w w = unit weight of water; 64.0 lb/ft 



6 = angle of the structure slope measured from the horizontal in 

 degrees; cot 6 = 1.5 



K D = stability coefficient for rough angular armor units; = 2.0 



For the design conditions at the site, W = 3,300 lb. The acceptable range 

 for W is 2,500 to 4,500 lb with 50 percent of the individual stones weighing 

 more than 3,300 lb. 



The bedding and core stone directly beneath the primary armor units is 

 3-in. to 8-in. stone. 



The crest width of the breakwaters is calculated from the following 

 equation (SPM, 1984): 



B = n k d (WAv r ) 1/3 (A3, Equation 7-120, SPM) 



where 



B = crest width, ft 



n = number of stones (n = 3 is recommended minimum) 



Jt d = layer coefficient; 1 .00 



w r = unit weight of stone; 165 lb/ft 3 



Using this equation, the crest width is calculated to be 9.5 ft. 



Since the breakwaters will be exposed to breaking waves, a quarrystone toe 

 berm is required to support the primary cover layers. The width of this berm 

 is 6 ft and the thickness of the berm is 3 ft. A typical section of the 

 breakwater is shown in Figure A3. 



Foundation analysis 



Vibracores were taken at four offshore locations beneath the area of the 

 proposed offshore breakwaters. A semi-portable coring system was used. 

 Cores ranging in length from 4 to 5 ft were obtained. Analysis of these cores 

 indicated that a surface sand layer overlies the entire area, ranging in 

 thickness from 10 to 20 in. and that no settlement is expected, either initially 

 or in the long term. 



Functional Breakwater Design 



Shore-parallel breakwaters constructed offshore provide protection by 

 reducing the amount of wave energy reaching the leeward water and shore 



Appendix A Case Design Example of Detached Breakwater 



A7 



