" will be the Hn q for 

 the available stone weight Mjiy . 



Rearranging equation (7-116), 



\l/3 



H = (S^ -1) 



W K^j cot e 



from which 



w ^1/3 



D = 



%=0 \^AV 



Since ^AV ~ 0«75 ^D=0 



"^D^O 



1/3 



%=0 \0-75 ^D=0 



"H" _ r 1 a/3 _ , 

 H ~ '-n 75-' ~ 



10 



This corresponds to damage of about 5 to 10 percent if the available stone 

 is used. 



*************************************** 



e. Importance of Unit Weight of Armor Units . The basic equation used for 

 design of armor units for rubble structures indicates that the unit weight 

 w^ of quarrystone or concrete is important. Designers should carefully 

 evaluate the advantages of increasing unit weight of concrete armor units to 

 affect savings in the structure cost. Brandtzaeg (1966) cautioned that 

 variations in unit weight should be limited within a range of, say, 18.9 



7-213 



