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96ARTICLE
Sustainability and geotechnical engineering: perspectives and
review
Dipanjan Basu, Aditi Misra, and Anand J. Puppala
Abstract: The built environment serves as a dynamic interface through which human society and the ecosystem interact and
inﬂuence each other. Understanding this interdependence is a key to understanding sustainability as it applies to civil engineering. There is a growing consensus that delivering a sustainable built environment starts with incorporating sustainability
thoughts at the planning and design stages of an infrastructure construction project. Geotechnical engineering can signiﬁcantly
inﬂuence the sustainability of infrastructure development because of its early position in the construction process. In this paper,
the scope of geotechnical engineering towards sustainable development of civil infrastructure is reviewed. The philosophies and
deﬁnitions of sustainability as applicable to geotechnical engineering are discussed. A comprehensive review of the research and
case studies performed in geotechnical engineering, in relation to sustainable development, is presented in an effort to outline
the scope and goals of sustainable geotechnical engineering.
Key words: sustainability, geosustainability, resilience, reliability, geosystems.
Résumé : L’environnement bâti sert d’interface dynamique à travers laquelle la société humaine et l’écosystème interagissent
et s’inﬂuencent l’un et autre. La compréhension de cette interdépendance est la clé de la compréhension de la durabilité telle
qu’appliquée en génie civil. Il y a un consensus grandissant qui considère qu’un environnement bâti durable commence par
l’intégration de la pensée durable aux étapes de planiﬁcation et de conception d’un projet de construction d’infrastructure. Le
génie géotechnique peut inﬂuencer signiﬁcativement la durabilité d’un développement d’infrastructure en raison de la position
en début du processus de construction. Dans cet article, une revue de l’apport du génie géotechnique vers le développement
durable d’infrastructures civiles est présentée. Les philosophies et déﬁnitions de la durabilité applicables au génie géotechnique
sont discutées. Une revue détaillée de la recherche et d’études de cas réalisés en génie géotechnique et reliés au développement
durable est présentée aﬁn de déﬁnir les objectifs et buts du génie géotechnique durable. [Traduit par la Rédaction]
Mots-clés : durabilité, géodurabilité, résilience, ﬁabilité, géosystèmes.
Introduction
Sustainability of a system is its ability to survive and retain its
functionality over time. In very simple terms, sustainability deals
with the supplies (capacities) and demands (loads) in a system, and
as long as the supply is greater than the demand, the system
is sustainable. When put in a global perspective, the concept of
sustainability deals with the fundamental questions related to the
survivability and functionality of the physical world, and is therefore inextricably connected to social, environmental, economic,
and engineered systems. It is the interconnectedness of these systems that makes sustainability a complex concept because the
supplies and demands of one system affect the supplies and demands of the other systems. Time is an inherent aspect of sustainability, and questions related to sustainability must be addressed
by considering supplies and demands that change over time.
Engineered systems serve human societies by drawing resources
from nature and, in the process, generate emissions and wastes
that nature has to absorb. To be competitive, engineering products must be cost effective and have to function properly over
their design life. Clearly, engineered systems are inextricably
connected to the social, environmental, and economic systems.
Because humankind is heavily dependent on engineered systems —
from living in temperature-controlled houses to using cellular
phones — sustainability of the physical world is heavily dependent on the contributions of the engineered systems. Responsible
and ethical engineering practices can contribute towards a sustainable world through the development of reliable and robust
engineering products that are economically viable and ensure
social well-being, exploit the least amount of natural resources,
and generate the least amount of wastes.
The civil engineering industry has its footprints on all human
efforts to control, modify, and dominate nature and natural systems.
It is estimated that the construction industry accounts for about 40%
of the global energy consumption and depletes large amounts of
sand, gravel, and stone reserves every year (Dixit et al. 2010). Construction activities also add to the problems of climate change, ozone
depletion, desertiﬁcation, deforestation, soil erosion, and land, water, and air pollution (Kibert 2008). A geotechnical construction project not only has the aforementioned detrimental effects on earth’s
resources and environment but also changes the land use pattern
that persists for centuries and affects the social and ethical values
of a community. Thus, geotechnical projects interfere with many
social, environmental, and economic issues, and improving the
sustainability of geotechnical processes is extremely important in
achieving overall sustainable development (Jefferis 2008; Long
et al. 2009; Pender 2011). In fact, geotechnical design and construction, being placed early in a civil engineering project, can
Received 27 March 2013. Accepted 26 May 2014.
D. Basu and A. Misra. Department of Civil and Environmental Engineering, University of Waterloo, 200 University Avenue W., Waterloo, ON N2L 3G1,
Canada.
A.J. Puppala. Department of Civil Engineering, Box 19308, The University of Texas at Arlington, Arlington, TX 76019, USA.
Corresponding author: Dipanjan Basu (e-mail: dipanjan.basu@uwaterloo.ca).
Can. Geotech. J. 52: 96–113 (2015) dx.doi.org/10.1139/cgj-2013-0120
Published at www.nrcresearchpress.com/cgj on 11 June 2014.
Basu et al.
signiﬁcantly contribute to sustainable development by making
sustainable choices and setting a precedent for the remainder
of the project. Although the role of geotechnical engineering in
sustainable development is being increasingly recognized, there is a
general lack of understanding regarding how exactly geotechnical
processes can contribute to the overall sustainability of the world. At
the same time, there is a scarcity of geosustainability literature and
of an integrated framework for sustainable geotechnical practice
(Abreu et al. 2008).
The purpose of this paper is to connect the broader scope of
sustainable development with geotechnical engineering and to
present a review of the research done on different aspects of sustainability in geotechnical engineering. The deﬁnitions and concepts of
sustainability are introduced, and the different approaches for sustainable practices in engineering are discussed, with an aim to relate
sustainability to geotechnical engineering. In this regard, the concept of resilience is introduced, as it is closely related to engineering
sustainability, and the available resilience quantiﬁcation methods
are brieﬂy outlined. Further, the recent research studies in geotechnical engineering that contribute to sustainable development are
discussed. In addition, the available sustainability assessment frameworks in geotechnical engineering are reviewed. These varied topics
are integrated together in an attempt to deﬁne the scope and goals of
sustainable geotechnical engineering.
Sustainability, engineering, and geotechnology
Deﬁnitions and philosophies of sustainability and
connection to engineering
Brown (1981) described a sustainable society as “ … one that is
able to satisfy its needs without diminishing the chance of future
generations”. The Brundtland Commission (Brundtland 1987),
formed under the auspice of the United Nations, adapted the ideal
of Brown (1981) and deﬁned sustainable development as “development that meets the needs of the present without compromising
the ability of the future generations to meet their own needs”. The
deﬁnition by the Brundtland Commission carries a connotation of
time and takes into account intergenerational justice, but is often
criticized for being anthropocentric (Curran 1996), for having a negative connotation and for restricting the focus to a limited resource
use (Wood 2006). An alternative deﬁnition states that sustainability
is improving the quality of human life while living within the carrying capacity of the supporting ecosystem (IUCN/UNEP/WWF 1991).
This deﬁnition is less anthropocentric and emphasizes the supply
and demand concept mentioned previously.
Although the deﬁnitions in the preceding paragraph delineate
the scope of sustainability, they do not provide a deﬁnite pathway
to develop sustainable engineering practices or to solve engineering sustainability problems. In fact, the solution approach to sustainability problems has been a matter of debate and research
across different disciplines over a long period of time (Jefferis
2005). Often, this debate surfaces as the development of two fundamentally different approaches, namely, weak and strong sustainability. “Weak sustainability” assumes that natural capital is
replaceable by human capital or technological development as
long as the total capital base remains constant or increases (Arrow
et al. 2003), while “strong sustainability” (Daly 2005) advocates
against the decline of natural resources exclusively. Thompson (2010)
explained the debate as the difference between two philosophies,
namely, resource sufﬁciency and functional integrity. The “resource
sufﬁciency” approach has an anthropocentric view without any recognition of biodiversity or of the moral values of nonliving entities,
and determines the sustainability of a practice on how long the
practice could be carried on at the present rate of consumption. In
contrast, the “functional integrity” approach measures the sustainability of a practice based on the threat it creates to the reproducing capacity of a self-regenerating system, and supports the
97
“deep ecology” school of thought propagated by Næss (1949),
which states that the right of all forms of life to live is a universal
right and no particular species has more of this right than any
other species. Thus, there are two alternate views of sustainability: a
one-dimensional, anthropocentric view as advocated by weak
sustainability or resource sufﬁciency and a multi-dimensional,
all-encompassing view as supported by strong sustainability or
functional integrity.
In the engineering domain, Seager et al. (2011) identiﬁed two
different approaches that have been taken to solve the sustainability problems: (i) the business-as-usual approach and (ii) the
systems engineering approach. The business-as-usual approach to
sustainable engineering is essentially a one-dimensional, anthropocentric approach that relies on technological innovation and
upgrade as a solution to all problems — genetically modiﬁed
seeds for higher food production and nuclear power generation
for increased power demand are some examples. Seager et al.
(2011) pointed out that technological upgrade comes at a price that
is not affordable by most countries in the world, and hence, the
business-as-usual approach indirectly promotes social inequality
and injustice. Moreover, the long-term impacts of using innovative technologies are not always apparent, and further research is
required before these technologies can be used at a larger scale.
In the systems engineering approach, the design objective is to
minimize the cost of production with prudent use of resources
and with a constraint on harmful emissions (Gradel 1997, Kibert
2008) — thus the approach is economy centric, with some considerations for the natural environment. A problem with this approach is
that it is nearly impossible to arrive at a global consensus regarding what constitutes an optimal solution for any sustainability
problem (Seager et al. 2011). Even if a solution is decided to be
optimal, in moving from the stage of technological innovation to
the stage of optimization, the primary focus is on improving cost
efﬁciency rather than on sustainability. Again, as processes become cost efﬁcient, prices of commodities decrease, which increases mass consumption and consumption-driven production.
