Classification of soils

Soil Classification Is done based on

“INDEX PROPERTIES”

“USEFUL FORCLASSIFICATION AND

IDENTIFICATION OF SOILS”

For Engineering purposes, soils may classified by the following system.

1.Particle size classification2. Textural classification3.Highway Research board classification4.Unified soil classification

& 5.IS classification

1.Particle size classification In this system,

soils are arranged according to grain size.The following terms are used to indicate grain size.

gravel Sand Silt and Clay

These terms are used only as designation of particles size, and do not signify the naturally occurring types.

The most commonly used Particle size soil classification systems are,1.U.S.Bureau of soil and public road administration system of U.S.

2.International soil classification system.

3.M.I.T classification 4.I.S classification based on M.I.T

classification

2. Textural classification

The natural soil are composed of different % of sand , silt ,and clay size particle.The classification of composite soils based on the particle size distribution is known as “Textural classification “. The best of these Textural classification is the triangular classification of US public road administration system shown in figure.

3.Highway Research board classification

It is based on both the particle size composition as well as the plasticity characters.

this system is mostly used for pavement construction.

soils are divided in to 7 primary groups, A-1, A-2 ……….. A-7

4.Unified soil classification

Soils are classified in to 4 major groups:1.coarse grained2.fine grained3.organic soils4.peat

IS classificationSoil are broadly divided in to 3 types: