Geoscience Reference
In-Depth Information
1.5
12
1
8
1
0.8
1.0
0.75
4
0.5
D
r
= 0.05
0
0.35
0.2
0.5
-4
D
r
= 0.05
-8
0.0
0
5
10
15
20
25
30
0
5
10
15
20
25
30
ε
1
(%)
ε
1
(%)
Figure 7.7.
Numerical simulations for various initial relative densities
7.3.2.
Undrained triaxial tests
Undrained triaxial tests have also been simulated, under the same set of
parameters. The experimental results are plotted in Figure 7.8 and are compared
with the predicted results in Figure 7.9. We can see that for strongly contractive
materials, i.e. small values of the relative density, a maximum strength is obtained in
the
q
− ε
1
plane followed by a decrease in the deviatoric stress down to a minimum
strength that is almost zero for a relative density close to zero. This represents the
phenomenon called static liquefaction. For slightly higher relative densities, the
same pattern is first observed, but it is then followed by an increase in the deviatoric
stress up to the ultimate strength at large deformations, corresponding to the critical
state. For dilative materials, the deviatoric stress increases monotonically up to an
ultimate stress achieved at large deformations when the critical state is reached.
0.8
0.8
D
r
= 0.58
0.6
0.6
0.52
0.52
0.4
0.4
0.47
D
r
= 0.58
0.47
0.37
0.2
0.2
0.17
0.37
0.17
0.12
0.6
0.12
0.6
0.0
0.0
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0
5
10
15
20
25
ε
1
(%)
(
σ
1
+
σ
2
+
σ
3
) / 3 (
MPa)
(a)
(b)
Figure 7.8.
Undrained triaxial tests on Hostun sand for various initial relative densities:
(a) stress-strain relation; and (b) effective stress path
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