"4.= 



- ('''84 " '''16/ 



(5-1) 



M = the phi mean diameter of grain-size distribution (see Ch, 4, 

 ''' Sec. II) where 



M^ = 



(^84 + '''16/ 



(5-2) 



^84 

 ^16 



subscript b refers to borrow material 

 subscript n refers to natural sand on beach 

 84th percentile in phi units 

 16th percentile in phi units 





Figure 5-3. Isolines of the adjusted overfill factor, R^ ,for values of phi 

 mean difference and phi sorting ratio (from James, 1975). 



5-11 



