DETERMINATION OF SOIL CONSISTANCY LIMITS A. Casagrande method: PL, LL B. Cone penetrometer method: CPPL, CPLL

1. WELCOME TO OUR
PRESENTATION
SUBMITTED TO
DR. MD. ZAINAL ABEDIN
PROFESSOR
DEPT. OF FARM STRUCTURE &
ENVIRONMENTAL
ENGINEERING
SUBMITTED BY
1605085
1605087
1605088
1605090
1605100

2. DETERMINATION OF SOIL
CONSISTANCY LIMITS:
A. Casagrande method: PL, LL
B. Cone penetrometer method: CPPL, CPLL

3. A. DETERMINATION OF THE LIQUID LIMIT
OF SOIL BY CASAGRANDE METHOD
Objectives: To determine the liquid limit of soil.
Theory:
The liquid limit is the water content at which the soil will flow under its
own weight. In liquid limit the soil behaves practically like a liquid, but
has small shear strength. It flows to close the groove is just 25 blows in
Casagrande’s liquid limit device. As it is difficult to get exactly 25 blows
in a test, 3 to 5 tests are being conducted, and the number of blows (N)
required in each test is determined. A semi-log plot is drawn between
log(N) and the water content (w). The liquid limit is the water content
corresponding to N = 25 blows, as obtained from the plot.

4. Apparatus Required:
1. Casagrande apparatus, 2. Grooving tools of both standard and
ASTM types, 3. Oven, 4. Spatula, 5. Evaporating dish or glass sheet,
6. 425 µ IS sieve, 7. Balance and 8. Wash bottle etc.


5. Methodology
1) The drop of the cup of the liquid limit device was adjusted
by releasing the two screws at the top and by using the
handle of the grooving tool or a gauge. The drop should be
exactly 1 cm at the point of contact on the base. The screw
was tightened after adjustment.
2) About 120gm of the air-dried soil sample passing 425 µ is
sieve was taken.
3) The sample was mixed thoroughly with distilled water in an
evaporating dish or a glass plate to form a uniform paste.
Mixing should be continued for about 15 to 30 minutes, till a
uniform mix was obtained.
4) The mix was kept under humid conditions for obtaining
uniform moisture distribution for sufficient period. For
some fat clay this maturing time may be up to 24 hours.

6. Methodology(cont.)
5) A portion of the matured paste was taken and remixed it thoroughly. It
was placed in the cup and leveled it by a spatula to have a maximum
depth of the soil as 1 cm at the point of the maximum thickness.
6) A groove was cut in the sample. The grooving tool was drawn through
the paste in the cup along the symmetrical axis, along the diameter
through the center line of the cam. The tools were held perpendicular
to the cup.
7) The handle of the device was turned at a rate of 2 revolutions per
second. The number of blows was counted until the two halves the
soils specimen come in contact at the bottom of the groove along a
distance of 12 mm due to flow and not by sliding.
8) A representative specimen of the soil was collected by moving spatula
width-wise from one edge to the other edge of the soil cake, at right-
angles to the groove. The specimen was placed in a container for
moisture content determination. The water content was determined.

7. Methodology(cont.)
9) The retaining soil was removed from the cup. It was mixed
with the soil left in the evaporating dish.
10) The water content of the mix was changed in the
evaporating dish, either by adding more water if the water
content was to be increased, or by kneading the soil, if the
water content was to be decreased. In no case, the dry soil
should be added to reduce the water content.
11) Steps 4 to 10 were repeated and the number of blows (N)
and the water content were determined in each case.
12) The flow curve between log(N) and w was drawn, and the
liquid limit corresponding to N = 25 blows was determined.

8. Fig: Liquid limit of soil by casagrande
method
Fig: Casagrande apparatus

9. Sl.
No.
Observations and Calculations
Replications
1 2 3 4 5
Observations
1. No. of blows (N) 32 30 24 20 16
2. Can No. 𝑹 𝟏 𝑹 𝟐 𝑹 𝟑 𝑹 𝟒 𝑹 𝟓
3. Weight of the empty Can (W1) 21.3 21.3 21.3 21.3 21.3
4. Weight of Can + Wet soil (W2) 28.7 32.0 24.3 32.0 25.7
5. Weight of Can + Dry soil (W3) 27.7 30.0 23.7 29.1 24.1
Calculation
6. Water content, 𝒙 =
𝑾 𝟐−𝑾 𝟑
𝑾 𝟑−𝑾 𝟏
× 𝟏𝟎𝟎 15.6 22.0 25.0 37.2 57.0
Data sheet
Result: At liquid limit ,water content was 29%

10. B. Determination of the Plastic Limit of
soil by Casagrande Method
Objectives:
To determine the plastic limit of a soil specimen
Theory:
The plastic limit of a soil is the water content of the soil below
which it ceases to be plastic. It begins to crumble when rolled
into threads of 3 mm diameter.

11. Apparatus required:
1. Glass plate,
2. Out side calipers,
3. Oven,
4. Balance,
5. Spatula and
6. Can etc.

12. Methodology:
1. 30 gm of air-dried soil was taken from a thoroughly
mixed sample of the soil passing 425 sieve.
2. The soil was mixed with distilled water in on a glass
plate to make it plastic enough to shape into a small
ball.
3. The plastic soil mass was left for some time for
maturing.
4. About 8 gm of the plastic soil was taken and it was rolled
with fingers on a glass plate. The rate of the rolling
should be about 80 to 90 strokes per minutes to form a
thread of 3 mm diameter, counting one stroke when the
hand moves forward and backward to the starting point.

