Environmental Engineering Reference
In-Depth Information
e
e
e
C
C
m
C
t
C
t
u
u
u
a
u
u
w
a
a
w
(a)
(b)
w
e
w
G
w
s
D
G
C
t
D
m
s
t
G
D
m
s
D
t
u
u
w
u
a
u
a
u
w
a
(c)
(d)
Figure 13.70
Void ratio and water content constitutive relationships for unsaturated soil: (a)
void ratio versus logarithm of stress state relationship; (b) compression of void ratio curves onto
common stress state variable axis; (c) water content versus logarithm of stress state relationship;
(d) compression of water content curves onto common stress state variable axis.
e
vs (
u
a
−
u
w
)
(curve 2)
Increasing initial
degree of
saturation
Increasing initial
degree of
saturation
wG
s
vs (
u
a
u
w
) (curve 4)
−
e
vs (
σ
−
u
a
) (curve 1 and 3)
0.1
1
10
100
1000
10,000
Log (
σ −
u
a
) or (
u
a
−
u
w
)
Figure 13.71
General relationship between curves that define the mass and volume change
behavior of an unsaturated soil.
(i.e.,
u
a
=
0), while the pore-water pressure
u
w
can
be highly negative. The unsaturated soil specimens are
generally placed within a confining metal ring and allowed
to imbibe water until soil suction approaches zero. The soil
specimens are then placed onto a high-air-entry ceramic
disk in the pressure plate apparatus.
Positive matric suctions are applied to a soil specimen
through use of the axis translation technique (Hilf, 1956).
The water pressure is usually maintained at zero and a
positive pore-air pressure is applied. Therefore, the matric
suction in the soil specimen can be varied by applying dif-
ferent air pressures to the specimen.
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