Geoscience Reference
In-Depth Information
Figure 3.26
Correlation of specific gravity with loss on ignition for Irish peat (
after
O'Loughlin and
Lehane, 2003).
den Haan (1997) simplified the above equation as follows.
1
G
s
=
N
1
.
365
+
(1
N
)
2
.
695
−
(3.16)
Figure 3.26 shows the plot of specific gravity versus loss on ignition of Irish peat.
Figure 3.27 shows a similar plot for Dutch peat.
The values of specific gravity obtained from equation (3.17) are somewhat lower
than given by Skempton and Petley (1970).
In general, the high lignin content of tropical peat gives it a slightly lower specific
gravity compared with that of temperate peat, with
G
s
in the range 1.07-1.70, and an
average of about 1.40.
3.13.6 Bulk density vs. loss of ignition
Figure 3.28 shows a graph of bulk densities and ignition loss for peat soils. The bulk
densities of peat are in the range 0.8-1.2Mg/m
3
compared with bulk densities of
mineral soils, which are in the range 1.80-2.00Mg/m
3
. This is due to the lower spe-
cific gravity of solids found and higher water-holding capacity in peat compared with
inorganic soils.
Based on extensive tests performed on Dutch peat, den Haan and El Amir (1994)
proposed the following empirical relationship:
γ
sat
(
kN/m
3
)
=
12
.
266
−
3
.
156
OC
(3.17)
