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Consistency of Soil

The document discusses different soil consistency concepts including Atterberg limits, which classify soils based on moisture content into solid, semi-solid, plastic, and liquid states. It also examines methods for determining the liquid limit, plastic limit, and shrinkage limit of soils in order to calculate values like plasticity index and liqudity index. A plasticity chart graphs the relationship between liquid limit and plasticity index for different soil types.

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662 views29 pages

Consistency of Soil

The document discusses different soil consistency concepts including Atterberg limits, which classify soils based on moisture content into solid, semi-solid, plastic, and liquid states. It also examines methods for determining the liquid limit, plastic limit, and shrinkage limit of soils in order to calculate values like plasticity index and liqudity index. A plasticity chart graphs the relationship between liquid limit and plasticity index for different soil types.

Uploaded by

JQ
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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COLLEGE OF ENGINEERING

Civil Engineering Department

Soil Mechanics
NCE 412

Atterberg's
Limits

Lecture 4
Week 2
Content

• Soil Consistency
• Atterberg Limits
• Liquid Limit
• Plastic Limit
• Shrinkage Limit

• Plasticity Index
• Liquidity Index
• Plasticity Chart
Soil Consistency

Soil consistency 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:


SOLID at very low moisture content
LIQUID at very high moisture content
Soil Consistency - Atterberg Limits

Depending on Moisture Content soil can be


divided into:

- 1. Solid
Moisture Content (w)

Shrinkage Limit (SL)

2. Semi-Solid
LI = 0
Plastic Limit (PL)
Liquidity Plasticity Index
3. Plastic
Index (LI) (PI) = PL - LL
Liquid Limit (LL)
LI = 1
+ 4. Liquid
Questions?!

20:00 min
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)
Liquid Limit - Measurement

First Method

Casagrande
Apparatus

ASTM D-4318
Liquid Limit - Measurement

Liquid Limit (LL) at N = 25


Liquid Limit – Flow Index

w1=44

w2=39

Group Work
Calculate Flow Index
N1=20 N2=30

Flow Index
Liquid Limit - Measurement

Second Method

Fall Cone Method BS1377


Liquid Limit - Measurement

Liquid Limit (LL) at d = 20 mm


Questions?!

45:00 min
Plastic Limit - Definition

The moisture content (%) at which the soil


when rolled into threads of 3.2mm (1/8 in) in
diameter, will crumble.
Plastic Limit - Measurement

First Method

ASTM D-4318

PL = w% at d 3.2 mm (1/8 in.)


Plastic Limit - Measurement

Second Method

Fall Cone
Method BS1377

Plastic Limit (PL) at d = 20 mm


Questions?!

75:00 min
Plasticity Index - Definition

Plasticity Index is the difference between


the liquid limit and plastic limit of a soil.

PI = LL – PL
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?!
Questions?!

90:00 min
Shrinkage Limit - Definition

The moisture content, in percent, at which the


volume of the soil mass ceases to change
Shrinkage Limit - Definition
Shrinkage Limit - Measurement
Questions?!

90:00 min
Soil Consistency - Atterberg Limits

Depending on Moisture Content soil can be


divided into:

- 1. Solid
Moisture Content (w)

Shrinkage Limit (SL)

2. Semi-Solid
LI = 0
Plastic Limit (PL)
Liquidity Plasticity Index
3. Plastic
Index (LI) (PI) = PL - LL
Liquid Limit (LL)
LI = 1
+ 4. Liquid
Liquidity Index - Definition
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


Organic
Inorganic

Silt
Clay
Questions?!

120:00 min

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