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Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
much reuse of existing geotechnical facilities as possible to
minimize waste. This approach aims at reaching a dynamic
equilibrium between engineering integrity, economic efficiency,
environmental effectiveness, and social acceptability and equity.
In an endeavor to incorporate sustainability in geotechnical
design, three new trends have been identified (Iai 2011): (i) geo-
structures are now designed for performance rather than for ease
of construction, (ii) designs are now more responsive to site
specific requirements, and (iii) the designs consider soil-
structure interaction rather than just analysis of structural or
foundation parts.
3 SUMMARY OF SUSTAINABLE GEOTECHNLOGY
RESEARCH
Several research studies have been performed that aim at
making geotechnical engineering practice sustainable. The areas
in which research has progressed include (1) the use of
alternate, environment friendly materials in geotechnical
constructions, and reuse of waste materials, (2) innovative and
energy efficient ground improvement techniques, (3) bio-slope
engineering, (4) efficient use of geosysnthetics, (5) sustainable
foundation engineering that includes retrofitting and reuse of
foundations, and foundations for energy extraction, (6) use of
underground space for beneficial purposes including storage of
energy, (7) mining of shallow and deep geothermal energy, (8)
preservation of geodiversity, and (9) incorporation of geoethics
in practice.
Geohazards mitigation is another important aspect of
sustainable geotechnical engineering
related studies include
studies on the effects of global climate change and of multi-
hazards on geo-structures. In this context, it is important to note
that sustainable geotechnical engineering should not only focus
on minimization of ecological footprints but also on making
geo-structures reliable and resilient so that the effects of
hazards, both natural and man-made, can be minimized. The
aspect of reliability and resilience is particularly important for
critical infrastructures (e.g., lifeline systems like transportation
and power supply network without which other systems like
cities cannot function) of which geo-structures like dams,
embankments, slopes and bridge foundations are important
components.
The recent research studies on geosustainability are mostly
based on the common notions of sustainability like recycling,
reuse and use of alternate materials, technologies and resources.
However, whether such new approaches are actually sustainable
or not cannot be ascertained without proper assessment using,
for example, whole life cost analysis and risk based
performance analysis. Therefore, a complete sustainability
assessment framework is necessary for geotechnical projects to
ascertain the relative merits of different options available for a
project.
Any geosustainability assessment framework should have a
life cycle view of geotechnical processes and products and
should (i) ensure societal sustainability by promoting resource
budgeting and restricting the shift of the environmental burden
of a particular phase to areas downstream of that phase, (ii)
ensure financial health of the stakeholders, and (iii) enforce
sound engineering design. As the uncertainties associated with
geotechnical systems are often much greater than those with
other engineered systems, sustainability framework for
geotechnical engineering should include an assessment of the
reliability and resilience of the geo-system, and offer flexibility
to the user to identify site specific needs.
From the environmental impact point of view, quantitative
environmental metrics like global warming potential (Storesund
et al. 2008), carbon footprint (Spaulding et al. 2008), embodied
carbon dioxide (Egan et al. 2010), embodied energy (Chau et al.
2006) and a combination of embodied energy and emissions
(carbon dioxide, methane, nitrous oxide, sulphur oxides and
nitrogen oxides) (Inui et al. 2011) have been used to compare
competing alternatives in geotechnical engineering. But,
assessing the sustainability of a project based solely on metrics
like embodied carbon dioxide or global warming potential
involves ad hoc assumptions, puts excess emphasis on the
environmental aspects and fails to consider a holistic view that
must also involve technical, economic and social aspects (Holt
et al. 2010, Steedman 2011).
Among the sustainability assessment tools that address the
multidimensional character of sustainability, some are
qualitative and represent the performance of a project on
different sustainability related sectors pictorially (e.g.,
GeoSPeAR) (Holt 2011). The second category of
multidimensional assessment frameworks consist of quantitative
and life cycle based tools. Life cycle costing (LCC), life cycle
assessment (LCA), multicriteria analysis and combinations of
LCC and LCA have been used for this purpose. Assessment
frameworks and metrics like Green Airport Pavement Index,
BE
2
ST-in-Highways and Environmental Sustainability Index
fall under this category (Pittenger 2011, Lee et al. 2010b, Torres
and Gama 2006).
The third approach to sustainability assessment is based on
point based rating systems that provide a measure of
sustainability of projects based on points scored in the different
relevant categories. Rating systems like GreenLites (McVoy et
al. 2010), I-LAST (Knuth and Fortman 2010), Greenroads
(Muench and Anderson 2009), MTO–Green Pavement Rating
System (Chan and Tighe 2010) and Environmental Geotechnics
Indicators (Jefferson et al. 2007) fall under this category.
4 SUSTAINABLE GROUND IMPROVEMENT
A major part of the sustainability related research in
geotechnical engineering has focused on ground improvement
through the introduction of novel, environment friendly
materials with particular emphasis on the reuse of waste
materials. Puppala et al. (2009) proposed the use of alternate
materials for soil stabilization including the use of recycled
materials in geotechnical constructions. Other examples include
the use of recycled glass-crushed rock blends for pavement sub-
base and recycling of shredded scrap tires as a light-weight fill
material.
Reuse of old pavements including asphalt and concrete
pavements has been on the rise (Gnanendran and Woodburn,
2003). The old pavements are recycled into full and partial
depth reclamation bases with cement or other additive
treatment. Sometimes these pavements are recycled into
aggregate materials which are termed as reclaimed asphalt
pavement (RAP) materials. RAP materials have been used as
bases with chemical stabilization, and several state DOT
agencies in the USA has been using them in the new pavement
construction projects. Puppala et al. (2009) performed a series
of resilient modulus tests on cement and cement-fiber treated
RAP for use as pavement base material. They reported that
the
structural coefficients increase with an increase in the confining
pressure and these values are higher for cement and cement–
fiber treated aggregates. The significant increase of structural
coefficients with cement-fiber treatment (30%) was attributed to
the tensile strength and interlocking properties offered by the
fiber content.
Investments made on transportation and processing is
reduced when native material after stabilization is used as a base
or backfill material. This saves money that might otherwise be
spent on fuels for transportation. The old pavement material if
cannot be reused has to be landfilled, which increases the costs
associated with the landfilling practices. Therefore, the use of
old pavement materials as stabilized bases reduces the space
used for landfills, which, in turn, reduces the overall carbon
footprint of the project by not using aggregates from quarries.
