Geoscience Reference
In-Depth Information
Criteria
Dr = 30%
Dr = 50%
Dr = 70% Dr = 100%
Maximum
liquefaction
factor
0.8
0.8
0.8
0.8
Liquefaction
Foundation
and upstream
embankment
Upstream
embankment
Upstream
embankment
Upstream
embankment
Localization
Maximum shear
strain
>20%
5%
2%
1%
Local shear (1)
-
Track
-
-
Failure
Upstream
and
downstream
embankment
Shear band
strain >5% (2)
-
-
-
Maximum
horizontal
displacement
(m)
1.5
0.4
0.2
0.1
Security
criterion (3)
Failure
No
No
No
Displacement
Maximum
vertical
displacement
(m)
0.65
0.15
0.075
0.025
Security
criterion (4)
Failure
No
No
No
Table 10.6. Results of the parametric study
Figures 10.18 and 10.19 provide a comparison of the behavior indicators for the
four initial states of the embankment. This comparison leads to the following
conclusions.
Liquefaction factors : these increase during the earthquake but start to decrease
before the end of the seismic loading. This is due to the permeability of the gravels,
which is greater than for sands. If the increase in pore pressure during the seismic
loading is the same for the two soils in undrained condition, this is not the case in
situ, where the possible drainage in the gravels reduces the risk of liquefaction. The
presence of slabs prevents the pore pressure dissipation, which induces higher
liquefaction factors in their surroundings. If the slabs can move under the influence
of the pore pressure increase, then the hypothesis of imperviousness retained for the
calculation is probably too conservative.
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