Uniformity coefficient of a soil ((C_u)) is given by (C_u=D₆₀/D₁₀)

Uniformity coefficient of well-graded soil

Definition:
The uniformity coefficient (UC) is a measure of the degree of particle size distribution in a soil sample. It is defined as the ratio of the particle size corresponding to 60% finer to that corresponding to 10% finer, i.e., UC = D60/D10.

Explanation:

- Well-graded soil is a soil in which the range of particle sizes is broad and the soil contains a variety of particle sizes.
- The uniformity coefficient of well-graded soil is greater than 6, which means that the range of particle sizes is very broad.
- A uniformity coefficient of less than 2 indicates that the soil is poorly graded, and the range of particle sizes is narrow.
- A uniformity coefficient between 2 and 6 indicates that the soil is moderately well-graded, and the range of particle sizes is moderate.
- The particle size distribution of soil affects its mechanical properties, such as shear strength, compressibility, and permeability.
- Well-graded soils generally have good engineering properties due to the presence of a variety of particle sizes, which can provide good interlocking between particles.
- However, the presence of large particles in well-graded soil can also lead to instability and settling, particularly in fine-grained soils.

Conclusion:

In summary, the uniformity coefficient of well-graded soil is greater than 6, indicating a broad range of particle sizes. The particle size distribution of soil affects its mechanical properties and should be considered in engineering design and construction.