AtterbergLimits

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ME 420L/ME 506L: Soil Mechanics Laboratory

Lab No. 5: Atterberg Limits

ASTM D4318

Note: This lab instruction has been prepared by using the following Soil Mechanics Laboratory Manual:

Das, B. M. (2009). Soil Mechanics Laboratory Manual. 7th

Edition, Oxford University Press Inc, New York.

Introduction: The moisture content (%) at which the cohesive soil will pass from a liquid state

to a plastic state is called the liquid limit of the soil while the plastic limit is the moisture content

at which the soil changes from the plastic to a semisolid state or the moisture content (%) atwhich a thread of soil will just crumble when rolled to a diameter of 1/8 in (3.18 mm) and

similarly changing from the semisolid state to a solid state is referred to as the shrinkage limit.

Liquid Limit

1. Determine the mass of three moisture cans (M1) (Figure 1).

Figure 1: Moisture can

2. Put about 250 g of dry soil passing No. 40 sieve into an evaporating dish adding waterand mixing the soil to form a uniform paste.

3. Place a portion of the paste in the brass cup of the liquid limit (Casagrande) device(Figure 2). Use a spatula to smoothen the surface of the soil in the cup such that the

maximum depth of the soil is about 8 mm.

Figure 2: Liquid limit device

4. Cut a groove along the center line of the soil pat in the cup using a grooving tool.5. Turn the crank at a rate of about 2 revolutions per second. Count the number of blows

(N), for the groove in the soil to close through a distance of in ( 13 mm) between 25

and 35 blows. Collect a moisture sample from the soil in the cup in a moisture can. Closethe cover of moisture can and determine the mass of the can plus the moist soil (M 2).

Clean cup with paper towels.

6. Add more water to the soil paste in the evaporating dish and mix thoroughly. Repeatsteps 3, 4, and 5 to get a groove closure of in ( 13 mm) between 20 and 25 blows.

7. Add more water to the soil paste in the evaporating dish and mix thoroughly. Repeatsteps 3, 4, and 5 to get a groove closure of in ( 13 mm) between 15 and 20 blows.


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ASTM D4318




8. Put the three moisture cans in the oven to dry to constant masses (M3).

Calculations

Determine the moisture content for each of the three trials as:

(%) =23

31 100 (1)

Plot flow curve. Find liquid limit and flow index. Compare the results with one-point liquid limit

test.

Plastic Limit

1. Put approximately 20 g of dry soil sample passing through sieve No. 40 into a porcelain-evaporating dish, then mix with water thoroughly.

2. Determine the mass of moisture can in grams as (M1).3. Prepare several ellipsoidal-shaped soil masses by squeezing the soil with your fingers

from step 2.

4. Roll one of the ellipsoidal-shaped soil masses on a glass plate (Figure 3) using your palmof your hand at one complete backward and one complete forward motion making 80

strokes per minute

Figure 3: Glass plate

5. When the rolling thread reaches in (3.18 mm), break it up into several small pieces andsqueeze it with the fingers to form an ellipsoidal mass again

6. Repeat steps 4 and 5 until the thread crumbles into several pieces when it reaches adiameter of in (3.18 mm).

7. Collect the small crumbled pieces in the moisture can and cover the can.8. Take the other ellipsoidal soil masses formed in step 3 and repeat step 4 through 7.9. Determine the mass of the can plus the wet soil (M2) in grams and then place the can in

the oven (remove the cover) for about 24 hours (Figure 4).

10.Remove the can from the oven and determine the mass of the can plus the dry soil (M3) ingrams.


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Figure 4: Moisture cans in the oven

Calculations

=

=2 3

3 1 100 (2)

PI = LL-PL (3)

Note

Your lab report should include:

1. A complete description of the soil2. Applications of Atterberg limits3. Different methods used to determine Atterberg Limits4. Application(s) of liquidity index5. The relationship between PI and volume change6. Sources of errors and the effect of them on Atterberg limits7. Comparison of the obtained results with the typical values8. Type of the clay mineral based on the Atterberg limits9. Relationship between the liquid limit and specific surface

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