**Uniformity coefficient(Cu)**

The uniformity coefficient is a measure of particle size range and given by the ratio of D_{60} and D_{10} size of particles. It is denoted by C_{u}.

**Thus, C _{u} = D_{60}/D_{10}**

Where,

- D
_{60}= Size of the particle corresponding to 60% finer and, - D
_{10}= 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:

**C _{c} = (D_{30})2/D_{60}.D_{10}**

Where,

- D
_{60}= Size of the particle corresponding to 60% finer. - D
_{30}= Size of particle corresponding to 30% finer. - D
_{10}= Size of the particle corresponding to 10% finer.

The size D_{10} is some times called effective size. The value of C_{u} is nearly equal to unity for a uniformly of poorly graded soil. The value of C_{c} is more than 1.0 but less than 3.0 for well-graded soil. C_{u} is greater than 6 for sands.

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