# What is Uniformity Coefficient(Cu) And Coefficient of Curvature(Cc) of Soil

## Uniformity coefficient(Cu)

The uniformity coefficient is a measure of particle size range and given by the ratio of D60 and D10 size of particles. It is denoted by Cu.

Thus, Cu = D60/D10

Where,

• D60 = Size of the particle corresponding to 60% finer and,
• D10 = Size of the particle corresponding to 10% finer.

## Coefficient of curvature(Cc)

The coefficient of curvature is a measure of gradation of particles and given by the following expression:

Cc = (D30)2/D60.D10

Where,

• D60 = Size of the particle corresponding to 60% finer.
• D30 = Size of particle corresponding to 30% finer.
• D10 = Size of the particle corresponding to 10% finer.

The size D10 is some times called effective size. The value of Cu is nearly equal to unity for a uniformly of poorly graded soil. The value of Cc is more than 1.0 but less than 3.0 for well-graded soil. Cu is greater than 6 for sands.