Soil mechanics experiments

1. 1
Atterberg Limits =
Consistency limits =
Limits of consistency

2. 2
As water is added to a dry plastic soil, the remolded mixture will
eventually have the characteristics of a liquid. In changing
from a solid to a liquid, the material first becomes a semisolid
and then a plastic.
The points at which each of these changes occur are known as the
Atterberg Limits.
Atterberg Limits
• Atterberg Limits are defined by the Shrinkage Limit (SL), Plastic
Limit (PL), Liquid Limit (LL), and Plastic Index (LL) – (PL) = PI
• Atterberg Limits are determined on minus 40 materials

3. 3
Atterberg Limits
Liquid Limit, LL
Liquid State
Plastic Limit, PL
Plastic State
Shrinkage Limit, SL
Semisolid State
Solid State
Dry Soil
Fluid soil-water
mixture
Increasing
water
content

4. Atterberg Limits 4
Plasticity
• Primary form of classification for cohesive
soils
• Soils can be in any one of 4 physical states
(based on water content)
Water Content
Plastic Liquid
Semi-
solid
Solid

5. Atterberg Limits 5
Atterberg Limits = these are water/moisture
contents of the soil mass as it passes from stage to
stage
• Atterberg limits are the points at which the
soil changes phase
Liquid
Limit
Plastic
Limit
Shrinkage
Limit
Water Content
Plastic Liquid
Semi-
solid
Solid

6. Atterberg Limits 6
SOLID
STATE
SEMI-SOLID
STATE
PLASTIC
STATE
LIQUID STATE
LIQUID
LIMIT
(LL)
WATER
CONTENT
PLASTIC LIMIT
(PL)
PLASTICITY
INDEX
(PI)
VOLUME CHANGE
SHRINKAGE LIMIT
(SL)
CONSISTENCY DIAGRAM RELATING
WATER CONTENT AND VOLUME CHANGE
Minus 40 materials = that pass through
the No. 40 sieve or 0.425 mm opening

7. Atterberg Limits 7
Atterberg Limits
• The Shrinkage Limit (SL) is
the water content at which a
further reduction in water
does not cause a decrease in
the volume of the soil mass.
• This defines the limit
between the solid and
semisolid states of
consistency.
SOLID
STATE
SEMI-SOLID
STATE
PLASTIC
STATE
LIQUID STATE
LIQUID
LIMIT
(LL)
WATER
CONTENT
PLASTIC LIMIT
(PL)
PLASTICITY
INDEX
(PI)
VOLUME CHANGE
SHRINKAGE LIMIT
(SL)
CONSISTENCY DIAGRAM RELATING
WATER CONTENT AND VOLUME CHANGE

8. TDP 2 - Soils Eng. Atterberg Limits 8
Atterberg Limits
• The Plastic Limit (PL) is the
water content corresponding
to an arbitrary limit between
the plastic and semisolid
states of a soil’s consistency.
• This is the the water content
at which a soil will just begin
to crumble when rolled into a
thread approximately ⅛” in
diameter.
SOLID
STATE
SEMI-SOLID
STATE
PLASTIC
STATE
LIQUID STATE
LIQUID
LIMIT
(LL)
WATER
CONTENT
PLASTIC LIMIT
(PL)
PLASTICITY
INDEX
(PI)
VOLUME CHANGE
SHRINKAGE LIMIT
(SL)
CONSISTENCY DIAGRAM RELATING
WATER CONTENT AND VOLUME CHANGE

9. Atterberg Limits 9
Plastic Limit
Water content at
which 1/8”
thread can be
rolled and just
begins to
crack

10. Atterberg Limits 10
Atterberg Limits
• The Liquid Limit (LL) is
the water content
corresponding to an arbitrary
limit between the liquid and
plastic states of a soil’s
consistency.
• This is the the water content
at which a pat of soil, cut by
a groove 5/64” wide, will flow
together for a distance of 1/2”
under the impact of 25 blows
in a standard liquid limit
apparatus.
SOLID
STATE
SEMI-SOLID
STATE
PLASTIC
STATE
LIQUID STATE
LIQUID
LIMIT
(LL)
WATER
CONTENT
PLASTIC LIMIT
(PL)
PLASTICITY
INDEX
(PI)
VOLUME CHANGE
SHRINKAGE LIMIT
(SL)
CONSISTENCY DIAGRAM RELATING
WATER CONTENT AND VOLUME CHANGE

11. Atterberg Limits 11
Liquid Limit
Water content at
which groove
closes for
1/2”under 25
blows of cup
(Flows)

12. Atterberg Limits 12
Atterberg Limits
• The Plasticity Index (PI) is
the numerical difference
between the liquid limit and
the plastic limit.
PL
LL
PI 

SOLID
STATE
SEMI-SOLID
STATE
PLASTIC
STATE
LIQUID STATE
LIQUID
LIMIT
(LL)
WATER
CONTENT
PLASTIC LIMIT
(PL)
PLASTICITY
INDEX
(PI)
VOLUME CHANGE
SHRINKAGE LIMIT
(SL)
CONSISTENCY DIAGRAM RELATING
WATER CONTENT AND VOLUME CHANGE

13. 13
In determining the Atterberg Limits, the water content of the
material is measured at various levels determined by prescribed
test procedures.
Atterberg Limits

14. 14
Liquid Limit-LL
•Cone Penetrometer Method
•This method is developed by the
Transport and Road Research
Laboratory, UK.
•Multipoint test
•One-point test
•Casagrande Method
•Professor Casagrande standardized
the test and developed the liquid
limit device.
•Multipoint test
•One-point test

15. 15
Casagrande Method
N=25 blows
Closing distance =
12.7mm (0.5 in)
(Holtz and Kovacs, 1981)
•Device
The water content, in percentage, required to close a
distance of 0.5 in (12.7mm) along the bottom of the
groove after 25 blows is defined as the liquid limit

16. 16
Casagrande Method
N
w
•Multipoint Method

17. 17
Cone Penetrometer Method
•Device
(Head, 1992)
This method is developed
by the Transport and Road
Research Laboratory.

18. 18
Cone Penetrometer Method
•Multipoint Method
Water content w%
Penetration
of
cone
(mm)
20 mm
LL
The difference b/w the dial reading before and after (penetration)
are recorded. Test is repeated with increasing water content. The
LL is taken as moisture at which the cone penetrates 20 mm into
soil

19. 19
Plastic Limit-PL
The plastic limit PL is defined as the water content at which
a soil thread with 3.2 mm diameter just crumbles.
(Holtz and Kovacs, 1981)

20. 20
Shrinkage Limit-SL
(Das, 1998)
Soil volume: Vi
Soil mass: M1
Soil volume: Vf
Soil mass: M2
)
100
)(
(
M
V
V
)
100
(
M
M
M
(%)
w
(%)
w
SL
w
2
f
i
2
2
1
i
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

 

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



 


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