Coefficient of uniformity and coefficient of curvature

#Coefficient of uniformity
The coefficient of uniformity is numerical value which determine the degree of uniformity. It is defined as the ratio of diameter of particle corresponding 60 % of fine to the ratio of diameter of particle 

corresponding to 10% of fine.

        Cu= D60/ D10

Wher, Cu = coefficient of uniformity
            D60 = diameter of particles corresponding to 60% of fine
            D10 = diameter of particles corresponding to 10% of fine.
Note : the particle size D10 is also known as effective size.

# coefficient of curvature
Coefficient of curvature is defined as the mathematically,
      Cc = (D30)^2/D10xD60

Note : Cu >4 and Cc is between 1 and 3 for well granded gravel.
            Cu> 6 and Cc is between 1 and 3 for well granded sand.