Geoscience Reference
In-Depth Information
Table 3.13
Engineering properties of peat (http://www.roadex.org/, 2004).
Types of peat
Property
Fibrous
Medium decayed
Amorphous granular
Water content (%)
700-2000
500-1200
500-900
Ash content (%)
1.5-3.0
3-8
8-30
In situ
bulk density (kg m
−
3
)
900-1100
900-1100
900-1100
Dry density (kg m
−
3
)
40-70
70-100
100-140
Void ratio
10-25
8-17
7-13
Permeability (m s
−
1
)
10
−
5
-10
−
6
10
−
6
-10
−
7
10
−
7
-10
−
8
In situ
bulk density
The
in situ
bulk density of a peat bog depends predominantly on its moisture con-
tent. Amorphous granular peats can have
in situ
undrained bulk densities of up to
1,200 kg/m
3
, whilst very woody fibrous peats can have
in situ
densities as low as
900 kg/m
3
in unsaturated conditions.
Specific gravity
The specific gravity of peat typically varies from 1.4 to 1.8, with the higher ranges
again reflecting a higher mineral content.
Void ratio
The initial void ratio of peat varies with the type of peat and moisture content, ranging
from 7 to 25.
Permeability
The permeability of peat in the field can be highly variable depending on its morphology
and can reduce dramatically when subjected to loading. The permeability of virgin peat,
for example, can range from 10
−
2
to 10
−
5
cm s
−
1
, but when loaded, such as with a
low road embankment, it can quickly reduce to 10
−
6
cm s
−
1
, or to as low as 10
−
8
to
10
−
9
cm s
−
1
under a higher embankment.
Tables 3.12 and 3.13 show some typical engineering properties of peat.
