Which property is assessed by the Coefficient of Uniformity (Cu)?

• A. Soil color
• B. Soil moisture content
• C. Soil gradation
• D. Soil density

Answer: (C)

The Coefficient of Uniformity (Cu) is specifically designed to measure the gradation of soil, which refers to the distribution of particle sizes within a soil sample. It is calculated as the ratio of the particle diameter at the 60th percentile to the particle diameter at the 10th percentile of the grain size distribution. A higher Cu value indicates a well-graded soil, meaning it has a good mix of particle sizes that contribute to better structure and stability. Conversely, a lower Cu suggests the soil may be poorly graded, meaning it consists of particles that are more uniform in size.

Soil color, moisture content, and density, while important properties in their own right, do not relate to the distribution of particle sizes and thus are not assessed by the Coefficient of Uniformity. This focused definition of the Cu underscores its role in understanding how soil will behave in engineering and construction applications, making it a crucial factor in soil analysis.