As production increases, resource consumption increases and so
does the related environmental impacts — these adversely affect
the sustainability agenda (Fiksel 2007).
A more recent approach to systems engineering is to incorporate the three Es — environment, economy, and equity — as
design objectives. This is in contrast to the optimization approach
described earlier in which cost is the design objective, and environmental impacts and social concerns act as constraints. The
three Es concept represents the multi-dimensional approach towards sustainability as advocated by functional integrity. A similar approach is practiced in public enterprises for full accounting
of environmental, social, and economic cost and beneﬁts using
the triple bottom line concept (Slaper and Hall 2011). Achieving a
balance of the three Es, however, is a difﬁcult task involving
tradeoffs because the three Es are often at conﬂict between themselves (Hempel 2009; Fig. 1). The most common conﬂict is between
the economic growth and environmental protection, and there is
also a conﬂict between economy and equity, which manifests
itself in an unequal distribution of wealth. The three Es approach,
however, has been criticized by Seager et al. (2011) for attempting
to deﬁne and solve sustainability problems at the process scale
whilst sustainability issues in reality have global implications.
Clearly, sustainability-related problems are complex, and according to Seager et al. (2011), sustainability problems are similar to “wicked problems” deﬁned by Horst Rittel in the 1960s
(Buchanan 1992). The concept of wicked problem was originally
put forward as an antithesis to the linear thinking process, which
assumes that solving any problem is a two-step process involving
problem deﬁnition and problem analysis (Buchanan 1992). Rittel
and Webber (1973) pointed out that, in multi-dimensional, multipartisan projects like planning or construction, different stakeholders may have different issues and concerns that are at conﬂict
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98
Fig. 1. Three aspects and conﬂicts of sustainable development.
with other stakeholders’ interests and priorities. In such cases, it
is difﬁcult to deﬁne a single problem that can address all the
issues of all stakeholders. Also, such issues and concerns generally
arise from the requirements and perceptions of the stakeholders
at that particular given time and situation, and these requirements may change over time. Thus, today’s solution may not remain relevant or may not be adequate at a future date. These
problems that suffer from both problem formulation issues and
temporal uncertainty were named wicked problems and are deﬁned as “class of social system problems which are ill formulated,
where the information is confusing, where there are many clients
and decision makers with conﬂicting values, and where the ramiﬁcations in the whole system are thoroughly confusing” (Buchanan
1992).
Sustainable engineering problems are wicked problems, as they
share the ﬁve most relevant characteristics of wicked problems:
(i) they are difﬁcult to formulate, (ii) multiple but incompatible
solutions exist, (iii) time frames are open-ended, (iv) the problems
are unique, and (v) competing value systems or objectives exist in
the problem. Such problems and their impacts transcend disciplines and processes, and hence, require a solution approach that
can bring about “integrations of signs, things, actions, and environments that address the concrete needs and values of human
beings in diverse circumstances” (Buchanan 1992).
Seager et al. (2011) suggested the use of a sustainability science
approach that aims at providing a global view for solving sustainable engineering problems. Conceptually introduced by Mihelcic
et al. (2003) and Kates et al. (2001), the sustainability science approach replaces the discipline-speciﬁc solution approach to sustainability issues with a global approach in which ideas and
concepts are drawn from all related ﬁelds of sustainability study
and then integrated into a solution for the sustainable engineering problem. The sustainability science approach requires that all
the stakeholders in the process should have an understanding
of the process and its impact, and should share an appreciation
of the global reach of the issues. For example, for infrastructure
construction projects to be sustainable, the construction engineer
should have enough knowledge about the impacts of the emissions and pollution created during the construction process and
about the regulations and policies concerning the emissions and
pollution, in addition to his or her usual knowledge of resource
consumption and safety. Also, to maximize social equity, it is
necessary to involve the people in the neighborhood of the construction site in decisions that concern their socioecological environment. To be able to participate meaningfully in the decision
process, all stakeholders should have sufﬁcient knowledge about
the different technological alternatives available for the construction process and about the impacts of these alternatives. Such
an approach requires dissemination and sharing of knowledge
across different disciplines and social categories, which facilitates
the understanding of the transdisciplinary and temporal nature
of sustainability issues (Mihelcic et al. 2003).
Can. Geotech. J. Vol. 52, 2015
Seager et al. (2011) and Mihelcic et al. (2003) suggested introducing sustainability science approach to the engineering curriculum
so that the future engineering community develops an appreciation for the global reach of the sustainability problems and can
use the aforementioned, holistic approach to solve these problems. However, because the sustainability science approach is still
under development, at present, the systems engineering approach of balancing the three Es seems to be the most promising
approach for sustainable engineering at the project scale.
Reliability, resilience, and adaptability as part of
sustainable engineering
For any infrastructure engineering project, ensuring the safety,
serviceability, and reliability of a facility or product is as important as balancing the three Es. A design with too much focus on
the environmental impact or economy may lead to a marginally
safe and “efﬁcient” structure without any scope for redundancy
(in this context, efﬁciency relates to frugal design with minimal
use of resources and money, while redundancy refers to extra
provisions that may become useful if design loads and stresses are
exceeded). Such a design may readily fail under unprecedented
and unanticipated external threats (Chateauneuf 2008) and does
not support the sustainability agenda. The lack of resilience
against unaccounted external forces and threats is often not acceptable in civil engineering particularly for those structures that
are part of critical infrastructures. Geostructures are often important components of critical infrastructures, and hence, thoughts
on sustainability in geotechnical engineering should include the
reliability and resilience aspects of engineering design. Thus, in
the civil and geotechnical engineering domains, sustainability
can be looked upon as a dynamic equilibrium between four Es —
engineering design, economy, environment, and equity, as described in Fig. 2.
Reliability of a structure is a measure of its safety against possible identiﬁed failure states — reliability-based design ensures
that the structure is sufﬁciently away from its identiﬁable failure
states so that it can perform its intended set of functions under
predicted external loads. Traditionally, reliability-based design
has been used in critical infrastructures like transportation – road
construction networks, water supply networks, or power supply
networks. Critical infrastructures are deﬁned as the lifeline systems like transportation and power supply networks without
which other systems (e.g., cities) cannot function (O’Rourke 2007).
Therefore, the safety and reliability of such critical infrastructures
are of paramount importance to the social and economic wellbeing of a region or country.
Geostructures like embankments, slopes, and bridge foundations are important components of critical infrastructures like
transportation networks, while dams are critical infrastructures
themselves (O’Rourke 2007). Failures in any of them can initiate
complete or partial loss of functionality of other related structures
and systems and can severely impact the social and economic infrastructure of any country. Geotechnical engineering also has a prominent role in waste containment — a geotechnical failure in a landﬁll
system can be both socially and environmentally disastrous, with
spreading and leaching of contaminants. Moreover, unlike structural systems that handle uncertainties related mostly to external
loads, geotechnical engineering suffers from signiﬁcant uncertainties related to soil and rock properties in addition to uncertainties in
external loads (Long et al. 2009). Further, material properties in
geotechnical design may alter due to a change in the surrounding
environment (e.g., a contamination can alter the soil properties, and
permafrost can get degraded due to climate change) and can add to
the uncertainties in the system. Therefore, reliability-based design
should be an essential part of sustainable geotechnical design.
The underlying assumption in reliability-based design is that
the failure states can be predicted and the associated probabilities
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Basu et al.
99
Fig. 2. Four Es of sustainability in engineering projects.
of failure can be estimated (risk-based or “fail-safe” design). In
recent times, there is a growing consensus that it is not entirely
possible to anticipate the likelihood, manifestation, and consequences of all future threats (i.e., failure states), and hence, safety
measures are always inadequate (Simoncini 2011; Vugrin et al.
2011). For example, Rogers et al. (2012) pointed out eight categories
of possible threats that the physical civil infrastructure may encounter: (i) gradual deterioration from aging, exacerbated by adverse
ground conditions (including chemical, biological, and physical
threats); (ii) damage due to surface loading or stress relief due to
opencut interventions; (iii) severely increased demand, and everchanging (different, or altered) demands; (iv) terrorism; (v) the effects
of climate change; (vi) the effects of population increase, including
increasing population density; (vii) funding constraints; (viii) severe
natural hazards (extreme weather events, earthquakes, landslides,
etc.). Although designs should be made ﬂexible and robust to ward
off as many threats as possible, it is impossible to design engineering
systems that are foolproof against all possible threats. Therefore, for
systems to be sustainable, it is necessary to ensure that the system is
inherently capable of bouncing back to its functionality irrespective
of the nature or magnitude of shock or distress it is subjected to.
Such systems are called resilient systems. The resilience of a system is
deﬁned as its ability to return to its original “state” after a perturbation without any “regime change” (Holling 1996, 2001; Walker and
Salt 2006). Resilience is particularly important for interconnected
systems where a failure in any part can quickly propagate to other
parts and can easily trigger a system failure (Park et al. 2011). Geostructures are often an integral part of critical infrastructure systems; therefore, resilience must be incorporated in geotechnical
engineering designs. For infrastructure systems, Bruneau et al. (2003)
chose four parameters (four Rs) as measures of community resilience: (i) robustness, as deﬁned by the capacity of the system or its
parts to perform its function even under external disturbance; (ii) redundancy, as measured by the degree to which an affected part is
substitutable; (iii) resourcefulness, deﬁned as the ability to identify
threats and set up plans for handling such threats; and (iv) rapidity
with which external disturbances are addressed. Rogers et al. (2012)
made an important distinction between resistance and resilience:
resistance relates to design and activities concerned with prevention
and protection of a system, while resilience relates to response and
recovery after a disruptive event reduces the functionality of the
system. Reliability-based design discussed previously can ensure adequate resistance in a structure or system, but resilience requires
additional considerations as discussed in the following.
