ATTERBERG LIMIT TESTS – LIQUID AND PLASTIC LIMITS
Group 1
Jarred L. Neal
John Brdaric
Eric Murnyack
Lab date: 09/27/01 and 09/20/01
Submitted date: 10/04/01
Purpose:
The purpose of the Atterberg Limit Lab was to calculate different properties of a
certain soil type. In the lab there were experiments ran to find the liquid limit, plastic
limit, and the plasticity index. These experiments were all based on the amount of water
in the soil. The Liquid limit is the moisture content at the division between the liquid and
plastic state, whereas, the plastic limit is themoisture content at the division between the
plastic and semisolid state. The plasticity index is the numerical difference between the
liquid limit and the plastic limit. This indicates the range of water content in which the
soil remains in the plastic state.
Scope:
The soil that was used in this experinment was soil that passed the 40 sieve. The
soil was then air died and prepared for the liquid and plasitic tests. The Casagrande
Liquid Limit Device was used during this experiment. The liquid and plastic limits were
determined in accordinance wit hthe ASTM D 4318 and ASSHTO T89 and T90.
Equipment:
Equipment:
A.
B.
C.
D.
E.
F.
G.
H.
I.
J.
Spatula, Small
Liquid Limit Tool
Spoon
Liquid Limit Device
Graduated Cylinder 50ml
Guth Wash Bottle
Small Metal Containers
Large Metal Containers
Mortar
Glass Plate
Procedure:
Liquid Limit
Obtain a soil sample and place in the brass cup of the liquid limit device, cut a
standard groove from the back of the cup to the front, and count the number of drops of
the device that are required to close the groove. If the number of drops is less than 20 or
more than 30, the water content of the soil sample is adjusted and the procedure repeated
until the number of drops is between 20 and 30 drops, at which time the water content of
the soil is determined. The liquid limit is computed using an equation involving the
number of drops required to close the groove and the associated water content of the soil.
Two such determinations are done, and an average value is taken as the liquid limit.
~ The procedure in the preceding paragraph, is denoted by ASTM as the “OnePoint Liquid Limit---Method B” and was obtained from “Soil Properties”; Cheng Liu and
Jack B. Evett.
Plastic Limit
Roll another portion of the soil sample between the fingers and a roughed glass
rolling surface until a 1/8-inch diameter thread is obtained. Break the resulting specimen
into smaller pieces, compress and repeat the rolling process to a diameter of 1/8-inch. This
procedure is repeated until the mass crumbles and can no longer be made into threads.
The plastic limit is now assumed to be reached and the water content (which is the plastic
limit) is to be determined by the equation: {[weight of water/weight of dry soil] * %}
Data Sheets:
Type of Test =
Test Number
# of drops =
weight of sample + tare wet =
weight of sample + tare dry =
Tare =
LL
1
41
26.43
23.89
15.91
LL
2
30
27.2
24.12
15.63
LL
3
10
29.55
25.56
15.78
drops
g
g
g
Type of Test =
Test Number
weight of sample + tare wet =
weight of sample + tare dry =
Tare =
PL
4
17.49
17.17
15.73
PL
5
17.46
17.17
15.77
PL
6
17.19
16.95
15.69
g
g
g
Sample Calculations:
Liquid Limit
Weight of water = (wt. Sample + tare wet) – (wt. Sample + tare dry)
Wt. Of water = 26.43-23.89 = 2.54 grams
Weight of dry soil = (wt. Sample + tare dry) – tare
Wt. Of dry soil = 23.89-15.91 = 7.98 grams
Water Content = ( wt.water  wt.drysoil )  100
Water Content = (2.54  7.98)*100= 31.8%
Plastic Limit
Weight of water = (wt. Sample + tare wet) – (wt. Sample + tare dry)
Wt. Of water =17.49-17.17= 0.32 grams
Weight of dry soil = (wt. Sample + tare dry) – tare
Wt. Of dry soil = 17.17-15.73= 1.44 grams
Water Content = ( wt.water  wt.drysoil )  100
Water Content = (0.32  1.44)*100= 22.2%
The liquid limit was found by graphing the water content in percent of dry weight versus
the number of blows of a liquid limit device. The limit is found by drawing a line from
the 25 blow line straight over to the water content axis. This percent is then taken to be
the liquid limit.
Liquid Limit
LL=33.7%
The plastic limit is found by taking the average of the plastic limit water contents.
Plastic Limit
PL= (22.2% + 20.7% + 19.0%)/3= 21%
The Plasticity index is found by subtracting the Plastic Limit from the Liquid limit.
Plasticity Index
PI = 12.7%
Calculated Test Results:
Type of Test =
Test Number
# of drops =
weight of sample + tare wet =
weight of sample + tare dry =
weight of water =
Tare =
Wt. Of Dry Soil =
Water content =
LL
1
41
26.43
23.89
2.54
15.91
7.98
31.8
LL
2
30
27.2
24.12
3.08
15.63
8.49
36.3
LL
3
10
29.55
25.56
3.99
15.78
9.78
40.8
drops
g
g
g
g
g
%
Type of Test =
Test Number
weight of sample + tare wet =
weight of sample + tare dry =
weight of water =
Tare =
Wt. Of Dry Soil =
Water content =
PL
4
17.49
17.17
0.32
15.73
1.44
22.2
PL
5
17.46
17.17
0.29
15.77
1.40
20.7
PL
6
17.19
16.95
0.24
15.69
1.26
19.0
g
g
g
g
g
%
Test Results
Liquid Limit 33 %
Plastic Limit 21%
Plasticity Index 13%
Evaluation:
Throughout the lab a variety of tests were ran on the soil type. Values were
obtained for the liquid and plastic limits and the plasticity index. With this information it
was possible to come to the conclusion that the soil was classified as a lean clay soil. The
reults were compared to other groups or published data. The group chose to check with
other groups because the soil was tested in the same atmosphere and with the same
equipment. Although the test was performed with the same equipment and in the same
atmosphere, differences in the results still appeared. (Chart below)
With an experiment there is going to be error in the final results. Majority of all error
amounts from human error. For example, the liquid limit device may not have been
operated correctly. Two drops per second at a constant rate was the instructions. But this
may varied in each group, throwing off the final results. Also the amounts of water that
was added to the soil may not have been recorded correctly. This type of error also goes
for the weight of the soil. Amounts of soil could have been lost in the act of mixing,
resulting in ratio of water to soil being identified wrong. As you can see there are many
instances were error could have entered the experiment, throwing off the results, and
giving us the difference in the results by group.
Group 1
Group 4
Group 6
Group 7
Liquid Limit
36%
41%
39%
36%
Plastic Limit
21%
24%
23%
26%
Plasticity Index
15%
17%
16%
10%
Work Cited:
1. “Essentials of Soil Mechanics and Foundations,” McCarthy, David, Fifth Edition
© 1998 Prentice Hall.
2. “Soil Properties,” Liu, Cheng and Evett, Jack, Fourth Edition © 2000, Prentice
Hall.
3. Manion, William P. (wmanion@maine.edu). "Soil Mechanics Laboratory Course
CIE 366." University of Maine, Civil and Environmental Engineering
Department, Orono, Maine. http://www.umeciv.maine.edu/cie366/.