Monday, 2 April 2018

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
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 a well graded soil.Cu is greater than 6 for sands.

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