Fig. 3. Loss of resilience in community as function of time.
The concept of resilience is far-reaching, and in order for a society
to be resilient, several aspects of resilience across disciplines have to
be explored. For example, Rogers et al. (2012) considered the resilience of ecological, economic, physical infrastructure, community,
and government systems together for a holistic conceptualization of
resilience from an interdisciplinary perspective. In a similar approach, Bocchini et al. (2014) considered four dimensions of resilience, namely, technical, organizational, social, and economic, and
further pointed out three beneﬁcial outcomes of resilience considerations: more reliability, faster recovery, and lower consequences.
Thus, resilience is not only related to the resilience of engineering
structures (hard resilience) but also to the community it affects (soft
resilience) as described earlier in the text (Miao and Banister 2012). In
fact, resilience is inherently related to social vulnerability (Phillips
et al. 2009), and geotechnical designs, particularly those against disasters and unprecedented events, must take into consideration the
plights of the vulnerable communities within a society.
Bruneau et al. (2003) quantiﬁed the loss of resilience of a community due to earthquake as the total expected degradation of
a chosen time-dependent performance function Q(t) (where t is
time) summed over a period of time (Fig. 3). Mathematically, the
loss of community resilience R is expressed as
冕
tr
(1)
R⫽
[100 ⫺ Q(t)] dt
td
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100
Can. Geotech. J. Vol. 52, 2015
Fig. 4. Resilience as function of time.
where td is the time at which disruption happens, and tr is the
time at which full or partial but stable functionality is restored
(Fig. 3). Henry and Ramirez-Marquez (2011) proposed a similar
approach to deﬁne resilience of a system as a function of time.
They suggested using a quantiﬁable and time-dependent ﬁgureof-merit or system-level performance function F(t) (e.g., ﬂow, delay, connectivity, etc.) for measuring resilience of the system
(Fig. 4). Because of a disruptive event, the value of F(t) may decrease, and how much F(t) recovers after remedial actions are
taken or whether F(t) attains its original value after system recovery is a measure of its resilience. Mathematically, resilience ᑬ is
deﬁned by Henry and Ramirez-Marquez (2011) as
(2)
ᑬ(t) ⫽
Fig. 5. System regime change due to loss of resilience.
F(tr) ⫺ F(td)
F(t0) ⫺ F(td)
where t0 is the initial time (i.e., the time when there was no
disruption), td is the time at which disruption stops (after its start
at te) and the system is at its minimal performance level, tr is any
time after the time td at which the system starts recovering (Fig. 4).
ᑬ < 1 during the time tf – td over which the system recovers and attains a stable constant value at t = tf. ᑬ = 1 if the system attains full functionality (i.e., if F(tr) = F(t0)) at t = tf. Thus, in contrast with traditional fail-safe approach of design, resilience-based design can be looked upon as a “safe-to-fail” approach in which the systems are expected to fail under unexpected stressors and aims at containing the failure and recovering from the failure with least impact (Ahern 2011). For infrastructure systems, Bocchini et al. (2014) presented an integrated approach for sustainability and resilience considerations in design through a probabilistic framework in which the expected life cycle impact of an infrastructure on a community is considered to be a sum of impacts from regular events (e.g., construction, normal operations, scheduled maintenance, and deconstruction) multiplied by their corresponding probabilities of occurrence and of impacts from extreme events (e.g., natural disaster and terror attacks) multiplied by their corresponding probabilities of occurrence. In addition to sudden external shocks, a system may also lose its resilience over time because of slow and natural changes in its own properties and in its environment. As shown in Fig. 5, a system is most resilient when it is at state 1 and its resilience decreases as it moves through states 2 and 3. The vertical axis of Fig. 5 can be thought to represent the “potential energy” of the system, with the minimum energy representing the most stable state as is true for mechanical systems. At state 3, even a small amount of external perturbation (or addition of energy) can cause a change of that state. The change from state 1 to state 3 is often gradual and natural, and hence, may not be captured in a system designed only to respond to sudden external shocks. Therefore, sustainable designs must perform checks against resilience (Lombardi et al. 2012) both from sudden shocks and from gradually changing demands and properties of systems in a multi-disciplinary framework. Adaptive capacity of a system ensures that such slow and gradual changes are recognized by the system and managed effectively, so that the system does not get close to stage 3. Thus, adaptability of a system can help manage its resilience. An adaptable system may preserve the diverse elements in a system, increase the redundancy and ﬂexibility of the system, and may be more capable of absorbing external unpredicted disturbances without any signiﬁcant loss of functionality (Folke et al. 2002). An engineered system can be deemed adaptive when it is managed in a way such that it is responsive to slow changes in its own fundamental properties (e.g., strength of the material) and in its environment (e.g., change in ﬂooding frequency). With an adaptive management strategy, an engineered system is better equipped to handle changes in demands over time and is therefore more efﬁcient. For example, if a levee system is monitored for change in Published by NRC Research Press Basu et al. rainfall pattern over time and in the rainfall-induced ﬂooding pattern in the region, and required modiﬁcations in the levee system are undertaken from time to time, then the system becomes less susceptible to failure from increasing ﬂood levels. Such an adaptive management of engineered system ensures the safety, reliability, and longer life of the system, which eventually leads to less resource consumption and to social and economic beneﬁts. Sustainability and geotechnology It is evident from the foregoing discussion that sustainability is a multi-scale, multi-disciplinary, and multi-dimensional paradigm that aims at ensuring the well-being of the living and nonliving world for the current and future generations. Geotechnical engineering, being discipline speciﬁc, cannot solve global sustainability problems completely, but can contribute towards their solutions. Geostructures and geooperations often form important interfaces between the built and natural environments, and interact with and affect a wide variety of externalities — for example, dams and levees buffer the ﬂuctuations in hydrologic cycles and affect water movement across political boundaries, extraction of petroleum resources from the subsurface affects the natural environment and global economy, and landﬁll systems prevent contaminants from reaching groundwater across regional scales. Further, geotechnical engineering has a very important role in mitigating or containing disasters, and failure to do so is often catastrophic to society — for example, breach of a levee system during a hurricane or tsunami has far-reaching consequences on the civil infrastructure and society, breakdown of underground water pipelines caused by soil liquefaction during an earthquake can signiﬁcantly reduce the ability to mitigate widespread ﬁre that may occur as an aftermath of earthquakes, improper or lack of slope management can cause rainfall or earthquake-induced landslides that can wipe out communities and affect regional transportation networks, and terror attacks on underground transit systems by bomb blast can lead to collapse of the physical infrastructure and heavy loss of life. Thus, geotechnical engineering has a wide gamut and a global reach, and can inﬂuence the sustainable development of infrastructure and civil societies in a signiﬁcant way (Fig. 6). Sustainable geotechnics can therefore be thought of as a subdiscipline focusing on geotechnical engineering practices that reverse (at least partially) the detrimental effects of past geotechnical practices on nature and society, and ensure the well-being of society and natural environment at all times. It should not only include environment-friendly practices that are cost effective and cause minimal ﬁnancial burden to the present and future generations, but also promote reliability- and resilience-based analysis and design, and adaptive management strategies so that social vulnerability is minimized and overall well-being is upheld. Sustainability assessment should also be a part of sustainable geotechnical practices to ensure that sustainability goals are indeed achieved. A report entitled “Geological and geotechnical engineering in the new millennium: opportunities for research and technological innovation” by the US National Academy of Sciences mentioned seven categories where geotechnical engineering can contribute to improve the sustainability of the societal system (Long et al. 2009). These include (i) waste management, (ii) infrastructure development and rehabilitation, (iii) construction efﬁciency and innovation, (iv) national security, (v) resource discovery and recovery, (vi) mitigation of natural hazards, and (vii) frontier exploration and development. Pantelidou et al. (2012) reviewed the applicability and importance of the seven sustainability objectives for geotechnical engineering that were originally developed for buildings by ARUP (2010). These include (i) energy efﬁciency and carbon reduction, (ii) materials and waste reduction, (iii) maintaining natural water cycle and enhancing natural watershed, (iv) climate-change adaptation and resilience, (v) effective land use and management, (vi) economic viability and whole life cost, and (vii) positive contribution to society. Based on Long et al. (2009) and Pantelidou et al. (2012) and on a similar list by Basu et al. (2013), the topics that can 101 be considered to be a part of sustainable geotechnical engineering can be listed as follows: (i) use of alternate, environment-friendly materials and reuse of waste materials in geotechnical construction (e.g., use of construction and demolition wastes in pavement subgrade); (ii) innovative, environment-friendly and energy-efﬁcient geotechnical techniques for site investigation, construction, monitoring, retroﬁtting, ground improvement, and deconstruction (e.g., bioslope engineering and use of natural ﬁber in soil reinforcement); (iii) retroﬁtting and reuse of foundations and other geotechnical structures; (iv) use and reuse of underground space for beneﬁcial purposes like pedestrian pathways, public transit, and water distribution system, and for storage of energy, carbon dioxide, and waste products; (v) characterization, analysis, design, monitoring, repairing, and retroﬁtting techniques in geotechnical engineering that ensure or contribute to reliability (robustness and resistance) and resilience; (vi) geotechnical techniques involved in the discovery and recovery of geologic resources like minerals and hydrocarbons, and in exploitation of renewable energy sources, such as shallow and deep geothermal, solar, and wind