Geoscience Reference
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302
Multiscale Geomechanics
(a)
(b)
(c)
Figure 9.23.
Directional variations of: (a)
d
2
W
; (b)
det(C
e
s
)
; and (c)
det(C
ep
)
for Hostun sand at
D
r
=40
with
σ
3
= 100 kPa
and
ξ =
σ
1
σ
3
=2.5
under axisymmetrical conditions
In Figure 9.24, we present the deformed mesh and the displacement increments
at the last acceptable stage of excavation (the balance of forces is verified). On the
same figure, the potential directions satisfying the condition of Rice are indicated by
lines with these directions. If we compare the two diagrams, we see that the failure
mechanisms obtained by the two models are different. When the Mohr-Coulomb
criterion is used, we are in the presence of an unrealistic swelling of the medium
because of the elastic behavior during the excavation and the unloading of the soil.
Thanks to its reduced elastic range, no swelling occurs with the Hujeux model, leading
to results closer to observations [BEL 98]. The difference in the geometry of the failure
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