Explanation:

Particle Size classification:

This classification of soils is done on the basis of particle size composition. According to which soil may be termed as clay, silt, sand, gravel, cobbles and boulders.

I.S. Classification (Grain size distribution):

(i) Clay = d < 2μ 

(ii) Silt = 2μ < d < 75μ 

• Fine silt = 2μ < d < 10μ 
• Medium silt = 10μ < d < 20μ 
• Coarse silt = 20μ < d < 75μ 

(iii) Sand = 75μ < d < 4.75 mm

• Fine sand = 0.075 mm < d < 0.425 mm
• Medium sand = 0.425 mm < d < 2 mm
• Coarse sand = 2 mm < d < 4.75 mm

(iv) Gravel = 4.75 mm < d < 80 mm

• Fine gravel = 4.75 mm < d < 20 mm
• Coarse gravel = 20 mm < d < 80 mm

(v) Cobbles = 80 mm < d < 300 mm

(vi) Boulders = d > 300 mm