energies; (vii) geotechnical techniques for pollution control and redevelopment of brownﬁelds and other marginal sites; (viii) mitigation of geohazards (e.g., landslides, earthquakes, and blast) that also include the effects of global climate change; (ix) environmental and socioeconomic impacts from geoactivities, for example, from mining and petroleum extraction, dam construction, and waste disposal; (x) practice of geoethics and geodiversity; and (xi) development of sustainability indicators and assessment tools in geotechnical engineering. It is important to recognize that sustainability outcomes from a civil engineering solution can be ensured in two ways: by doing the right project and by doing the project right (ISI 2013). Choosing the right project often depends on the owner and policy makers, and is often beyond the scope of the civil and geotechnical engineers, although they can provide their inputs in the decisionmaking process. In fact, choosing the right project can have a signiﬁcantly greater chance of success from a sustainability standpoint than completing the project using good engineering that follows appropriate sustainability guidelines. The earlier the sustainability objectives are considered in a project, the better the outcome because the availability of sustainable alternatives decreases as a project proceeds from the planning to the execution stage (Fig. 7) (Pantelidou et al. 2012). For example, in a building foundation project, there can be a choice of foundation types at the planning stage, while the choice is limited to the materials to be used in the design stage; and in the execution stage, the choice is limited to the machinery used. Therefore, to achieve maximum beneﬁt from sustainability considerations, it is necessary to incorporate sustainability objectives at the planning and design stages of a project (Misra and Basu 2011). The analysis framework of Lombardi et al. (2011) on the critical sequencing of sustainabilityrelated actions and decisions within a project to obtain the most sustainable solution through a series of compromises in the design process can be adopted in geotechnical projects. On a project level, the following steps can positively contribute to a sustainable geotechnical solution: (i) involving all the stakeholders (e.g., owner, lawmakers, engineers, architects, users, and members of the affected community) at the planning stage of the project so that a consensus is reached regarding the steps to achieve a sustainable solution (such as control of pollution during and after construction, ﬁnancial impact on the affected community, choice of environment-friendly materials, aesthetic acceptability, acceptability of the project to the local community, etc.), and in subsequent stages to maintain transparent ﬂow of information and to gain consensus on any required change from the initial plan; (ii) proper site characterization so that the geologic uncertainties and associated hazards are minimized; (iii) robust and reliable analysis, design, and construction that involves minimal ﬁnancial burden and inconvenience to all the stakeholders; (iv) optimal use of materials and energy in planning, design, Published by NRC Research Press 102 Can. Geotech. J. Vol. 52, 2015 Fig. 6. Impacts and inﬂuences of geotechnical engineering. Fig. 7. Typical steps in geotechnical projects (modiﬁed from Pantelidou et al. 2012). Published by NRC Research Press Basu et al. construction, and maintenance of geotechnical facilities; (v) use of materials and methods that cause minimal negative impact on the ecology and environment; (vi) reuse of existing geotechnical elements (e.g., foundations and retaining structures) to minimize wastage; (vii) appropriate and adequate instrumentation, monitoring, and maintenance to ensure proper functioning of the facility; and (viii) performing adequate checks against resilience (which may include engineering, social, economic, and ecological resilience) and redesigning if necessary. This approach can contribute towards balancing engineering integrity, economic efﬁciency, environmental quality, and social equity as part of a sustainable geotechnical solution. Review of studies related to sustainable geotechnology In this section, the recent studies related to sustainable geotechnics are reviewed in the context of the theories and philosophies of sustainability described earlier in the text. The use of the word sustainability and its several variations has become commonplace in geotechnical and civil engineering parlance, and often the implications of sustainability are wrongly attributed to only environmental impact or carbon emissions. It is important to recognize that sustainability has multiple dimensions because of which the following review will assess the legitimacy of these studies in the context of the multiple dimensions of sustainability. Several geotechnical research studies and practical projects have been performed in the recent past that can be considered to contribute towards sustainable development. The scope of these studies and projects fall within the 11 categories mentioned in the previous section. A large number of these studies are based on the common notions of sustainability like recycling, reuse, and use of alternative materials, technologies, and resources. However, whether such new approaches actually lead to sustainable solutions or not must be assessed properly. For example, Clift and Wright (2000) have questioned the economic and environmental sustainability of recycling and reuse. They argued that the aim of end-of-life management should not only include removal of hazardous materials but also include minimization of the environmental impact. Reverse logistics studies in the UK and Sweden showed that the beneﬁts of recycling are largely offset by the environmental impact of transporting back used materials, and the practice may be unsustainable economically and environmentally for low-cost, low-reusability materials (Clift and Wright 2000). Thus, a complete sustainability assessment framework is necessary for geotechnical projects to ascertain the relative merits of different options available for a project. Considering the aforementioned, the literature review is divided into three parts. In the ﬁrst part, studies that contribute in one or more ways to sustainable development are reviewed. In the second part, the sustainability evaluation methods related to geotechnical engineering are discussed. The third part presents a critical appraisal of the studies presented in the previous two parts. The review is restricted to a few broad areas of geotechnical engineering that are most relevant to sustainable development. Figure 8 gives a summary of the literature review on geosustainability. Geotechnical studies for sustainable development As geotechnical engineering uses natural and manufactured raw materials in large quantities, a signiﬁcant part of the sustainabilityrelated research in geotechnology has focused on introducing new, environment-friendly materials and on reuse of waste materials. This branch of geotechnical engineering has existed for long in the form of geoenvironmental engineering. However, the traditional environment-related focus is slowly widening, and a life cycle view is often considered in recent geoenvironmental-related projects (Praticò et al. 2011). 103 The reuse of industrial wastes in pavements is a major area of research in transportation geotechnics. Extensive literature is available on the use of ﬂy ash and bottom ash in concrete mix for roads and highways (Kim et al. 2005; Chrismer and Durham 2010; O’Donnell et al. 2010; Solis et al. 2010), off-speciﬁcation ﬂy ash for strengthening soil rubber mix for use as pavement base (Wiechert et al. 2011), shredded scrap tires as a lightweight ﬁll material in pavement embankments (Humphrey and Blumenthal 2010; Voottipruex et al. 2010), recycled asphalt shingles in pavement mixtures (Cascione et al. 2010; Watson et al. 2010; Thakur et al. 2011; Warner and Edil 2012), spent blast abrasives in hot mix asphalt (Mattei and Khanfar 2008), blast-furnace slag and ﬂy ash as cohesive nonswelling soil cushion (Rao and Sridevi 2011), cementstabilized quarry ﬁnes as pavement bases (Saride et al. 2010), recycled glass-crushed rock blends for pavement subbase (Ali et al. 2011), ﬁne recycled glass as a sustainable alternative to natural aggregates (Disfani et al. 2011), and foundry sand in roadway subbase (Bradshaw et al. 2010). Anochie-Boatang and Tutumluer (2011) developed material characterization techniques, performance models, and laboratory procedures for determining the suitability of oil sands as road building materials. A study is underway in southern Nigeria in which cement kiln dust is used to improve the strength of highly erosive soil for road construction (Oduola 2010). Apart from transportation geotechnics, there are other areas where alternative materials have been used. Vinod et al. (2010) studied the use of lignosulfonate, which promotes surface vegetation and natural subsurface fauna, for soil stabilization. Leong (2006), Storesund et al. (2008), and Wu et al. (2008) recommended the use of bioengineering and geosynthetics to make slopes sustainable. The National Cooperative Highway Research Program (NCHRP) report on “Cost-effective and sustainable road slope stabilization and erosion control” (NCHRP 2012) also suggested using soil bioengineering for slope stabilization because of its cost effectiveness and enhanced erosion resistance. Yim (2004) suggested the use of new materials and innovative technologies for environmental sustainability in the post-construction use of slopes. Sridharan and Prakash (2008) performed research studies on the beneﬁcial use of otherwise hazardous coal and ﬂy ash in different geotechnical constructions. Patel and Bull (2011) considered the use of pulverized ﬂy ash for improvement of the thermal properties of energy piles. Meegoda (2011) studied the use of recycled mixed glass and plastic for segmental retaining wall units. The Environment Protection Authority (EPA Victoria, Australia 2009) recommended the use of biosolids as geotechnical ﬁll material, provided proper testing and characterization of the biosolids are done. Innovations in ground improvement projects can contribute to sustainable development. The use of solar-powered prefabricated vertical drains (Indraratna et al. 2010; Pothiraksanon et al. 2010) and improvement of the mechanical and hydraulic properties of soil using in situ soil bacteria through biomineralization and biopolymerization (Yang et al. 1992; DeJong et al. 2006; Fauriel and Laloui 2011; Inagaki et al. 2011) are some examples of innovative ground improvement techniques. Spaulding et al. (2008) compared, using three case studies, the use of ground improvement techniques as an alternative to conventional deep foundations in an attempt to reduce the environmental impact. In the ﬁrst case study, the use of dynamic compaction was compared with excavation and engineered ﬁll. In the second case study, controlled modulus columns under slab-on-grade were compared with driven piles. In the third case study, a cement–bentonite cutoff wall was compared with a soil–bentonite cutoff wall. The authors concluded that, in all the cases, the alternatives of ground improvement provided better economy and reduced the carbon footprint, mostly due to the use of low-embodied-energy materials