2512
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
4
-200 0 200 400 600 800 1000 1200 1400 1600
0,0
0,2
0,4
0,6
0,8
1,0
U U
carillo
(400 kPa)
time (min)
Degree of consolidation
(a)
(b)
figure 4. Variation of global degree of consolidation
for applied loads (100, 200, 400 and 800 kpa), it is
noted that the degree of consolidation as predicted by
the Carillo’s theory
reaches 100% for a time less than 24
hours, while the degree of consolidation U, estimated
from equation (11) by using measurements of serie 3
results, reaches 100% in 24 hours.
one can also remarks
that by using the Carillo’s theory
a
lower degree of consolidation which starts from 10% is
obtained, however when using measurements of in series
3 simple approximate methods, higher degrees of
consolidation starting from 70% are obtained.
comparing between recorded and predicted global
degree of consolidation U, it follows that the evolution
of U predicted by the
Carrillo’s theory are overestimated
with respect to that deduced from recorded settlement
from series 3. the final global consolidation degree U is
identical by using the two methods.
conclUsion
this paper presented an experimental study conducted
on tunis soft clay, in which three types of oedometer
tests were executed: a standard oedometer test; an
oedometer test on specimen soil improved by an element
of geodrain and test a similar test to the second one by
preventing the vertical drainage. from measurements
coefficients of permeability k
v
and k
r
were determined
by the variable head permeability test. in addition,
coefficients of vertical and radial consolidation c
v
and
c
r
were determined from the evolution in time of
settlement at different levels of consolidation stress.
comparison between the ratios k
r/
k
v
and c
r/
c
v
demonstrated that equality between the two ratios only
happens at high level of stress consolidation, contrarily
to the common assumption made in previous studies.
predictions of the global degree of consolidation showed
that
the Carillo’s theory
leads to overestimated results
with respect to predictions from recorded settlements.
further, the effect of vertical and radial consolidations
from the observed global consolidation of improved
tunis soft soils was discussed.
Acknowledgement:
authors gratefully appreciate the help provided by mrs.
s. Boussetta during the experimental work carried out at
the soil mechanics laboratory of the national
engineering school of tunis.
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0,0
0,2
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0,6
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1,0
U U
Carillo
(800 kPa)
time (min)
Degree of consolidation
