ATTERBERG LIMITS

 The presence of water in fine-grained soils can significantly
affect associated engineering behavior, so we need a
reference index to clarify the effects. (The reason will be

discussed later in the topic of clay minerals)

In percentage

(Holtz and Kovacs, 1981)

Fluid soil-waterIncreasing water content Liquid State Liquid Limit, LL
mixture Plastic State Plastic Limit, PL
Semisolid State Shrinkage Limit, SL
Dry Soil Solid State

Casagrande Method Cone Penetrometer
Method
(ASTM D4318-95a)
(BS 1377: Part 2: 1990:4.3)
Professor Casagrande
standardized the test and This method is developed by
developed the liquid limit the Transport and Road
device. Research Laboratory, UK.

Multipoint test Multipoint test

One-point test One-point test

Dynamic shear test Particle sizes and water

 Shear strength is about 1.7 Passing No.40 Sieve (0.425
~2.0 kPa. mm).

 Pore water suction is about Using deionized water.
6.0 kPa.
The type and amount of
(review by Head, 1992; Mitchell, 1993). cations can significantly
affect the measured results.

•Device

N=25 blows

Closing distance =
12.7mm (0.5 in)

(Holtz and Kovacs, 1981) The water content, in percentage, required to close a
distance of 0.5 in (12.7mm) along the bottom of the
groove after 25 blows is defined as the liquid limit

•Multipoint Method

w

N Das, 1998

Flow index, IF = w1 − w2 (choose a positive value)

log(N2 / N1 )

w = −IF log N + cont.

•One-point Method  N  t an
 25 
• Assume a constant slope of the LL = wn
flow curve.
N = number of blows
• The slope is a statistical result of
767 liquid limit tests. wn = corresponding moisture content
tan  = 0.121

Limitations:

• The  is an empirical coefficient,
so it is not always 0.121.

• Good results can be obtained only
for the blow number around 20 to
30.

•Device

This method is developed
by the Transport and Road
Research Laboratory.

(Head, 1992)

Penetration of cone•Multipoint Method
(mm) 20 mm

LL
Water content w%

(Holtz and Kovacs, 1981)

The plastic limit PL is defined as the water content at which
a soil thread with 3.2 mm diameter just crumbles.
ASTM D4318-95a, BS1377: Part 2:1990:5.3

Definition of shrinkage
limit:
The water content at
which the soil volume
ceases to change is
defined as the shrinkage

SL limit.

(Das, 1998)

Soil volume: Vi
Soil mass: M1

Soil volume: Vf
Soil mass: M2

(Das, 1998)

SL = wi (%) − w(%)

=  M1 − M2 (100) −  Vi − Vf (w )(100)
M2 M2

 “Although the shrinkage limit was a popular classification test
during the 1920s, it is subject to considerable uncertainty
and thus is no longer commonly conducted.”

 “One of the biggest problems with the shrinkage limit test is
that the amount of shrinkage depends not only on the grain
size but also on the initial fabric of the soil. The standard
procedure is to start with the water content near the liquid
limit. However, especially with sandy and silty clays, this
often results in a shrinkage limit greater than the plastic limit,
which is meaningless. Casagrande suggests that the initial
water content be slightly greater than the PL, if possible, but
admittedly it is difficult to avoid entrapping air bubbles.”
(from Holtz and Kovacs, 1981)

(Mitchell, 1993)

Plasticity index PI Liquidity index LI
For describing the For scaling the natural
range of water content water content of a soil
over which a soil was sample to the Limits.
plastic
PI = LL – PL LI = w − PL = w − PL
PI LL − PL
Liquid State C
w isthe water content
Liquid Limit, LL
LI <0 (A), brittle fracture if sheared
PI Plastic State B 0<LI<1 (B), plastic solid if sheared
Plastic Limit, PL LI >1 (C), viscous liquid if sheared

Semisolid State A

Shrinkage Limit, SL

Solid State





PLASTIC LIMIT (PL)

Can Number 1 2
19.6
Mass of can + Wet Soil (g) 20.7 17.8
8.4
Mass of can + Dried Soil (g) 18.7

Mass of empty can (g) 8.1

Moisture Content (%)

Average Moisture Content (%)

Di atas adalah data dari ujikaji
Casagrande yang dijalankan di
makmal. Kirakan Indek Plastik
bagi tanah tersebut.