Classification of soils

2. Soil Classification
Is done based on
“INDEX PROPERTIES”
“USEFUL FORCLASSIFICATION
AND
IDENTIFICATION OF SOILS”

3. For Engineering purposes, soils may classified
by the following system.
1.Particle size classification
2. Textural classification
3.Highway Research board
classification
4.Unified soil classification
&
5.IS classification

4. 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.

5. 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

8. 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.

10. 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

13. 4.Unified soil classification
Soils are classified in to 4 major groups:
1.coarse grained
2.fine grained
3.organic soils
4.peat

18. IS classification
Soil are broadly divided in to 3
types: