The ratio of D60 and D10 sieve sizes in the sieve analysis of granula...
Coefficient of Uniformity / Uniformity Coefficient
It is defined as the ratio of D60 and D10 sieve sizes in the sieve analysis of granular material.
Higher is the value of Cu,the larger is the range of the particle size.
Cu = D60/D10
For uniformly graded soil, Cu = 1
For well graded sand, Cu > 6
For well graded gravel Cu > 4
Coefficient of Curvature / Curvature Coefficient:
C
c =
For well graded soil, 1 < cc="" />< />
For gap graded soil, 1 < />c or Cc > 3
where
D60 = size at 60% finer by weight
D30 = size at 30% finer by weight
D10 = size at 10% finer by weight = Effective size