Some commonly used measures are: a) Effective size :
It is the diameter in the particle size distribution curve (D10)
It is the diameter in the particle size distribution curve corresponding to 10% finer. (maximum size of the smallest 10% of the soil) b) Uniformity Coefficient:
It is the ratio of the maximum diameter of the smallest 60% to the effective size
Cu= D60/D10 A well graded soil will have
Cu > 4 for gravels Cu > 6 for sands **c) Coefficient of Curvature:** Cc = (D30)^2 / (D60 *D10)
D30 : Diameter corresponding the 30% finer
**e) Well-Graded Material** – Contains particles of a wide range of sizes. The smaller particles fill the spaces left between the larger The smaller particles fill the spaces left between the larger particles; therefore the soil has greater strength than a poorly
graded soil, and lower permeability. f) **Poorly – Graded Material** – Contains a large portion of uniformly sized particles. This particular soil has larger voids in its structure
and poor strength along with high permeability. |