like ﬂy ash. Egan and Slocombe (2010) also compared the use of ground improvement techniques, particularly, vibro-replacement stone columns, as an alternative to traditional deep foundations and concluded that stone columns are better from the environmental loading standpoint and that further reduction in the loading is Published by NRC Research Press 104 Can. Geotech. J. Vol. 52, 2015 Fig. 8. Summary of geosustainability literature review. possible if recycled materials and aggregates are used in vibro stone columns. The use of geosynthetics has been shown to reduce the environmental impacts of geotechnical construction (Heerten 2012). Jones and Dixon (2011) reported a study by the Waste and Resources Action Program (WRAP) in the UK that compared several designs using traditional concrete and steel with alternative designs using geosynthetics. The designs were compared based on their embodied energy consumption, and it was found that, in all the cases, the use of geosynthetics led to less consumption of embodied energy. Similar results were obtained by Heerten (2012) for two projects, a new district road project and a slope protection project, on the basis of their cumulative energy demand and carbon dioxide emissions over their entire life cycle. Stucki et al. (2011) showed that geosynthetics have less environmental impact than conventional geomaterials when used in ﬁltration, road construction, landﬁlls, and slopes. Heerten and Werth (2010) proposed to improve the safety of levees against soil erosion through the use of different geosynthetics in the levee cross section. Reuse and retroﬁtting of foundations is a traditional practice for almost all refurbishment projects, but recently, the concept has been extended for redevelopment projects as well (Butcher et al. 2006a). Strauss et al. (2007) identiﬁed eight factors that drive this change in practice: (i) location; (ii) archaeology and historical constraints; (iii) geological conditions and constraints; (iv) sustainability and material reuse; (v) land value and cash ﬂow projections; (vi) construction costs; (vii) consistency in building locations; and (viii) approvals and development risk. Reuse of foundations is an attractive option because the cost of removal of an old foundation is about four times that of construction of a new pile, disturbance to adjacent structures caused by foundation removal can be avoided, and backﬁlling of voids created by the removed foundation is not required (Butcher et al. 2006a). Several case studies demonstrating the beneﬁts of reuse of foundations have been documented (Anderson et al. 2006; Butcher et al. 2006b; Katzenbach et al. 2006; Tester and Fernie 2006). A case study of an idealized redevelopment of an ofﬁce building, documented by Butcher et al. (2006a), compares the whole life cost of the different design options for foundations — design for partial reuse, design for no reuse, and design for full reuse. The study shows that foundations designed for reuse have a much lower whole life cost than foundations designed without the reuse option, although the initial premium is slightly greater for foundations designed for reuse. Butcher et al. (2006a) also found that the embodied energy consumed in reusing foundations is nearly half of that consumed in installing new foundations. Leung et al. (2011) developed an optimization algorithm for reuse of pile foundations to obtain the best conﬁguration of new piles to be used alongside the existing piles so that the superstructure loads are safely transferred and, at the same time, material use is minimized. Another important contribution of geotechnical engineering to sustainable development is the utilization of underground space for housing and facilities. The International Tunnelling and Underground Space Association Committee on Underground Space (ITACUS 2011a) and Asadollahi and Zeytinci (2011) remarked that Published by NRC Research Press Basu et al. the use of underground space helps in preserving land for further expansion and development of facilities by future generations. Underground space is being utilized by many countries like Hong Kong, Japan, Singapore, Canada, Denmark, and Norway for different reasons like severe weather and topography (Rogers 2009). The city of Helsinki in Finland developed a master plan for underground use of space that divides the available space into ﬁve categories: (i) community technical systems; (ii) trafﬁc and parking; (iii) maintenance and storage; (iv) services and administration; and (v) unnamed rock resource (ITACUS 2011b). The Norwegian Tunnelling Society provides examples of sustainable use of underground spaces ranging from powerhouses for hydropower projects (Broch 2006) and underground telecommunication centers (Rygh and Bollingmo 2006) to storage of hydrocarbons (Grov 2006), and wastewater treatment plants (Neby et al. 2006; Ronning 2006). Underground structures like tunnels play an important role in water supply systems and in the transportation sector (Roberts 1996). The use of underground space for mass storage of food, liquid, and gas is also gaining popularity in many countries across the world (Roberts 1996). Rock caverns are in use for mass transit systems in Hong Kong, e.g., the Taikoo Cavern Station (Swales et al. 2011). Enhanced security, lessened environmental burden, increased energy efﬁciency, ease of maintenance due to less atmospheric exposure, enhanced protection against human-inﬂicted and natural calamities, less interruption to trafﬁc and city life, and better economy have been cited as some of the beneﬁcial effects of use of underground space (Sterling et al. 1983; Carmody and Sterling 1985). Jefferson et al. (2009) suggested locating the transportation infrastructure and utility infrastructure of Birmingham Eastside underground to reduce the load on land use and to reduce the environmental effects of emissions. Fragaszy et al. (2011) pointed out that underground space can be efﬁciently used in storing energy, particularly renewable energy like solar, tidal, and wind energy, which are characterized by intermittent supplies with seasonal or diurnal ﬂuctuations in production. Underground space can be successfully used for compressed air energy storage (CAES) (Pasten and Santamarina 2011). In fact, Kim et al. (2012) showed that the use of rock caverns for CAES can be more energy efﬁcient and environment friendly than other energy storage options. Storage of atmospheric carbon dioxide as well as pre- and post-combustion carbon dioxide from power plants in subsurface formations (Stevens et al. 2008; Firoozabadi and Cheng 2010) is another example of sustainable use of underground space that has a potential to reduce the greenhouse gas related effects on earth’s climate. A report entitled “Underground engineering for sustainable urban development” by the National Academy of Sciences outlines the scope of underground engineering for sustainable development (Gilbert et al. 2012). Geotechnical engineering has a prominent role in the alternative energy sectors like geothermal. Case studies show that deep foundations can be used as energy storage and transmitting elements (Quick et al. 2005), while concrete surfaces in contact with the ground (e.g., pavements and basement walls) can act as heat exchangers (Brandl 2006). The role of geotechnical engineering in promoting geothermal energy includes developing inexpensive and novel methods for drilling and trenching, understanding and using the thermal properties of soil and backﬁll materials, understanding the effect of thermal cycles on the behavior of energy piles, developing modeling tools and design methods for thermal load balancing to prevent long-term temperature changes in the densely populated areas, and understanding the limits of extractable energy for vertical and horizontal ground source heat pumps (Fragaszy et al. 2011). Research is in progress to develop proper characterization, analysis, and design of energy-related geostructures like energy piles (Abdelaziz et al. 2011; Laloui 2011; Peron et al. 2011; Wang et al. 2011). Geohazards mitigation is an important aspect of sustainability in geotechnical engineering. Yasuhara et al. (2011) cautioned that the probability of occurrence of combined geohazards (e.g., heavy 105 rainfall and earthquake occurring simultaneously) has increased due to climate-change effects and suggested measures like the use of geosynthetics, development and economic evaluation of adaptive technologies, and innovations in the design of geostructures to mitigate such hazards. The effects of climate-change-induced degradation of permafrost have been considered in the assessment of stability and functionality of road embankments. The degradation of permafrost induces differential settlement and dip in road embankments — improvement of the insulation capacity of soil to preserve the permafrost and improvement of soil strength using different ground improvement methods have been proposed as possible remedies (Ciro and Alfaro 2006). Harris (2005) studied the effect of permafrost degradation on mountain slope stability and concluded that traditional approaches to landslide hazard prediction may not be adequate for climate-changetriggered loss of permafrost. The biological and engineering impacts of climate change on slopes (bionics) project undertaken in the UK concluded that climate change, because of its effects on soil water content and vegetation type, impacts slope stability (Kilsby et al. 2009). Similar conclusions were made by Hughes et al. (2009) based on a full-scale test of a typical UK infrastructure slope. Glendinning et al. (2009) advocated the use of a proper management system for infrastructure slopes because of the complex interaction between roadside vegetation and soil. According to Andersson-Sköld et al. (2008), subsurface contaminant transport is also affected by climate change because of the ﬂuctuations in the groundwater table caused by climate-change-induced disasters like ﬂoods and landslides. Geodiversity is another important aspect of geosustainability. Geodiversity refers to the variety of materials (e.g., minerals, rocks, sediments, and soil), forms, and processes that form the earth (Osborne 2000). As part of sustainability efforts, preservation of the geodiversity (more aptly referred to as geoheritage) and ensuring that anthropological activities have minimal detrimental impact on it is essential. According to Prosser et al. (2010), geodiversity is impacted by natural hazards, and loss in geodiversity occurs more from the lack of ﬂexibility in human efforts to control the natural disasters than from the disasters themselves. Prosser et al. (2010) suggested that a proper understanding of the geomorphological processes and of their sensitivity to changes and efforts to conserve rather than prevent is necessary to preserve geodiversity. Geoethics is another aspect of geosustainability that is gaining importance, particularly in disaster management and geohazard mitigation. Geoethics draws its principles from geosciences, sociology, and philosophy (Limaye 2012) and is deﬁned as the “study and promotion of the evaluation and protection of the geosphere” (Peppoloni and Capua 2012). Geoethics deﬁnes a code of practice for geoscientists who act as interpreters between nature and people (Peppoloni and Capua 2012). Incorporating geoethics in projects can encourage development of practices that