Coefficient of Uniformity (Cu) Calculator

The Coefficient of Uniformity (Cu) is a key parameter in particle size analysis, commonly used in the fields of geotechnical engineering, soil science, and sedimentology. It quantifies the range of particle sizes in a sample, providing insight into the uniformity or variability of the material.

Historical Background

The Coefficient of Uniformity has been widely used to characterize the gradation of soils, especially in the design and analysis of soil for foundations, filtration systems, and other civil engineering applications. It is typically used in conjunction with the Coefficient of Gradation (Cu) to classify soils based on their particle size distribution.

Calculation Formula

The formula to calculate the Coefficient of Uniformity (Cu) is:

\[ Cu = \frac{D60}{D10} \]

Where:

• \( D60 \) is the diameter at the 60th percentile of the cumulative particle size distribution.
• \( D10 \) is the diameter at the 10th percentile of the cumulative particle size distribution.

Example Calculation

If the diameter at the 60th percentile (D60) is 1.2 mm and the diameter at the 10th percentile (D10) is 0.5 mm, the calculation for Cu would be:

\[ Cu = \frac{1.2}{0.5} = 2.4 \]

Importance and Usage Scenarios

The Coefficient of Uniformity is an important indicator of the uniformity of particle sizes in materials such as sand, gravel, and other granular soils. It helps engineers and geologists assess the suitability of materials for specific construction applications. For example, a high Cu value indicates a material with a broad range of particle sizes, which might be better for drainage or filtration. A lower Cu value suggests more uniformity in particle size, often preferred in applications like concrete.

Common FAQs

1. What does a high Coefficient of Uniformity mean?

   • A high Cu value indicates a wide range of particle sizes in the sample, which may be desirable in applications like drainage, where both large and small particles are needed.

2. What is the significance of D60 and D10?

   • D60 and D10 are key points on a particle size distribution curve, representing the diameters at which 60% and 10% of the sample, respectively, consists of smaller particles. These values help define the uniformity of the material.

3. How does Cu affect the engineering properties of soil?

   • A higher Cu value often means the material is well-graded, with a mix of fine and coarse particles, which can improve compaction and stability. A lower Cu value typically suggests a more uniform material, which might have better strength in certain applications.

This calculator helps quickly determine the Coefficient of Uniformity for soil and other granular materials, assisting professionals in selecting suitable materials for construction and engineering projects.