Geoscience Reference
In-Depth Information
Fig. 8.3
Sketch of a thought experiment on a
soil sample SS, supported on a porous
plate PP in a receptacle C. The
average pressure in the water in the
sample is equal to ( ρ w gd ). The
blow-up section B-U is shown in
Figure 8.4.
SS
PP
B-U
C
d
FT
FT
Fig. 8.4
Blow-up view of the porous plate (or membrane) supporting the porous material,
as shown in Figure 8.3. The volume occupied by water is shown as dark area.
to the atmospheric pressure; this negative pressure is often also called soil water suction
or soil water tension. In the remainder of this chapter the soil water suction, whenever
expressed as a positive height of water column, will also be denoted by H (
=− ψ w ).
Typically, the relationship between the soil water pressure and the water content is
of the form shown in Figure 8.5. This relationship is also variously referred to as the
soil water characteristic , the soil water suction relationship and the soil water reten-
tion relationship . Some other examples of soil water characteristic curves are shown in
Figure 8.6.
Equilibrium moisture content profile in a homogeneous soil
If the variable z
H ) refers to the height above the water table, the
soil water characteristic also provides a description of the water content distribution in a
homogeneous soil profile, which occurs under hydrostatic conditions, that is when there
is no flow. This is illustrated in Figure 8.7. As defined in Chapter 1, the water table is
=
d (
=−
p w w =
Search WWH ::




Custom Search