1. Atterberg's Limits Faculty of Applied Engineering and Urban Planning
Civil Engineering Department
Soil Mechanics
ECGD3303
Atterberg's Limits
Lecture 4
Week 2
1st Quadester 2007/2008
UP Copyrights 2007

2. Content Soil Consistency Atterberg Limits Plasticity Index
Liquid Limit
Plastic Limit
Shrinkage Limit
Plasticity Index
Liquidity Index
Plasticity Chart

3. Soil Properties Engineering Properties Index properties
Shear strength – stability of slopes, B.C of soil & earth pressure on retaining wall
Permeability - seepage through earth masses
Compressibility - settlement
Index properties
The properties of soils which are not of primary interest to the geotechnical engineer but which are indicative of the engineering properties are called index properties
Soil classification

5. Soil Consistency
Soil consistence provides a means of describing the degree and kind of cohesion and adhesion between the soil particles as related to the resistance of the soil to deform or rupture
Soil Behave Like:
SOILD at very low moisture content
LIQUID at very high moisture content

6. - + Soil Consistency - Atterberg Limits
Depending on Moisture Content soil can be divided into:
Solid
Semi-Solid
Plastic
Liquid -
Shrinkage Limit (SL)
LI = 0
Moisture Content (w)
Plastic Limit (PL)
Liquidity
Index (LI)
Plasticity Index
(PI) = PL - LL
Liquid Limit (LL)
LI = 1 +

7. Questions?!
20:00 min

8. Liquid Limit - Definition
Liquid Limit (LL) is defined as the moisture content at which soil begins to behave as a liquid material and begins to flow
(Liquid limit of a fine-grained soil gives the moisture content at which the shear strength of the soil is approximately 2.5kN/m2)

9. Liquid Limit - Measurement
First Method
Casagrande
Apparatus
ASTM D-4318

10. Liquid Limit - Measurement
Liquid Limit (LL) at N = 25

11. Liquid Limit – Flow Index

12. Liquid Limit - Measurement
Second Method
Fall Cone Method BS1377

13. Liquid Limit - Measurement
Liquid Limit (LL) at d = 20 mm

14. Questions?!
45:00 min

15. Plastic Limit - Definition
The moisture content (%) at which the soil when rolled into threads of 3.2mm (1/8 in) in diameter, will crumble.

16. Plastic Limit - Measurement
First Method
ASTM D-4318
PL = w% at d 3.2 mm (1/8 in.)

17. Plastic Limit - Measurement
Second Method
Fall Cone
Method BS1377
Plastic Limit (PL) at d = 20 mm

18. Questions?!
75:00 min

19. Plasticity Index - Definition
Plasticity Index is the difference between the liquid limit and plastic limit of a soil.
PI = LL – PL

20. Question!! Plasticity Index - Definition PI (%) = 4.12 IF (%)
PI (%) = 0.74 IFC (%)
Question!!
Which PI is more reasonable for construction projects? The high one or the low one?!

21. Questions?!
90:00 min

22. Shrinkage Limit - Definition
The moisture content, in percent, at which the volume of the soil mass ceases to change

23. Shrinkage Limit - Definition

24. Shrinkage Limit - Measurement

25. Questions?!
90:00 min

26. - + Soil Consistency - Atterberg Limits
Depending on Moisture Content soil can be divided into:
Solid
Semi-Solid
Plastic
Liquid -
Shrinkage Limit (SL)
LI = 0
Moisture Content (w)
Plastic Limit (PL)
Liquidity
Index (LI)
Plasticity Index
(PI) = PL - LL
Liquid Limit (LL)
LI = 1 +

27. Liquidity Index - Definition

28. Plasticity Chart - Definition
Casagrande (1932) studied the relationship of the plasticity index to the liquid limit of a wide variety of natural soils.
He proposed a plasticity chart

29. Organic
Inorganic
Silt
Clay

30. Questions?!
120:00 min