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Technical Committee 307 /
Comité technique 307
organic loss on the shear strength by modeling the leaching as a
diffusion process and the organic loss as an exponential decay
process. The study shows that DWS can be used in geotechnical
applications.
Figure 9. Friction angle of drinking water sludge as a function of
decomposition rate of organic matter (Figure 7 of Watanabe and
Komini).
Di Emidio et al. investigated the possibility of reusing
dredged materials in landfill cover as a low-cost alternative.
Enormous amounts of dredged material are generated from
maintenance, construction, and remedial works related to water
systems, and these materials are usually disposed of in landfills.
Therefore, the reuse of dredged materials is important all over
the world. For use in landfill cover, the dredged material must
have low hydraulic conductivity and must retain the
contaminants already present in it. In their study, Di Emidio et
al. used dredged sediment obtained from Kluizendok in Ghent,
Belgium and commercially processed kaolin Rotoclay® HB
clay, and treated both with an anionic polymer Sodium
CarboxyMethylCellulose (Na-CMC). Polymerization is
particularly useful for dredged materials contaminated with
metallic wastes. The authors investigated the mechanisms
through which polymers can improve the efficiency of dredged
sediments in waste containment impermeable barriers. Di
Emidio et al. also conducted hydraulic conductivity and batch
sorption tests to study the barrier performance and transport
parameters of the treated dredged material and clay. The results
showed that polymer treatment maintained low hydraulic
conductivity of soil in electrolyte solutions and helped the
material contain the spread of pollution. The results indicated
that dredged sediments can be reused as alternative low-cost
impermeable landfill cover.
Nakano and Sakai performed consolidation and triaxial tests
on cement treated dredged soil samples collected from Nagoya
Bay, Japan and modeled their elemental behavior using the SYS
Cam-clay model. About 1.3 million m
3
of dredged soil is
produced annually in Nagoya Bay, which has limited storage
capacity because of which there is a pressing need for using the
dredged soil as a geo-material. However, the clayey soil has low
shear strength and high water content because of which cement
is used as a stabilizer to improve its mechanical properties. The
constitutive model of Nakano and Sakai reproduced the
elemental test results reasonably well and the authors also
performed finite element analysis using the software
GEOASIA
in order to capture the nonuniform deformation of triaxial test
samples.
Air-foam treated lightweight soil, known as Super Geo-
Material (SGM), is an example of an alternate material that is
useful in harbor and airport constructions because of its light
weight, safety features, and recyclability. Kataoka et al. mixed
six different types of soils from Japan with seawater, blast
furnace cement, and animal-protein hydrolyzed air-foam to
prepare SGM specimens. They measured the unconfined
compressive strength and small-strain shear modulus of the
specimens, and studied their microstructure using a scanning
electron microscope. Kataoka et al. observed that the strength
and stiffness of the SGM samples increased with increase in the
number of curing days, and attributed this increase to the growth
and bonding of needle-like ettringite crystals within the SGM
sample pores caused by the curing process.
Jefferis and Lam discussed the use of polymers as an
alternative to bentonite in geotechnical construction fluids
(slurries). Polymers have several advantages over bentonite in
that polymer fluids require smaller preparation plants that can
access congested urban areas, require shorter preparation time,
and are environmentally less hazardous. In addition,
constructions made with polymers have better performance than
their bentonite counterparts. However, there are some
limitations of polymers like reduction of fluid properties due to
continued shear in recirculation systems and potential for loss of
properties in saline soils. Therefore, Jefferis and Lam
recommended that polymers should be used carefully with
proper monitoring.
37.0
37.5
38.0
38.5
39.0
39.5
40.0
0
0.5
1
1.5
Internal friction angle (deg.)
Decomposition rate of organic matter (%)
In order to investigate the reusability of in situ excavated soil
with poor mechanical properties, Blanck et al. studied the effect
of three non-traditional additives, an acid solution, an enzymatic
solution, and a lignosulfonate, on the compaction characteristics
and strength of silt. The test results showed that the acid
solution did not improve the compaction characteristics and that
adequate soil compaction can be achieved with low water
content using the enzymatic solution and lignosulfonate. Blanck
et al. concluded that enzymatic and lignosulfonate treatments
would reduce water usage in constructions.
3.2 Efficient use of geosynthetics
The use of geosynthetics can reduce resource consumption and
environmental impacts of geotechnical constructions, and can
prevent soil erosion (Herteen 2012, Jones and Dixon 2011).
Frischknecht et al. showed through life cycle assessment of
pavement drainage systems that constructions using
geosynthetics have less environmental impact.
Herteen et al. presented a general discussion on the use of
geosynthetics, particularly geogrids, and pointed out that
constructions with geosynthetics is more economical and
environment friendly than traditional alternatives. According to
Herteen et al., political reasons and population density and
distribution often dictate the construction choices related to the
national and international traffic routes within the European
Union (EU), and geosynthetics can be used to advantage in
many such constructions. The authors discussed about the use of
geosynthetics in slope stabilization, reinforced earth walls,
sound barrier walls, and embankments on soft clay, and pointed
out the beneficial features of geosynthetics. They also discussed
about the provisions given in Eurocode-7, German standards
and British standards regarding constructions related to
geosynthetics. Based on Herteen et al., it can be concluded that
efficient, economic, aesthetically pleasing, and environment
friendly constructions with minimal monitoring requirement are
possible using geosynthetics.
3.3 Sustainable foundation engineering
Foundations form an integral part of geotechnical constructions,
and sustainable design and construction of foundations are very
important for overall sustainable development (Basu et al.). As
part of sustainable foundation engineering, Basu et al.
advocated the use of proper constitutive models and appropriate
numerical analyses, adoption of reliability based design
approach (e.g., LRFD), incorporation of spatial heterogeneity of
soil in analysis and design, adoption of economical and
environment friendly construction practices, reuse and
retrofitting of existing foundations, and use of foundations in
harvesting wind and geothermal energy.
Bourne-Webb et al. presented a case study of piled raft
construction for a shopping center in Cambridge, UK as a cost-
effective, time-saving and resource-efficient alternative to
conventional pile foundations. Based on detailed site