restrict overuse of natural resources, are acceptable to society, and are economically viable for the investor (Limaye 2012). Geoethical activities include reliably predicting natural hazards, informing people about possible natural hazards and educating them about ways of mitigating the hazards (Parkash 2012), and disseminating knowledge that may encourage people to conserve natural resources and geodiversity. Although ethical practices are necessary for sustainable development, application of the geoethical principles to real life situations is often very complicated (Lambert 2012; Limaye 2012). Sustainability assessment tools in geotechnology Any geosustainability assessment framework should have a life cycle view of geotechnical processes and products (Dam and Taylor 2011) 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 Published by NRC Research Press 106 Can. Geotech. J. Vol. 52, 2015 Fig. 9. SPeAR template. (iii) enforce sound engineering design and maintenance. As the uncertainties associated with geotechnical systems are often much greater than those with other engineered systems (Barends 2005), a sustainability assessment framework for geotechnical engineering should include an assessment of the reliability and resilience of the geosystem, 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 (Chau et al. 2008, Egan and Slocombe 2010), embodied energy (Chau et al. 2006; Ove ARUP and Partners Hong Kong Ltd. 2006; Soga 2011), 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. However, 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 approach that must also include technical, economic, and social aspects (Holt et al. 2010; Steedman 2011). Carpenter et al. (2007) suggested that, for any decision-making framework, a combination of life cycle analysis and site- and material-speciﬁc factors can be more contextual than a singular metric. Jefferson et al. (2007) also pointed out that the use of one metric to evaluate the sustainability of a project may not always be sufﬁcient — a holistic sustainability assessment tool in geotechnical engineering upholding the four Es of engineering sustainability is required. Among the sustainability assessment tools that address the multi-dimensional character of sustainability, some are qualitative and represent the performance of a project on different sustainability-related sectors pictorially. One such qualitative indicator system, known as the sustainable geotechnical evaluation model, was developed by Jimenez (2004) and is used for comparing the sustainability of the different alternative materials used for slope stabilization. The system judges the sustainability of a geotechnical project based on the categories of social, economic, environmental, and natural resource use, and on other subcategories like water use, land use, and reusability of materials. Holt (2011) and Holt et al. (2009) developed GeoSPeAR, an indicator system for geotechnical construction, by modifying the sustainable project appraisal routine (SPeAR) developed by ARUP (2010) (Fig. 9). SPeAR uses a color-coded rose diagram to assess a project on the basis of four main criteria — social, economic, environmental, and natural resources — and 20 subcriteria. It consists of a circle, which is divided into sectors along the circumference based on the criteria and subcriteria mentioned earlier. Each sector corresponding to a subcriterion is further divided radially into seven color-coded segments. The performance of a project in a particular subcriterion is indicated by shading one of the segments with its respective colors. The closer the shaded segment is to the center of the diagram, the more sustainable the project is with respect to that particular subcriterion. GeoSPeAR replaced some of the master planning related indicators of SPeAR (e.g., accessibility to schools and recreational facilities, and availability of transportation facilities like pedestrian and bicycle facility and public transport infrastructure) with geotechnical-related indicators (e.g., responsible use of materials and resources, recycling and reuse of existing substructures, energy use, efﬁciency in design, and site investigation). GeoSPeAR also includes an optional provision for life cycle assessment (LCA) of a project to bring transparency to the sustainability indicators like carbon dioxide emissions, noise, and vibrations (Holt et al. 2010). Holt et al. (2009) provided a step-by-step procedure (Table 1) that should be followed in combination with GeoSPeAR, and suggested performing LCA to determine the impacts of a design choice on the resource base and the environment. Published by NRC Research Press Basu et al. 107 Table 1. Steps to be followed in assessing sustainability in geotechnical projects. Step Detail Pre-assessment Communication between all parts involved in the process Setting up boundaries for the assessment Data collection from the project for different indicators A baseline assessment using GeoSPeAR Identifying areas of sustainability concern Performing LCA to evaluate impact of different design options Reassessment of improvement for changes in design option Repetition of steps 5 and 6 to arrive at the expected level of improvement 1 2 3 4 5 6 7 The second category of multi-dimensional assessment frameworks consists of quantitative and life cycle based tools. Life cycle costing (LCC) has been used in pavement design for choosing the economically best option among different alternatives (Riegle and Zaniewski 2002; Praticò et al. 2011; Zhang et al. 2011) — this approach puts some emphasis on the environmental and social impacts by converting these impacts into monetary value. Zhang et al. (2008) used a combination of LCC and LCA to assess the sustainability of pavements. Pittenger (2011) developed a performance metric known as green airport pavement index (GAPI) for comparing the sustainability of alternative airport pavement treatments — GAPI combines the performance of an alternative pavement treatment in the categories of LCC, resource use, and project management by using relative weights to calculate the metric. Lee et al. (2010a) combined LCA and LCC to quantitatively assess the advantage of using recycled materials in pavements — their study showed that considerable savings in the categories of global warming potential, energy consumption, water consumption, and hazardous waste generation can be made when recycled materials are used in construction. Lee et al. (2010b) modiﬁed the framework proposed by Lee et al. (2010a) and introduced a LCA-based rating system known as building environmentally and economically sustainable transportation – infrastructure – highways (BE2ST in-highways). BE2ST in-highways (Fig. 10) is primarily applicable for projects where recycled materials are used. In this framework, the stakeholders’ consensus on choosing the impact categories and the targeted reduction in those categories is required at the start of the project. Points are assigned to projects based on how closely the target values are achieved — the target values are set with reference to the impact that would be caused if virgin materials were used in place of recycled materials. Torres and Gama (2006) developed the environmental sustainability index (ISA) for quantifying sustainability of underground mining and geotechnical works. The ISA considers impact in the categories of (i) materials, water, and energy use, (ii) geotechnical and water qualities, (iii) atmosphere quality, (iv) biodiversity and cultural heritage, and (v) waste and environmental impacts. Misra (2010) and Misra and Basu (2012) proposed a muticriteria-based quantitative framework for assessing the sustainability of geotechnical projects — the framework considers resource consumption, environmental impact, and socioeconomic beneﬁts of a project over its entire life span (Fig. 11). The use of resources is taken into account based on the embodied energy of the materials used; the impact of the process emissions is assessed using environmental impact assessment; and the socioeconomic impact of the project is assessed through a cost beneﬁt analysis. Three indicators are derived from the three aspects and are combined through weights to calculate the sustainability index for the different alternatives available for the project. The third approach to sustainability assessment is based on pointbased rating systems that provide a measure of sustainability of projects based on points scored in the different relevant categories. Jefferson et al. (2007) proposed a set of 76 generic indicators and 32 technology-speciﬁc indicators for ensuring the sustainability of ground improvement methods. The indicator system, known as environmental geotechnics indicators (EGIs), was used at construction sites for ground improvement projects and is based on a point score system — one for harmful to ﬁve for signiﬁcantly improved construction practice. The system was developed by borrowing concepts from the existing sustainability indicators like SPeAR and BREEAM (Jefferson et al. 2007) and by modifying the concepts to suit the particular aspects of ground improvement projects. The EGIs system is designed to cover the entire range of activities over the lifetime of a project but does not consider the economic or social aspects of sustainability. Laefer (2011) developed a scoring system to augment SPeAR for assessing the sustainability of foundation reuse projects. In transportation infrastructure, some sustainability rating systems have been developed in recent years that inﬂuence the research on alternative geomaterials. These include GreenLites (McVoy et al. 2010), I-LAST (Knuth and Fortmann 2010), Greenroads (Muench and Anderson 2009), and Ministry of Transportation Ontario (MTO) – green pavement rating system (Chan and Tighe 2010). These rating systems assign points to projects based on different categories, one of which is optimum use of natural resources. Thus, these rating systems provide an impetus to research in alternative sustainable geomaterials. Decision support systems are also in use in geotechnical asset management. The rockfall hazard rating system developed by the Oregon Department of Transportation (Pierson and Vickle 1993) and uniform condition index for assessing the performance of infrastructures (McKay et al. 1999) are examples of decision support systems that have been successfully used in transportation geotechnics. According to Bernhardt et al. (2003), most of the available asset management systems are for single asset systems, i.e., they do not consider the interconnected nature of the assets. As geotechnical assets are closely tied to other structures, the existing management systems may not be adequate for geostructures. Moreover, the existing systems do not consider life cycle costs and performance of the assets. Developing a performance-based asset management tool exclusively for geotechnical assets needs substantial effort, and such a tool is yet to be formulated (Bernhardt et al. 2003). Critical appraisal of existing literature It is often assumed that the use of recycled and alternative material contributes towards sustainable development. This may not be always true. For example, there is often a lack of sufﬁcient understanding and experience regarding the behavior of these alternative materials. Such lack of knowledge may lead to conservative estimation of material performance and greater consumption of