Particle size distribution

1. Particle size distribution
curve

2. Curve A- well graded soil (good representations of all type particle)
Curve B- uniformly graded soil (most of the particle are in same size)
Curve c- well graded sand
Curve E- gap graded soil (some intermediate particle are missing)

3. Uniformity coefficient (Cu):
Uniformity coefficient is a measure of particle-size
range and is given by the ratio of D60 and D10 sizes:
Cu = D60 /D10
Uniformly grade soil, Cu is nearly unity.
For well graded soil ,
cu > 4 for gravel.
cu = 6 for sand.

4. COEFFICIENT OF CURVATURE (cc):
The shape of particle-size
curve is represented by the Coefficient of
curvature cc, given by
Cc = (D30 )2/(D10 x D60 )
For well graded soil ,
cc must between 1 to 3.

6. For coarse grained soil, certain particle size such as
D 10 ,D 30 and D 60 .
D 10 – Represents a size, in mm such that
10%of particles are finer than this size.
It is called as effective diameter or
effective size.
D 30 – Represents a size, in mm such that
30%of particles are finer than this size.
D 60 – Represents a size, in mm such that
60%of particles are finer than this size.