Question

The uniformity coefficient of soil is calculated as

• A. \(D_{60} \times D_{10}\)
• B. \(D_{60} + D_{10}\)
• C. \(D_{60} - D_{10}\)
• D. \(D_{60} / D_{10}\)

Hint:

Gradation criteria:
Well-graded gravel: $C_u > 4$ and $1 \le C_c \le 3$.
Well-graded sand: $C_u > 6$ and $1 \le C_c \le 3$.
Uniform soil: $C_u \approx 1$.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
The particle size distribution curve of soil is quantified using shape parameters that define its gradation and particle size spread.
Key Formula or Approach:
\[ C_u = \frac{D_{60}}{D_{10}} \]
\[ C_c = \frac{(D_{30})^2}{D_{60} \times D_{10}} \]

Step 2: Detailed Explanation:
In soil particle gradation analysis:
- \(D_{60}\) is the grain diameter such that 60% of the total soil mass is finer than this size.
- \(D_{10}\) is the effective grain size such that 10% of the soil mass is finer.
The Uniformity Coefficient \(C_u\) is defined as the ratio:
\[ C_u = \frac{D_{60}}{D_{10}} \]
A large \(C_u\) indicates a well-graded soil containing a wide range of grain sizes.

Step 3: Final Answer:
Hence, the uniformity coefficient is calculated as \(D_{60} / D_{10}\), matching option (D).