Soils are formed by weathering of rocks due to Mechanical disintegration or Chemical decomposition. When rock surface are exposed to atmosphere for considerable period of time,
( contineous heating and cooling of rock ) result in disintegrates or decomposes to form soil.
Formation of Soil also happens due to physical reaction and chemical reaction over the surface
1. Physical Disintegration
2. Chemical decomposition of rocks
Soil Classification is separation of soil into classes or groups each having similar characteristics and behaviour. Classification for engineering purpose should be based mainly on mechanical properties.
Like: Permeability, Stiffness, Strength etc.,
Classification based on Grain Size
- below 0.002mm are clay
- between 0.002 to 0.075mm are silt
- between 0.075 to 4.75mm are sand
- between 4.75 to 80mm are gravel size