This ppt is more useful for Civil Engineering students. I have prepared this ppt during my college days as a part of semester evaluation . Hope this will help to current civil students for their ppt presentations and in many more activities as a part of their semester assessments. I have prepared this ppt as per the syllabus concerned in the particular topic of the subject, so one can directly use it just by editing their names.

1. Vishwakarma
Government
Engineering College,
Chandkheda
Name -Vekaria Darshil(150170106061)
Branch -Civil Engineering
Sub - GTAG
Sem -3
Topic –Classification of Soil

2. Types Of Soil
2

3. Soil Classification Systems
1. Particle Size Classification
2. Textural Classification
3. Unified Soil Classification Systems(USCS)
4. Indian Standard Classification System
(ISCS)
3

4. IS Classification of Grain Size
4

5. Soil classification of composite soils exclusively
based on Particle Size Distribution.
Most popular is the Triangular Classification of U.S.
Public Roads Administration.
Classification based on % of sand, silt and clay size.
More suitable for describing coarse grained soil.
Clay soil properties are less dependent on particle
size distribution.
5
Textural Classification

6. Textural Classification Chart
6
30% sand
30% silt
40% clay
Soil Type
Clay

7. Used to describe performance of soil when used for
pavement construction.
Not used to place a soil in a particular group.
It means rating the value of soil as a subgrade material
within its own group.
Higher the value of GI, poorer is the quality of material.
Group Index (GI)
7

8. Group Index of a soil depends on:
1. Amount of material passing 75 micron IS sieve.
2. Liquid Limit.
3. Plastic Limit.
Group Index (GI) determination
8Pranamesh Chakraborty

9.  First developed by Professor A.
Casagrande (1948) for the purpose of
airfield construction during World War
II.
 Afterwards, it was modified to enable the
system to be applicable to dams,
foundations, and other construction .
9
Unified Soil Classification System
USCS

10. Four Major Divisions
Course
Grained
Fine
Grained
Organic
Soil
Peat
10

11. Classification Groups
•The soil is classified into 15 groups.
•Each group is designated a symbol consisting of
two capital letters.
•The first letter is based on main soil type.
•The second letter is based on gradation and
plasticity .
11

12. Classification Group Symbols
Main Soil
Type
Prefix Subgroup Suffix
Classification
Group symbols
Gravel G
Well-graded
Poorly-graded
Silty
Clayey
W
P
M
C
GW
GP
GM
GC
Sand S
Well-graded
Poorly-graded
Silty
Clayey
W
P
M
C
SW
SP
SM
SC
Silt M
LL < 50%
LL > 50%
L
H
ML
MH
Clay C
LL < 50%
LL > 50%
L
H
CL
CH
Organic O
LL < 50%
LL > 50%
L
H
OL
OH
Peat Pt Pt
12

13. Unified Soil Classification System (Contd.)
Coarse-grained soils: Fine-grained soils:
NO.200
0.075 mm
Well or Poor Graded
based on Cu and Cc
50 %
NO. 4
4.75 mm
50%
wL >50
wL <50
Gravel (G) Sand (S) Silt (M) Clay (C)
Based on wL and IP
(Plasticity Chart)
For G, use W if Cu > 4 and 1<Cc <3
For S, use W if Cu > 6 and 1<Cc <3
13

14. Plasticity Chart
Below A-line, use M (Silt) or
O (Organic)
Above A-line, use C - Clay
High Plasticity use H - wL >50
Low Plasticity use L - wL <50
14
Silt (M)
Clay (C)
Organic (O)

15. Plasticity Chart
“The soil’s liquid limit (wL) after oven drying is less than 75 % of its liquid
limit before oven drying.” If the above statement is true, then it is Organic Soil
(OL or OH). Otherwise, it is Inorganic Soil (ML or MH)
15

16. Plasticity Chart
When IP and wL are in the hatched portion of the plasticity chart, the soil is
given dual symbol (CL-ML).
Soil possessing properties of more than one group are termed as boundary
soil and designated by dual group symbol.
16

17. Group Symbols and Group Names
Group Symbol Typical Name
GW Well-graded gravels.
GP Poorly-graded gravels.
GM Silty gravels.
GC Clayey gravels
SW Well-graded sands.
SP Poorly-graded sands.
SM Silty sands.
SC Clayey sands.
17

18. Group Symbol Typical Name
CL Inorganic clays of low plasticity.
ML Inorganic silts with slight plasticity.
OL Organic soil of low plasticity.
CH Inorganic clays of high plasticity.
MH Inorganic silts with high plasticity.
OH Organic soil of high plasticity.
Pt Peat.
Group Symbols and Group Names
18

19. Based on USCS system
Modifications are:
Fine grained soils subdivided into 3 groups (low,
intermediate and high plasticity) as against two
groups(low and high) in USCS.
wL <35=L, 35<wL <5o=I, wL >50=H
Thus, soil classified into 18 groups as against 15
in USCS. 19
Indian Standard Classification
System (ISCS)
IS:1498-1970

20. Plasticity Chart
High Plasticity use H - wL >50
Intermediate Plasticity use I – 35< wL >50
Low Plasticity use L - wL <35
20
Below A-line, use M (Silt) or
O (Organic)
Above A-line, use C - Clay

21. 21
Thank You