Uniformity Coefficient

Uniformity coefficient, abbreviated as \(C_u\), also called coefficient of uniformity, a dimensionless number, classifies a soil as well graded or poorly graded. For the soil to be well graded for a given sample, the range must be between greater than 4 to 6.  If less than 4 it is classified as poorly graded.

 

Uniformity Coefficient formula

\(\large{ C_u =  \frac{ D_{60} }{ D_{10} }     }\)

Where:

Units	English	Metric
\(\large{ C_u } \) = uniformity coefficient	\(\large{dimensionless}\)
\(\large{ D_{10} } \) = is the sieve diameter (grain size) which there are 10% of particles go through.	\(\large{in}\)	\(\large{mm}\)
\(\large{ D_{60} } \) = is the sieve diameter (grain size) which there are 60% of particles go through.	\(\large{in}\)	\(\large{mm}\)