Geoscience Reference
In-Depth Information
7.4.2.1.
Saint-Herblain clay
Saint-Herblain clay is a clayey river alluvial deposit from the Loire Valley's
Paleolithic period. It is slightly or moderately organic and characterized by a high
plasticity index (
I
p
=
42) with plastic limit
wp
= 48% and liquid limit
wl
= 102%. Its
compression index is equal to 0.96. The samples were taken from a depth of 5.5 to
7.5 m. They correspond to a very soft clay with an
in situ
void ratio of between 2.25
and 2.6, and a mean undrained shear strength
c
u
equal to 26 kPa. The mean cluster
size
d
was taken to be equal to 0.001 mm, the initial stiffness
k
n0
= 60 N/mm
2
,
k
t0
/k
n0
= 0.3. The other parameters were determined either directly from
experimental curves or are presented in Table 7.3.
e
ref
p
ref
(MPa)
λ
φ
μ
（
˚
）
φ
0
（
˚
）
c
c
β
k
p0
/k
n0
2.60
0.01
0.96
31.00
31.00
0. 20
1.00
0.50
Table 7.3.
Model parameters for Saint-Herblain clay
Results of tests reported by Zentar [ZEN 99] were used here for the evaluation of
the model. Four
K
consolidation tests were performed with
K
= 0.9, 0.92, 0.77 and
0.51 (
K
= σ
'
3
/
σ
'
1
). They were consolidated to different points in the
p'
−
q
plane, as
shown in Figure 7.13. The samples were then sheared in an undrained condition up
to failure.
q (MPa)
q (MPa)
0.20
0.20
EX
P
M
O
DEL
EXP
MODEL
M=1.25
0.16
0.16
0.12
0.12
0.08
0.08
0.04
0.04
0.00
0.00
-2
0
2
4
6
8
0.00
0.04
0.08
0.12
0.16
0.20
ε
1
(%)
p' (MPa)
(a) stress-strain relationship
(b) evolution of void ratio
Figure 7.13.
Experimental results and numerical simulations of undrained triaxial tests
on anisotropically consolidated Saint-Herblain clay
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