Desicjn Problem Preliminary Dasi gn 



Page no : 

 Calculated by 

 Checked by: 



Date 



65 Of/33 

 J. R- W 

 R.FT.J- 



f4 Mar. 73 



Reweimenf Ds^ign - Ocean 6icle of Island 



The ocean side of the island niII be 

 protected by a revetment using concrete 

 armor units * 



Ti^ pe of Nave Action 



The, depth at the site required to initiate 

 breaking of the ft ft design t^ov/r is : 



For Q slope in front of the structure 

 m ^ o 



H^= OJbdi, 



or 



0.76 



-^ = 25./ ft. 

 0.7t 



Since the depth at the structure (d< - 4o ft) 

 is greater than the computed breaking 

 depth (dk'' 23.1), the structure will be 

 subject ea to nan- breaking waves. 



Selection detiNeen Alternative Designs 



The choice of one cross section and for 

 armor unit type over another is prima rily an 

 economic decision reauiring evaluation of the 

 costs of various alternatives. A comparison 

 of several alternatives follows. 



Type of Armor Unit : Tribars vs. Tetrapods 



Structure Slope : l:t.Sj i:2, f:2.5 and f:3 



Concrete Density: l50lb/ft\t^lb/ft^i,nolbJft^ 



Sect 7.121 



* The use of concrete armor units will depend on 

 the QVailabil'ity of suitable quorrystone and on the 

 economics of using concrete as opposed to stone. 



8-65 