materials, or to unanticipated failures, none of which supports the sustainability agenda. Moreover, the long-term performance of these materials is often not known, and degradation of the material properties may lead to failures. Further, some of the waste products used in construction, e.g., industrial wastes, may lead to contamination, which will adversely affect sustainable development. At the same time, a shift from traditional use of materials may adversely affect the local market, which in turn will affect the economy and lifestyle of the local community. Fleming et al. (2011) suggested that assessment of the risks associated with innovative use of materials and distribution of the risks among all the stakeholders are necessary to ensure that the approach to sustainability is not stiﬂed due to ﬁnancial reasons. Practices like innovative ground improvement techniques or reuse of geostructures should also be carefully assessed in terms of their effectiveness towards global sustainability. It is undeniable that reuse of foundations or use of solar energy in construction is a sustainable choice from material-use and environment Published by NRC Research Press 108 Can. Geotech. J. Vol. 52, 2015 Fig. 10. Design ﬂowchart of BE2ST in-highways. Fig. 11. Multi-criteria-based sustainability assessment framework. points of view. However, considering the entire project, these may sometimes have negligible beneﬁts, and the risks associated with the use of such alternatives (e.g., the risk of failure of existing old foundations due to lack of adequate information) may negate the use of such alternatives. Similarly, the use of geosynthetics may reduce the embodied energy of a geotechnical construction, but the performance of geosynthetics may not always be as good as traditional materials. For example, reinforced earth structures are more ﬂexible than steel reinforced earth structures and may be more prone to failure under sudden shocks like hurricane or bomb blast. For important structures, the use of steel reinforcement over geosynthetics may better serve the sustainability agenda, considering all the aspects of sustainability. Similarly, geosynthetics drains may not always perform better than a gravel drain. The use of underground space may fail to deliver on the social sustainability aspects, although performing well on resource use and economy, if such use does not satisfy the aesthetical and psychological makeup of the people using the underground facility. For example, creation of underground space for pedestrian walkways may cause security threats (e.g., these spaces may harbor burglars) in some countries, and such constructions may create more problems than solutions. At the same time, in some countries these walkways are used by homeless people and may lead to public nuisance. The important point here is that decisions on sustainability should not be based on “popular choices” but on rational judgments and thorough assessments considering the multi-dimensional and multi-disciplinary aspects of sustainability. It should be kept in Published by NRC Research Press Basu et al. mind that sustainable choices are situation and project speciﬁc, and one size may not ﬁt all. The earlier discussion is applicable to the sustainability assessment tool as well. Appropriate choice of a sustainability assessment framework depends on the scope and goal of a project. The assessment tools presented earlier may serve the profession well. However, none of these tools encompass all the aspects of sustainability from a multi-disciplinary point of view. For example, none of the presented assessment frameworks consider resilience. At the same time, the temporal dimension of changing sustainability objectives is not addressed in these tools. It is relevant to mention here that assessment frameworks like the Urban Futures method (Lombardi et al. 2012), applicable to urban development, and Envision sustainability rating system (ISI 2013), applicable to civil infrastructure, which have been developed in the recent past, have a much wider and comprehensive scope and are more holistic. It would be beneﬁcial to integrate these or similar holistic assessment frameworks to the available assessment frameworks in geotechnical engineering. Remarks on state of the art The civil engineering profession is witnessing a time of shifting paradigms at the backdrop of global climate change, economic downturn, population growth, and increased natural hazards. These factors have made governing bodies all over the world rethink the ways of day-to-day business, and endeavor toward sustainable development is an obvious outcome of such efforts. The geotechnical profession has also been motivated by the sustainability wave, which is particularly important because the profession lies at the interface of the natural and built environments, and can signiﬁcantly inﬂuence the economy, society, and environment. Recognition of sustainability as an important component of geotechnical engineering by the International Society of Soil Mechanics and Geotechnical Engineering (ISSMGE) and the GeoInstitute (GI) of the American Society of Civil Engineers (ASCE) through formation of sustainability-related committees and organization of sustainability-themed conferences (e.g., 18th International Conference on Soil Mechanics and Geotechnical Engineering (ICSMGE) 2013, Paris, France, and GeoCongress 2014, Atlanta, USA) is a testimony of the important and variegated roles geotechnical engineers play towards sustainable development of civil infrastructure. As the literature review shows, sustainability in geotechnical engineering is often driven by the common notions of environmental sustainability, and most projects and research studies focus on material reuse and recycling, energy efﬁciency, and minimization of wastes and emissions as the basis for sustainable development. Whilst it is important to put emphasis on “green” construction techniques, this alone will not achieve sustainable development. It is the holistic approach that balances the economic, social, and environmental needs and ensures robust engineering and resilience checks that will lead to sustainable development. In this regard, it is important to distinguish between constructions performed in a sustainable way and the sustainability of the ﬁnal product. Sustainable development can be achieved only through multi-dimensional assessment and decision-making considering all the pillars (four Es) of engineering sustainability. The current state of practice does not put much importance on the resilience of geostructures. However, for important geotechnical projects like dams and levee systems, resilience and adaptive management of the systems are as important for sustainability as the environmental, economic, and social aspects. As seen in the wake of Hurricane Katrina, the levee system in New Orleans designed as a rigid, fail-safe system was incapable of handling the storm surge and proved to be a major cause of the ensuing catastrophe. Therefore, particularly for geostructures that are related to critical infrastructures, reliability, resilience, and adaptive management should be incorporated in the design and assess- 109 ment of geotechnical systems. Iai (2011) identiﬁed three new trends in geotechnical design to incorporate sustainability: (i) geostructures are now designed for performance rather than for ease of construction; (ii) designs are now more responsive to site-speciﬁc requirements; and (iii) designs consider soil–structure interaction rather than just analysis of structural or foundation parts. Although the aforementioned trends are encouraging, the geotechnical profession is far from making sustainability as the all-encompassing goal because, like most other engineering professions, it is dominated by economic considerations. It is possible that a sustainable and resilient solution may result in greater initial cost, but sustainable solutions lead to less cost over the lifespan of the project or structure. Even if the cost is more, it is still important to go beyond ﬁnancial considerations and consider a holistic picture because, as ethical and responsible citizens and engineers, we are obliged to protect our environment, be sensitive to societal needs, and be fair to the needs and aspirations of future generations. At the same time, it is important to educate the public and engineers on sustainability. Within the geotechnical profession, there is still apathy and even skepticism towards sustainability among several professionals. Some consider sustainability to be an overused buzzword, and others believe that practices are already sustainable because most geostructures in the world adequately serve the design life. It has to be emphasized that sustainable engineering is not just about good engineering but smart engineering considering the future needs and constraints. Incentives from governing bodies would be helpful in encouraging sustainable practices. Such incentives should not only include direct ﬁnancial beneﬁts but also include legal securities in case of inadvertent and unanticipated failures as a consequence of sustainability efforts, sustainability education to communities, opening up communication channels among different stakeholders to understand and reach consensus on the demands and supplies, and encouragement to academia to perform research for making engineering processes, practices, and products sustainable and to educate the current and future generations about sustainability and its beneﬁts. Summary Incorporating sustainability in engineering requires an understanding of the deﬁnitions and ideological conﬂicts that characterize sustainability and of the approaches that can make engineering processes sustainable. Philosophically, sustainability is a global concept that requires equal distribution of all the resources of the planet among its inhabitants, minimization of the impacts of anthropogenic development, and equal opportunities for all species to grow and sustain themselves over generations. However, when sustainability concepts are incorporated in engineering, this global view is scaled down to an anthropocentric view with a focus on technological advancement, often without any knowledge of the complex interconnections between ecological processes and the built environment. Therefore, a gap exists between sustainability as a concept, and as it is used in engineering practice. There is a lack of consensus regarding what an ideal solution to sustainability problems in engineering can be or what the most suitable approach to solve such problems might be. Thus, there is a need for education, research, and effective communication regarding sustainability within the engineering profession. In practice, two approaches are generally used to incorporate sustainability in engineering: the business-as-usual approach and the systems engineering approach. The systems engineering approach can be further categorized into the system optimization approach and the three Es approach. The business-as-usual and system optimization approaches have a bias towards maximizing the ﬁnancial gain, while the three Es approach balances the economic, social, and environmental aspects of engineering processes. Sustainability in engineering should also include the reliability and Published by NRC Research Press 110 resilience aspects, and hence, instead of the three Es approach, a four