ENGINEERING – GEOTECHNICAL ENGINEERING CALCULATOR
Uniformity Coefficient
A precise tool.
What is the Uniformity Coefficient & How does it work?
Grain‑size distribution curves are constructed from sieve analysis data, where D10, D30 and D60 represent the particle diameters at which 10 %, 30 % and 60 % of the soil mass, respectively, are finer by weight. These characteristic diameters are fundamental for describing the gradation of granular soils.
The **coefficient of uniformity** (Cu) quantifies the spread of particle sizes. A larger Cu indicates a well‑graded soil with a wide range of grain sizes, while a value close to 1 suggests a uniform (poorly graded) soil.
The **coefficient of curvature** (Cc) evaluates the shape of the gradation curve between D10, D30 and D60. Values of Cc between 1 and 3 generally indicate a well‑graded soil, whereas values outside this range suggest a gap‑graded or uniformly graded material.
C_{u}=frac{D_{60}}{D_{10}}
Cu = coefficient of uniformity
C_{c}=frac{D_{30}^{2}}{D_{10},D_{60}}
Cc = coefficient of curvature
Parameters
Result
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Frequently Asked Questions
What is the formula for calculating the coefficient of uniformity (Cu)?
The coefficient of uniformity (Cu) is calculated as Cu = D60 / D10.
How does a high coefficient of uniformity indicate soil gradation?
A high Cu value indicates a well-graded soil with a wide range of grain sizes.
What does a low coefficient of uniformity (Cu close to 1) suggest about the soil?
A low Cu value suggests a uni-graded soil with particles of similar size.
Can you explain what D10, D30, and D60 represent in sieve analysis?
D10, D30, and D60 are particle diameters at which 10%, 30%, and 60% of the soil mass is finer by weight.
Why is the coefficient of uniformity important in soil engineering?
Cu helps describe the gradation of granular soils, which is crucial for various engineering applications like foundation design.
What are the typical ranges for Cu values in different types of soils?
Well-graded soils typically have a Cu value between 4 and 6, while poorly graded soils can have Cu values less than 4 or greater than 6.
How do I interpret the results of the coefficient of uniformity calculation?
A higher Cu indicates better drainage and lower potential for erosion, while a lower Cu suggests more uniform particle sizes which may affect compaction properties.
Results are for informational purposes only and do not constitute professional advice.