13. Methodology(cont.):
5. If the diameter of the thread becomes less than 3mm
without cracks, it shows that the water content is
more than the plastic limit. The soil was kneaded to
reduce the water content and it was rolled again into
thread.
6. The process of alternate rolling and kneading was
repeated until the thread crumbled, and the soil could
no longer be rolled into thread. The pieces of the
crumble soil thread was collected in a moisture
content container.
7. The procedure was repeated at least twice more with
fresh sample of plastic soil each time

14. Data sheet:
Sl.
No. Observations and Calculations
Replications
1 2 3 4 5
Observations
1. Can No. 𝑹 𝟏 𝑹 𝟐 𝑹 𝟑 𝑹 𝟒 𝑹 𝟓
2. Weight of the empty can, W1
21.3 21.3 21.3 21.3 21.3
3. Weight of Can + wet soil, W2
28.7 32.0 24.3 32.0 25.7
4. Weight of can + dry soil, W3
27.7 30.0 23.7 29.1 24.1
Calculation
5. Water content, 𝑥 =
𝑊2−𝑊3
𝑊3−𝑊1
× 100 15.6 22.0 25.0 37.2 57.0
Result: Average water content is 31.36%

15. C. Determination of the plastic and liquid limits of
soil by cone-penetrometer method
Objective:
To determine the cone-penetrometer plastic limit and liquid limit of
soil
Theory:
Cone penetrometer consists of a stainless steel cone having an apex
angle of 300
± 10
and a length of 35 mm. The cone is fixed at the
lower end of a sliding rod which is fitted with a disc at its top. The
total mass of the cone, sliding rod and the disc is 80𝑔𝑚 ± 0.05𝑔𝑚 . The
prepared soil paste is placed in a cup of 50 mm internal diameter and
50 mm height. The cup is placed below the cone and is allowed to
penetrate the soil for 5 seconds. If the penetration vs moisture content
curve is drawn, the water content at 20 mm penetration is the liquid
limit and the water content at minimum penetration is the plastic
limit.

16. Since it is difficult to obtain the penetration of 20 mm exactly, liquid limit
is determined from the equation given below
𝒘𝒍 =
𝒘 𝒚
𝟎. 𝟔𝟓 + 𝟎. 𝟎𝟏𝟕𝟓𝒚
Where, 𝑤𝑙 =liquid limit
y=penetration when water content is 𝑤 𝑦
𝑤 𝑦=water content when penetration y
Apparatus required:
1. Cone-penetrometer, 2.A cup of 50 mm internal diameter and 50 mm
height, 3. M.C. Can, 4. Balance, 5. Oven and 6. Spatula etc.

17. Methodology :
1. 500 gm of dried soil was taken in a glass plate and water was
put for make the paste.
2. The paste was kept for 30 minutes for maturing.
3. The cup of 50 mm internal diameter and 50 mm height was
filled with this paste so that there was no entrapped air. The
excess soil was removed and the cup surface was leveled.
4. The cup was placed below the cone penetrometer and the
cone was lowered gradually so as to just touch the surface of
the soil in the cup.
5. The graduated scale was adjusted as zero when cone touch the
cup surface.
6. The cone was released and penetration of soil was allowed for
5 seconds.

18. Methodology(cont.)
7. When the cone penetrated 20 mm exactly then soil sample was
taken for water content determination.
8. It is very difficult to get exactly 20 mm penetration, so the
penetration y was measured near 20 mm for the water content
wy. The process was repeated 4 to 10 times.
9. The liquid limit was calculated by using the equations.
10. In order to determine both the liquid and the plastic limits a
penetration vs moisture curve is drawn, the water content at 20
mm penetration is the liquid limit and the water content at
minimum penetration is the plastic limit.

19. Fig: Plastic and liquid limits of soil by
cone-penetrometer method
Fig: A cone penetrometer

20. Data sheet:
Sl.
No.
Observations and Calculations
Replications
1 2 3 4 5
Observations
1. Penetration, y 22.0 16.0 18.5 25.6 31.0
2. Weight of the empty can, W1 21.3 21.3 21.3 21.3 21.3
3. Weight of Can + wet soil, W2 27.9 31.0 28.7 24.3 32.0
4. Weight of can + dry soil, W3 27.6 30.1 27.7 23.7 29.1
Calculation
5. Water content,𝑤 𝑦 =
𝑊2−𝑊3
𝑊3−𝑊1
× 100
when penetration y mm
4.8 10 15.6 25.0 37.2
6. Liquid Limit,𝑤𝑙 =
𝑤 𝑦
0.65+0.0175𝑦
0.048 0.10 0.156 0.25 0.372
Result: From graph, we got water content 18% at liquid limit and 10% at
plastic limit

21. Precautions:
a) We have to use instruments very carefully.
b) All the measurement should be taken carefully.
c) Before using any instrument, we should know how
to use it.
d) After using the instrument, we should clean it.