where 



r = thickness of cover layer (m) 



n = number of armor units comprising the layer 



W = weight of individual armor unit (metric tons) 



w = unit weight of stone material (concrete or quarrystone) 



k. = layer coefficient of rubble structure 



A 



(d) Number of Stones Required. 



where 



N^ = A n k^ (l - ^ j U^ 



.2/3 



(eq. 7-122) 



A. 



Nj, = number of armor units or stones in cover layer 



A = area (m ) 

 P = porosity (%) 



k, and 

 A 



P from Table 7-13. 



8-59 



