Environmental Engineering Reference
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but illustrate several important characteristics of unsaturated
soil behavior (e.g., swelling and collapsible behavior).
Four series of stress paths were used to illustrate the
volume-mass constitutive surfaces for the unsaturated soil
shown in Fig. 13.50. For stress path 1, the soil starts as a
slurry, is loaded to a specified net mean stress, and then dried
under constant net mean stress to a soil suction of 10
6
kPa.
For stress path 2, the soil starts as a slurry and is then dried
to a designated suction value and loaded under constant-
soil-suction conditions to a net mean stress of 10
4
kPa. For
stress path 3, the soil is initially dried from slurry condi-
tions, loaded to a specified net mean stress and then wetted
under a constant net mean stresses to a suction of 10
6
kPa.
For stress path 4, the soil is initially dried from slurry con-
ditions, wetted to a specified suction, and then loaded under
a constant suction to a net mean stress of 10
4
kPa.
The series 1 and 2 stress paths are used to study the
volume-mass behavior associated with soil specimens when
starting from the same initial slurry condition and ending at
the same final stress state. However, a different stress path is
followed during each of the the drying processes. Similarly,
stress path series 3 and 4 are used to study the volume-mass
10
6
100
0.1
0.1
200
p
Net mean stress (kPa)
Figure 13.46
Stress path followed for artificial silt (from Pham,
2002).
13.6.8.3 Prediction Results for Volume-Mass
Constitutive Surfaces
Several series of stress paths can be selected to illustrate
the form of the entire volume-mass constitutive surfaces for
artificial soils. The selected stress paths are relatively simple
1.4
Initial condition
1.2
1.0
0.8
0.6
0.4
0.2
0.0
10
6
0.1
1
10
100
1000
10,000
100,000
Soil suction, kPa
Figure 13.47
Void ratio changes for artificial silt.
50
Initial condition
45
40
35
30
25
20
15
10
5
0
10
6
0.1
1
10
100
1000
10,000
100,000
Soil suction, kPa
Figure 13.48
Gravimetric water content changes for artificial silt.
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