Nature and Phase Properties of Unsaturated Soil - Unsaturated Soil Mechanics in Engineering Practice - page 69

a soil. Saturated and completely dry conditions are special
limiting cases of a wide range of possible soil conditions.

The total and dry densities of the overall soil mass can
also be expressed in terms of other volume-mass properties
of the soil (e.g., S , e , w , and G s ). Assuming that the mass
of the air phase, M a , is negligible, the total mass of the soil
is the sum of the mass of the water, M w , and the mass of
the soil solids, M s . The total volume of the soil, V , is given
by the volume of the soil solids, V s , and the volume of the
voids, V v . The density of a soil, ρ , can be rewritten in the
following forms:

2.4.6.1 Soil Density
Two commonly used soil density definitions are total density
and dry density. The total density of a soil, ρ , is the ratio
of the total mass M to the total volume of the soil, V :

M
V

ρ = (2.64)

M s + M w

ρ = (2.66)

The total density is also called the bulk or moist density.
The dry density of a soil, ρ d , is defined as the ratio of the mass
of the soil solids, M s , to the total volume of the soil, V :

V s + V v

G s ρ w V s + wG s ρ w V s

ρ = (2.67)

V s + eV s

M s
V

G s ( 1 + w )

ρ d = (2.65)

ρ = ρ w (2.68)

1 + e

Typical minimum and maximum dry densities for various
soils are presented in Table 2.16. Other soil density defini-
tions are the saturated density and the buoyant density. The
saturated density of a soil is equal to the total density of the
soil for the case where the voids are filled with water (i.e.,
V a =

Substituting the basic volume-mass relationship (i.e.,

Se wG s ) into Eq. 2.68 gives the following equation for

the total density:

=

G s + Se

ρ = ρ w (2.69)

1 + e

0 and S = 100%).

Figure 2.46 Relationship between volume-mass properties of unsaturated soil.