Uniformity Coefficient

on . Posted in Geotechnical Engineering

Uniformity coefficient, abbreviated as \(C_u\), also called coefficient of uniformity, a dimensionless number, classifies a soil as well graded or poorly graded.  It is a measure used in geotechnical and civil engineering to describe the particle size distribution of a granular material such as soil, sand, or gravel.  It is an important parameter in soil mechanics and plays a significant role in various engineering applications, including the design of foundations, embankments, and drainage systems.

Key Points about Uniformity coefficient

  • A higher uniformity coefficient indicates a wider range of particle sizes in the material, suggesting that the material is less uniform in terms of particle size distribution.
  • A lower uniformity coefficient indicates a more uniform distribution of particle sizes.

Engineers use the uniformity coefficient to assess the suitability of a granular material for various construction purposes.  Materials with a high CU may have a wide range of particle sizes, which can affect their compaction properties, permeability, and stability in construction projects.  In contrast, materials with a lower CU are often preferred for certain applications because they are more uniform and predictable in their behavior.

 

Uniformity Coefficient formula

\( C_u =   D_{60} \;/\; D_{10} \)     (Uniformity Coefficient)

\( D_{60} =   C_u  \;  D_{10}   \)

\( D_{10} =   D_{60} \;/\; C_u \)

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

 

P D Logo 1

Tags: Coefficient Soil