Geoscience Reference
In-Depth Information
120
100
80
60
40
20
0
0
50
100
150
200
Temperature (˚C)
250
300
350
400
450
Figure 3.7
Duration versus drying temperature (
◦
C) (
after
Zainorabidin and Bakar, 2003).
3.9 WATER CONTENT
Water content (also commonly referred to as natural moisture content) is one of the
most common soil parameters, expressed in term of mass or weight.
w
=
w
w
/w
s
×
100%
(3.3)
where
w
=
water content
w
w
=
weight of water
w
s
weight of dry soil
A small value of
w
indicates dry soil, while a large value indicates a wet one.
The water content can easily measured in the laboratory by conducting a moisture
content test (ASTM D2216 or BS 1377: 1990), which involves drying a soil sample in
an oven at 105
◦
C for 24 hours.
For peat soils, there is a general fear that standard drying of the soil at 105
◦
C during
24 hours will lead to charring of the organic component in peat, thus producing too
large a figure for water content. Some therefore advocate a lower temperature, between
50 and 95
◦
C. Skempton and Petley (1970) and Kabai and Farkas (1988) investigated
the effect, and concluded that the loss of organic matter at 105
◦
C is insignificant,
while drying at lower temperatures retains a small amount of free water. Zainorabidin
and Bakar (2003) investigated the drying temperature effect for hemic peat soil and
suggested that for temperatures between 100 and 200
◦
C the drying duration required
is between 24 and 60 hours (Figure 3.7).
Standard practice is to dry at a temperature of 105
◦
C. After a 24 hour drying
period, the water content is then calculated using the formula
=
w
2
−
w
3
w
=
w
1
×
100%
(3.4)
−
w
3
where
w
1
=
weight (or mass) of container
+
lid
w
2
=
weight (or mass) of container
+
lid
+
wet soil
w
3
=
weight (or mass) of container
+
lid
+
dry soil
