ATTERBERG LIMITATTERBERG LIMIT

By By

M. Firdaus, ST, MTM. Firdaus, ST, MT

www.dauspoli.co.ccwww.dauspoli.co.cc

DefinitionDefinition Where a fine soil contains clay minerals, the soil can knead

(remolded) without causing cracks.

This cohesive properties due to the absorbed water (absorbed water) around the surface of clay particles. When the water level is very large, a mixture of soil and water will become very mushy like a liquid.

One of the characteristics of fine grained cohesive soil is plasticity, namely the ability of soil particles to remain attached to one another so as to define a cohesive soil plasticity, necessary physical position on the soil water content, called the consistency.

Atterberg dividing the physical position on the clay soil water content into 4 conditions:

Liquid LimitLiquid Limit Liquid Limit (LL) is the water content at the boundary Liquid Limit (LL) is the water content at the boundary

between the liquid and plasticbetween the liquid and plastic

In this position, spread and reduced grain moisture In this position, spread and reduced grain moisture content resulting reduction in soil volumecontent resulting reduction in soil volume

To determine the liquid limit laboratory testing using a tool consisting of a brass bowl that rests on the hard rubber. Bowl can be lifted and dropped by an eccentric lever operated with rotator.

Casagrande testing Casagrande testing devices:devices:

GRAFIK BATAS CAIR

50

52

54

56

58

60

10 100

JUMLAH PUKULAN

KA

DA

R A

IR (

%)

LIQUID LIMIT GRAPHLIQUID LIMIT GRAPH

Plastic LimitPlastic Limit Plastic Limit (PL) is the water content at the Plastic Limit (PL) is the water content at the

boundary position between the plastic and semi boundary position between the plastic and semi solidsolid

The difference between LL and PL-called plasticity The difference between LL and PL-called plasticity index, PI (Plasticity Index) which is expressed in index, PI (Plasticity Index) which is expressed in the equation: PI = LL – PLthe equation: PI = LL – PL

If the PI the greater, then the amount of clay If the PI the greater, then the amount of clay particles in the soil more and more. If the PI is low, particles in the soil more and more. If the PI is low, for example in the silt soil, little reduction in water for example in the silt soil, little reduction in water levels would result in soil becomes dry and vice levels would result in soil becomes dry and vice versa if the water content increased slightly, the versa if the water content increased slightly, the soil becomes liquid.soil becomes liquid.

Indeks CairIndeks Cair Liquidity Index (LI) of soil is defined as:Liquidity Index (LI) of soil is defined as:

Liquid index useful for evaluating if the soil on the Liquid index useful for evaluating if the soil on the disturbed conditions (disturbed).disturbed conditions (disturbed).

LI value > 1, if the natural water content (WLI value > 1, if the natural water content (WNN) is ) is greater than liquid limit of soils and when the greater than liquid limit of soils and when the natural water content (Wnatural water content (WNN) < PL, then the negative ) < PL, then the negative LI that where the soil in the solid or semi solid LI that where the soil in the solid or semi solid condition.condition.

PI

PLw

PLLL

PLwLI NN

Batas SusutBatas Susut Shrinkage limit (SL) is defined boundary water content on Shrinkage limit (SL) is defined boundary water content on

the degree of saturation of 100% where for values below it the degree of saturation of 100% where for values below it there will be no change in volume when dried soil continuesthere will be no change in volume when dried soil continues

It should be noted that, the smaller the shrinkage limit, soil It should be noted that, the smaller the shrinkage limit, soil will more easily change the volume and the less water will more easily change the volume and the less water needed to be able to change volumeneeded to be able to change volume

If SL = 5%, then if the field exceeds the value of soil has If SL = 5%, then if the field exceeds the value of soil has resulted in soil will begin to shrinkageresulted in soil will begin to shrinkage

%100)(

2

21

2

21 xm

VV

m

mmSL w

Example problems :Example problems :

Experimental shrinkage limit produces the following data: :

The volume of water saturated soil in a state = 25 cm3

The volume of soil after oven dried = 16 m3

Heavy water-saturated soil at the time = 45 grm

Weight when oven dry soil = 31 grm

Conclusion :

%16%10031

1).1625(

31

3145

%100)(

2

21

2

21

xSL

xm

VV

m

mmSL w

Example Problems :Example Problems :The experimental results from several test limits -

limits the consistency shown in the table:

Determine the liquid limit (LL), plasticity index (PI). Known ground with PL = 20%, water content in the field WN = 38%

Benda Uji 1 2 3 4

Jumlah pukulanNatural soil weight + cawan (gr)Dry soil weight + cawan (gr)Berat cawan (gr)

1228,1524,2015,30

1723,2220,8015,10

2323,2020,8915,20

2823,1820,9015,00

Conclusion :Conclusion :

Examples of sample:

%64,38%10000,1590,20

90,2018,23

%60,40%10020,1589,20

89,2020,23

%46,42%10010,1580,20

80,2022,23

%38,44%10030,1520,24

20,2415,28

xw

xw

xw

xw

The result of calculation of water content (w) and number of strokes drawn on the diagram:

At 25 times the punch obtained 39% water content, so LL = 39%

Plasticity Index (PI) = LL – PL = 39% - 20% = 19%