1154
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
3.2 Filter paper testing results
Figure 7(a) shows the variation of the gravimetric water content
with suction. There is an apparent higher overall water retention
capacity of the treated soil due to the higher initial water content
however it can be seen that the rate of water loss with suction of
the lime treated soils is not much different compared to the
respective untreated sample, despite the fact that lime has
changed the soil structure. Despite the expected change in the
nature of the soil (mineralogy and size /specific surface) after
treatment, at higher suctions where adsorptive phenomena
predominate, the differences between treated and untreated soil
are not clear, which is difficult to explain. For the untreated soil
it is expected that compaction conditions do not affect the
results so much, as at low saturation adsorptive forces gradually
predominate and the effect of soil structure appears to have little
influence on the SWRC. However it would be expected that the
water retention of the chemically treated soils should have been
different to that of the untreated soil, due to the change in the
composition and specific surface area of the soil (related to the
adsorptive forces) brought about by the lime treatment. This is
not noticeable in the results of treated sample compacted dry of
optimum; there is however some indication that this happens to
some extent for the lime-treated soils compacted at higher water
content (these show a slightly steaper desorption slope,
implying faster desaturation) which could perhaps be attributed
to the fact that water facilitated further pozzolanic reactions due
to enhanced ion migration, and hence further alteration of the
microstructure. As for untreated soils, the lime-treated sample
compacted dry of optimum, showed a lower water retention
capacity compared to the respective sample compacted dry of
optimum due to the more open structure. As with untreated
soils, the deformability of the lime-treated samples compacted
wet of optimum is higher (see Fig 7c), however the lime treated
samples showed overall much lower volumetric strains with
respect to the untreated soil, especially for the higher lime
content as a result of cementation. Overall it can be clearly
noted that cementation considerably affected the strain related
quantities (the void ratio and the volumetric strain) due to the
increased stiffness.
(a)
(b)
4 CONCLUSIONS
A number of triaxial tests and filter paper tests were carried out
to assess the effect of lime on the hydromechanical properties of
statically compacted London Clay and lime-treated London
Clay samples respectively. The results showed that the lime-
treated soil became increasingly stiffer, stronger but also more
brittle with the increase in lime percentage and also when it was
air-cured as opposed to water-cured. The strain softening and
stiffness degradation at narrow strain ranges was even more
pronounced for partially unsaturated air-cured lime-treated
London Clay soil was due to the combined effect of lime and
suction. It appears that water curing and lower percentages of
lime could in fact be more beneficial as they increase
sufficiently the stiffness and strength of the soil without
resulting in very brittle behaviour and abrupt strain softening
within the range of strains of relevance for engineering design.
The effect of the lime on the water retention capacity of the
material was found to be less pronounced but a considerable
reduction in volumetric changes with suction change was noted.
(c)
Figure 7. Filter paper results plotted vs matric suction: (a) gravimetric
water content; (b) void ratio; (c) volumetric strain
5 ACKNOWLEDGEMENTS
Most part of the research was funded from grant EP/E037305/1
of the UK Engineering and Science Research Council grant.
Some SWRC data was obtained by Luke Katchoff.
6 REFERENCES
Chandler R.J. and Gutierrez C.I. 1986. The filter paper method for
suction measurement.
Géotechnique
6(2), 265-168
King C. 1981. The stratigraphy of the London Clay and associated
deposits. Tertiary
Research Special Paper 6
, Backhuys, Rotterdam.
Vaughan P.R. 1993. Engineering behaviour of soft rocks. Some answers
and some questions. In Anagnostopoulos, Schlosser, Kalteziotis and
Frank (eds),
Geotechnical Engineering of Hard Soils-Soft Rocks
.
Balkema, Rotterdam, 1741-1766
