^ Crest Elev. Vories 



Mox. SWL = + 16 



MLWv 

 \ 

 Mm. SWL = -3 



Bottom Elev. ^ -40-'^*^ 



Bottom Elev. ^ -40- 



Figure 1. Preliminary rubble-mound cross section, hypothetical 

 Island (modified from Fig. 7-99 in the SPM) . 



The dolosse armor unit weights required were computed for structure slopes of 

 1 on 1.5, 1 on 2, 1 on 2.5, and 1 on 3, (cot8 = 1.5, 2.0, 2.5, and 3.0, respec- 

 tively) and for concrete densities of 150, 160, and 170 pounds per cubic foot 

 (24.3, 25.9, and 27.5 kilonewtons per cubic meter). Hudson's equation is given 

 by 



w„H^ 

 W = 



Kj)(Sj. - 1)3 cote 



where 



W = weight of armor unit required for stability 



w = unit weight of material of which armor unit is constructed 



H = design significant wave height 



S^ = ratio of unit weight of armor unit material to unit weight 

 of water 



= angle structure face makes with a horizontal 



Kj) = a stability coefficient. 



Hudson's equation was assumed to describe the relationship between required 

 armor unit weight, design wave height, structure slope, and armor material unit 

 weight. A zero-damage criterion was used. Some investigators (e.g., Bruun and 

 Johannesson, 1974)^ have suggested that Hudson's equation may not be valid for 



'^BRUUN, P., and JOHANNESSON, P., "A Critical Review of the Hydraulics of 

 Rubble-Mound Structures," Report R3-1974, University of Trondheim, Division of 

 Port and Ocean Engineering, The Norwegian Institute of Technology, Trondheim, 

 Norway, 1974. 



