Answered Classification of Soil based on size of Particles

Dnyan Deshmukh

Staff member
As per IS 1498, Soils are classified as below

Boulder -Average size is more than 300 mm.

Cobble - Smaller than 300 mm and bigger than 80 mm.

Gravel -Smaller than 80 mm and bigger than 4.75 mm.

Gravels are further classified as

Coarse - For sizes between 80 mm to 20 mm.
Fine -For sizes between 20 mm to 4.75 mm.

Sand -smaller than 4.75 mm and bigger than 75 micron

Sands are further classified as

Coarse -Size between 4.75 mm and 2 mm.
Medium -Size between 2 mm and 425 micron.
Fine - Size between 425 micron and 75 micron.

Silt - It has sizes less than 75 micron, It does not show or show little plastic behavior due to moisture and exhibits little or no strength when air dried.

Clay - It also of size less than 75 micron, but it can be identified by its behavior. It can exhibit plastic properties within certain range of moisture / water, and also exhibits considerable strength when air dried.

Organic matters - They are in various sizes and stages of decomposition.