Geoscience Reference
In-Depth Information
Engineering properties of peat and
organic soils
3.1 INTRODUCTION
As mentioned in Chapter 2, degree of humification, surface charge characteristics,
resistivity and other index parameters, such as water content, liquid limits, specific
gravity, unit weights, zeta potential and pH, are also useful parameters for peat and
organic soils. We will look at how these parameters are useful for describing peat soil,
how they are assessed and measured, and their relation with each other, as well as with
other engineering parameters such as void ratios, deformation parameters and shear
strength that are dealt with in later chapters.
3.2 PHASES OF PEAT
In conventional soil mechanics, soils are considered as particulate materials, as opposed
to rocks, and can simultaneously contain three phases: solid, liquid and gas (Fig-
ure 3.1). The liquid and gas phases are contained in the voids or pores between the
solid particles. From these phases, the weight-volume relationships of soils are derived.
These are the moisture content, degree of saturation, unit weight, density, void ratio
and specific gravity of soils.
For the case of peat and organic soil, the solid phase consists of two com-
ponents: organic matter and inorganic earth minerals. The relative proportion of
Weight
Volume
Volume
Mass
W
a
0
V
a
0
V
a
Air
M
a
Air
V
v
V
v
W
w
Water
V
w
V
Water
V
w
V
W
M
w
M
V
s
V
s
W
s
Solids
M
s
Solids
Figure 3.1
Soil phase diagram.
