Atterberg Limit Tests - Liquid and Plastic Limits - Lab Report Example

The experiment involved the use of soil, which had passed through 40 sieves. After this, the soil was prepared for the liquid and plastic tests through air drying. The major apparatus used throughout the experimental process was The Casagrande Liquid Limit Device. Further, ASTM D 4318 and ASSHTO T89 and T90 were used as standards for determining the liquid and plastic limits.  

Method

Equipment

• Spatula, Small
• Liquid Limit Tool
• Spoon
• Liquid Limit Device
• Graduated Cylinder 50ml
• Guth Wash Bottle
• Small Metal Containers
• Large Metal Containers

Procedure:

Liquid Limit

A soil sample was acquired and placed in the brass cup of the liquid limit device. A standard groove was cut from the back of the cup to the front followed by counting the number of drops required required for closing the groove. The procedure was repeated and whenever water content was adjusted whenever the drops were <20 or <30 to achieve a number between 20 and 30.

Plastic Limit

A portion of the soil sample was rolled between the fingers and roughed glass rolling surface to achieve a 1/8-inch diameter thread limit. The resulting specimen was broken into smaller pieces, and compressed and the rolling process was repeated to a 1/8-inch diameter limit.  The procedure aforementioned was repeated to the point when the mass crumbled and could no longer allow for the formation of threads. At this point, the plastic limit was assumed to be reached.

Data sheet

PLASTIC LIMIT

1

2

3

4

Average

container no

mass of wet soil + container (m2) g

9.85

9.51

19.14

19.14

mass of dry soil + container (m3)  g

9.33

9

18.66

18.65

mass of container (m1)   g

6.65

6.54

16.36

16.36

mass of moisture (m2-m3)

0.52

0.51

0.48

0.49

mass of dry soil (m3 - m1)  g

2.68

2.46

2.3

2.29

moisture content w = (m2 - m3)/(m3 - m1)100%

19.403

20.7317

20.8696

21.3974

20.60043

Plastic limit

Plastic limit = taken as the average of the plastic limit water content  = 20.60%

LIQUID LIMIT              Test no

1

2

3

4

initial dial gauge reading

0

0

0

0

final dial gauge reading

average penetration

13.7

15.3

22.95

27.25

container no

3

88

89

79

mass of wet soil + container   g

12.74

37.87

24.56

27.31

mass of dry soil + container   g

11.39

32.28

19.33

24.06

mass of container

6.54

16.52

6.72

16.28

mass of moisture

1.35

5.59

5.23

3.25

mass of dry soil     g

4.85

15.76

12.61

7.78

moisture content %

27.8351

35.4695

41.475

41.7738

Arriving at the liquid limit involved putting a graph for water content in percent of dry weight against the number of drops of a liquid limit device.  The limit was found by drawing a line from the 25 drops line straight over to the water content axis.  From this, percentagecent was determined to be 36.8

Plasticity index

= 36.8% - 20.60% = 16.2%

Final results rounded off:

Liquid limit = 37%

Plastic limit = 21%

Plasticity index = 16%

Evaluation:

Throughout the lab, a variety of tests were run on the soil type.  Values were obtained for the liquid and plastic limits and the plasticity index.  With this information, it was possible to conclude that the soil was classified as lean clay soil (Cripps et al, 2006, 228).  Comparisons of the results were made to other groups in addition to published data. Despite all the groups using the same equipment, under the same atmospheric conditions, slight deviations were evidenced among the groups’ values.

The slight deviations can be attributed to errors arising in the final result with most of the errors arising from humans. For instance, operating the liquid limit device may have differed among the groups leading to differences in the final result. Further, the amounts of water used in the process might have not been recorded correctly due to parallax error. Some weight of the soil could have also been lost in the process of the mixing resulting in a wrong ratio of water to soil (Ranjan, 2006, 43).