2592
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
would perform in a completely satisfactory way for the highest
cemented mixtures (for 5% and 7% of cement content).
0
1000
2000
3000
4000
5000
6000
1 2 3 4 5 6 7 8 9 10 11 12
E
ur
(MPa)
Test condition
1 2%C;
'
c
=30 kPa
2 2%C;
'
c
=80 kPa
3 2%C;
'
c
=250 kPa
4 4%C;
'
c
=30 kPa
5 4%C;
'
c
=80 kPa
6 4%C;
'
c
=250 kPa
7 5%C;
'
c
=30 kPa
8 5%C;
'
c
=80 kPa
9 5%C;
'
c
=250 kPa
10 7%C;
'
c
=30 kPa
11 7%C;
'
c
=80 kPa
12 7%C;
'
c
=250 kPa
Test condition
n/C
iv
0.21
=36
n/C
iv
0.21
=29
Figure 6. Stiffness modulus obtained in the unload-reload cycles.
5 COMPRESSIBILITY PARAMETERS
One-dimension compression tests in oedometer cells with
constant rate of deformation (CRD) were performed over soil-
cement specimens in the four moulding conditions presented in
Table 1. The preparation of the different mixtures for these tests
followed the same procedure of the other tests, as expressed
briefly in section 2. Due to the size of the mould, the static
compaction was performed in one layer, although the soil was
placed in several stages followed by tapping. For the calculation
of the mean effective stress (p’) in each test the value of the
coefficient of earth pressure at rest (k
0
) was considered equal to
1 due to the high compaction degree that the specimens were
subjected during moulding (>80% of the Modified Proctor test).
Figure 7 shows two of those tests, corresponding to two
different porosity cement ratios, indicating that these
compressibility curves do not seem to converge.
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.001 0.010 0.100 1.000 10.000 100.000
e
p' (MPa)
n/C
iv
0.21
= 29
n/C
iv
0.21
= 36
Figure 7.Void ratio against mean effective stress for two different
porosity/cement ratios
However, plotting the tests performed over specimens with
the same porosity cement ratio, a unique compressibility line
was obtained. The same has happened for the other two tests
with the other porosity cement ratio of 36. On the contrary,
when specimens with the same cement content but different
void ratio were represented no unique line was obtained. These
results indicate that this ratio can better reproduce the behaviour
in one-dimensional compression than the cement content or
initial void ratio alone.
6 CONCLUSIONS
This paper presented a great number of data from different tests.
Together, they allowed a better understanding of the artificially
cemented soil used in this work. Compressive and tensile
strength, strength envelopes, stiffness parameters and one
–
dimensional behaviour were some of the most important issues
studied. The adjusted porosity/cement ratio revealed to be very
consistent and useful for the analysis of the unconfined
compression strength since a unique trend was obtained
between this variable and n/C
iv
0.21
. A similar trend was obtained
for the indirect tensile strength performing tests over specimens
moulded in the same conditions. The comparison of the two
curves provided a relationship between indirect and
compressive strength of about 11%.
The strength envelope values of the cemented specimens
tested in triaxial compression were obtained through a
procedure based on the Mohr’s circles analysis to s
olve the lack
of representativeness of principal stress analysis due to non
correspondence of the real localised shear locus. In fact, strain
localisation is unavoidable in these very stiff materials, and
consequently, the global stress-strain measurements are no
longer representative of the conditions throughout the shearing
process. Two peak strength envelopes were obtained for each
n/C
iv
0.21
(n/C
iv
0.21
=36:
’=30º and c’=
253 kPa; n/C
iv
0.21
=29:
’=39º and c’= 589
kPa), showing once again the convenience
of this ratio for the analysis of these mixtures behaviour.
This ratio also seems to be very useful to reproduce the one
dimensional compression behaviour of the mixture, since for
each n/C
iv
0.21
a single line was obtained for higher stresses.
7 ACKNOWLEDGEMENTS
This research was developed under the activities of FCT
(Portuguese Foundation for Science and Technology) research
unit CEC, in FEUP [PTDC/ECM/ 099475/2008], and financed
by the European Community (QREN/UE/FEDER), Operational
Program for Competitive Factors "COMPETE".
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