Living Reference Work Entry

Encyclopedia of Engineering Geology

Part of the series Encyclopedia of Earth Sciences Series pp 1-2

Date: Latest Version

Coefficient of Uniformity


The coefficient of uniformity is a crude shape parameter and is a dimensionless ratio of the diameters of grains of sediment or particles of soil used to distinguish between well-graded and poorly graded coarse-grained soil using results from laboratory tests of grain size distribution.


Coarse-grained soil particles have grain sizes larger than 0.075 μm in engineering usage (ASTM 2011), which is the grain size at the boundary between silt and sand. The formula for the coefficient of uniformity, Cu, is ...

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