1. Atterberg Limits Liquid Limit & Plastic Limit of Soils
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2. Atterberg Limits Liquid Limit (LL) Plastic Limit (PL)
Shrinkage Limit (SL)
Moisture contents
Used for classification, Comparisons, identification.
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3. Figure 1: Soil States Solid Semi-Solid Plastic Liquid Plasticity Index
Shrinkage
Limit
Moisture Content
Low
High

4. Plasticity Index (PI) Numerical difference between LL and PL
PI = LL - PL
Range of water content
Figure 1
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5. Liquid Limit Test (Apparatus)
Porcelain mixing dish
Spatula
Grooving tool
Number 40 sieve
Figure 2 & Table 1
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6. Figure 2: Liquid Limit Device
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7. Table 1: Measurements (LL)
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8. Adjustment of Device (LL)
Cup drops freely when crank is turned?
Measure cup drop
1.00 cm
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9. Test Procedures (LL) Grind 100-200 grams of dried soil Sieve soil
Mix in distilled water
Place soil on device
Make groove in soil (Figure 3)
Record number of drops
Scrape soil
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10. Figure 3: Liquid Limit Test
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11. Flow Curve (LL) Logarithm of the number of drops and water content
Straight line
Select point with 25 drops= LL
Figure 4
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12. Figure 4: Flow Curve (LL)
Log of number of drops
LL Water Content
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13. Plastic Limit Test (Apparatus)
Hard flat surface
Porcelain mixing dish
Distilled water
Number 40 sieve
1/8 inch welding rod
Balance
Drying oven
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14. Test Procedure (PL) Grind 30-50 grams Sieve soil Mix distilled water
Roll 10 grams out into a coil
Cut into 6-8 pieces
Knead soil
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15. Calculation (PL)
Average Water content from 3 trials.
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16. Non-Plastic When LL or PL tests cannot be performed Non-Plastic (NP)
PL=negative NP
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17. Figure 5: Data Sheet
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