Es approach, combining environment, economy, equity, and engineering design, has been suggested in this paper. Sustainability issues are particularly important for critical infrastructures that sustain the life line of human existence. Geostructures are essential components of all infrastructural systems, and failure in geostructures like slopes and dams often spells catastrophes to the natural and human environment surrounding it. These structures are resource intensive, and hence, a failure in these structures also translates into signiﬁcant economic loss for the community. Also, because geotechnical constructions take place at the initial stages of a project, incorporating sustainability in geotechnical construction can set a trend that may ﬁnally result in considerable ﬁnancial and environmental beneﬁts through the later stages of the project. Sustainability-related studies in geotechnology essentially belong to two categories: those that contribute to global sustainability through the use of alternative materials and innovative engineering and those that develop sustainability assessment frameworks. A critical review of the relevant research studies is provided. It is recommended that a holistic approach considering environmental, social, economic, reliability, and resilience aspects (the four Es) should be developed in geotechnical engineering for sustainable development of civil infrastructure and society. References Abdelaziz, S.L., Olgun, C.G., and Martin, J.R., II. 2011. Design and operational considerations of geothermal energy piles. In Proceedings of GeoFrontiers 2011, Dallas, Tex. [CD-ROM]. Abreu, D.G., Jefferson, I., Braithwaite, P.A., and Chapman, D.N. 2008. Why is sustainability important in geotechnical engineering? In Proceedings of GeoCongress 2008. Geotechnical Special Publication No. 178. pp. 821–828. doi:10. 1061/40971(310)102. Ahern, J.F. 2011. From fail-safe to safe-to-fail: sustainability and resilience in the new urban world. Landscape Architecture & Regional Planning Graduate Research and Creative Activity, Paper 8. Ali, M.M.Y., Arulrajah, A., Disfani, M.M., and Piratheepan, J. 2011. Suitability of using recycled glass-crushed rock blends for pavement subbase applications. In Proceedings of GeoFrontiers 2011, Dallas, Tex. pp. 1325–1334. [CD-ROM]. doi:10.1061/41165(397)136. Anderson, S., Chapman, T., and Fleming, J. 2006. Case history: the redevelopment of 13Fitzroy Street, London. In Proceedings of the International Conference on Reuse of Foundations for Urban Sites. Edited by A.P. Butcher, J.J.M. Powell, and H.D. Skinner. pp. 311–320. Andersson-Sköld, Y., Fallsvik, J., Hultén, C., Jonsson, A., Hjerpe, M., and Glaas, E. 2008. Climate change in Sweden – geotechnical and contaminated land consequences. In Proceedings of the 1st WSEAS International Conference on Environmental and Geological Science and Engineering, Malta, 11–13 September. pp. 52–57. Anochie-Boatang, J., and Tutumluer, E. 2011. Sustainable use of oil sands for geotechnical construction and road building. Journal of ASTM International, 9(2): 1–15. doi:10.1520/JAI103651. Arrow, K.J., Dasgupta, P., and Mäler, K.G. 2003. Evaluating projects and assessing sustainable development in imperfect economies. Environmental and Resource Economics, 26(4): 647–685. doi:10.1023/B:EARE.0000007353.78828.98. ARUP. 2010. Sustainable building designs strategy. Available from http:// www.arup.com/Services/Sustainable_Buildings_Design.aspx [accessed 29 October 2013]. Asadollahi, P., and Zeytinci, A. 2011. Sustainable development of infrastructures using underground spaces: role of academia. In Proceedings of the ASEE Middle Atlantic Regional Conference, Farmingdale State College, SUNY, 29–30 April. Barends, F.B.J. 2005. Associating with advancing insight: Terzaghi Oration 2005. In Proceedings of the 16th International Conference on Soil Mechanics and Geotechnical Engineering, Osaka, Japan, 12–16 September. pp. 217–248. Basu, D., Puppala, A.J., and Chittoori, B. 2013. Sustainability in geotechnical engineering – general report. In Proceedings of the 18th ICSMGE, Paris. pp. 3155–3162. Bernhardt, K.L.S., Loehr, J.E., and Huaco, D. 2003. Asset management framework for geotechnical infrastructure. Journal of Infrastructure Systems, ASCE, 9(3): 107–116. doi:10.1061/(ASCE)1076-0342(2003)9:3(107). Bocchini, P., Frangopol, D.M., Ummenhofer, T., and Zinke, T. 2014. Resilience and sustainability of the civil infrastructure: towards a uniﬁed approach. Journal of Infrastructure Systems, ASCE, 20(2). [Published online ahead of print.] doi:10.1061/(ASCE)IS.1943-555X.0000177. Bradshaw, S.L., Benson, C.H., Olenbush, E.H., and Melton, J.S. 2010. Using foundry sand in green infrastructure construction. In Proceedings of the Can. Geotech. J. Vol. 52, 2015 Green Streets and Highways 2010 Conference, ASCE, 2010: 280–298. doi:10. 1061/41148(389)24. Brandl, H. 2006. Energy foundations and other thermo-active ground structures. Géotechnique, 56(2): 81–122. doi:10.1680/geot.2006.56.2.81. Broch, E. 2006. Why did the hydropower industry go underground. In Sustainable underground concepts. Norwegian Tunnelling Society Publication 15. pp. 13–18. Brown, R.L. 1981. Building a sustainable society. W.W. Norton, New York. Brundtland, G.H. 1987. Our common future: report of the World Commission on environment and development. Oxford University Press, UK. Bruneau, M., Chang, S., Eguchi, R., Lee, G., O’Rourke, T., Reinhorn, A., Shinozuka, M., Tierney, K., Wallace, W., and von Winterfelt, D. 2003. A framework to quantitatively assess and enhance the seismic resilience of communities. Earthquake Spectra, 19(4): 733–752. doi:10.1193/1.1623497. Buchanan, R. 1992. Wicked problems in design thinking. Design Issues, VIII(2): 1–21. doi:10.2307/1511637. Butcher, A.P., Powell, J.J.M., and Skinner, H.D. (Editors). 2006a. Whole life cost and environment impact case studies. In Reuse of foundations for urban sites: a best practice handbook. IHS BRE Press, Berkshire, UK, pp. 116–119. Butcher, A.P., Powell, J.J.M., and Skinner, H.D. 2006b. Stonebridge Park – a demolition case study. In Proceedings of the International Conference on Reuse of Foundations for Urban Sites. Edited by A.P. Butcher, J.J.M. Powell, and H.D. Skinner. pp. 321–330. Carmody, J., and Sterling, R. 1985. Earth sheltered housing design. Van Nostrand Reinhold Company, New York. Carpenter, A.C., Gardner, K.H., Fopiano, J., Benson, C.H., and Edil, T.B. 2007. Life cycle based risk assessment of recycled materials in roadway construction. Waste Management, 27: 1458–1464. doi:10.1016/j.wasman.2007.03.007. Cascione, A., Williams, R.C., Gillen, S., Bentson, R., and Haugen, D. 2010. Utilization of post consumer recycled asphalt shingles and fractionated recycled asphalt pavement in hot mix asphalt. In Proceedings of the Green Streets and Highways 2010 Conference, ASCE, 2010. pp. 349–359. doi:10.1061/41148 (389)29. Chan, P., and Tighe, S. 2010. Quantifying pavement sustainability in economic and environmental perspective. Transportation Research Board 89th Annual Meeting, Washington. [DVD]. Chateauneuf, A. 2008. Principles of reliability-based design optimization. Structural design optimization considering uncertainties. Edited by Y. Tsompanakis, N.D. Lagaros, and M. Papadrakakis. Taylor and Francis. Chau, C., Soga, K., and Nicholson, D. 2006. Comparison of embodied energy of four different retaining wall systems. In Proceedings of the International Conference on Reuse of Foundations for Urban Sites. Edited by A.P. Butcher, J.J.M. Powell, and H.D. Skinner. pp. 277–286. Chau, C., Soga, K., Nicholson, D., O’Riordan, N., and Inui, T. 2008. Embodied energy as environmental impact indicator for basement wall construction. In Proceedings of Geo Congress 2008. Geotechnical Special Publication No. 178. pp. 867–874. doi:10.1061/40971(310)108. Chrismer, J.L., and Durham, S.A. 2010. High volume ﬂy ash concrete for highway pavements. In Proceedings of the Green Streets and Highways 2010 Conference, ASCE, 2010. pp. 390–400. doi:10.1061/41148(389)32. Ciro, G.A., and Alfaro, M.C. 2006. Adaptation strategies for road embankments on permafrost affected by climate warming. In Proceedings of the IEEE EIC Climate Change Technology Conference. pp. 1–10. doi:10.1109/EICCCC.2006. 277271. Clift, R., and Wright, L. 2000. Relationships between environmental impacts and added value along the supply chain. Technological Forecasting and Social Change, 65: 281–295. doi:10.1016/S0040-1625(99)00055-4. Curran, M.A. 1996. Environmental life cycle assessment. McGraw Hill, USA. Daly, H.E. 2005. Economics in a full world. Scientiﬁc American, September 2005, 293(3). Dam, T.V., and Taylor, P.C. 2011. Seven principles of sustainable concrete pavements. Concrete International, 33(11): 49–52. DeJong, J.T., Fritzges, M.B., and Nüsslein, K. 2006. Microbially induced cementation to control sand response to undrained shear. Journal of Geotechnical and Geoenvironmental Engineering, 132(11): 1381–1392. doi:10.1061/(ASCE) 1090-0241(2006)132:11(1381). Disfani, M.M., Arulrajah, A., Younus Ali, M.M., and Bo, M.W. 2011. Fine recycled glass: a sustainable alternative to natural aggregates. International Journal of Geotechnical Engineering, 5(3): 255–266. doi:10.3328/IJGE.2011.05.03.255266. Dixit, M.K., Fernández-Solis, J.L., Lavy, S., and Culp, C.H. 2010. Identiﬁcation of parameters for embodied energy measurement: a literature review. Energy and Buildings, 42: 1238–1247. doi:10.1016/j.enbuild.2010.02.016. Edwards, A.R. 2005. The sustainability revolution. New Society Publishers. Egan, D., and Slocombe, B.C. 2010. Demonstrating environmental beneﬁts of ground improvement. Proceedings of the Institution of Civil Engineers – Ground Improvement, 163(1): 63–69. doi:10.1680/grim.2010.163.1.63. EPA Victoria, Australia. 2009. Guidelines for environmental management: Use of biosolids as geotechnical ﬁll. Environment Protection Authority (EPA), Publication No. 1288, June 2009. Fauriel, S., and Laloui, L. 2011. A bio-hydro-mechanical model for propagation of biogrout in soils. In Proceedings of Geo-Frontiers 2011: Advances in Geotechnical Engineering. [CD-ROM]. pp. 4041–4048. doi:10.1061/41165(397)413. Published by NRC Research Press Basu et al. Fiksel, J. 2007. Sustainability and resilience: toward a systems approach. IEEE Engineering Management Review, 35(3): 5–12. doi:10.1109/EMR.2007.4296420. Firoozabadi, A., and Cheng, P. 2010. Prospects for subsurface CO2 sequestration. AlCHE Journal, 56(6): 1398–1405. doi:10.1002/aic.12287. Fleming, P.R., Frost, M.W., and Lambert, J.P. 2011. Geotechnical speciﬁcation for sustainable transport infrastructure. Available from https://dspace.lboro.ac. uk/dspace-jspui/handle/2134/3521 [accessed 27 December 2011]. Folke, C., Carpenter, S., Elmqvist, T., Gunderson, L., Holling, C.S., and Walker, B. 2002. Resilience and Sustainable development: building adaptive capacity in a world of transformations. Ambio, 31(5): 437–440. doi:10.1579/0044-7447-31. 5.437. Fragaszy, R.J., Santamarina, J.C., Amekudzi, A., Assimaki, D., Bachus, R., Burns, S.E., Cha, M., Cho, G.C., Cortes, D.D., et al. 2011. Sustainable development and energy geotechnology – potential roles for geotechnical engineering. KSCE Journal of Civil Engineering, 15(4): 611–622. doi:10.1007/s12205-011-0102-7. Gilbert, P.H., Ariaratnam, S.T., Connery, N.R., English, G., Felice, C.W., Hashash, Y., Hendrickson, C.T., Nelson, P.P., Sterling, R.L., et al. 2012. Underground engineering for sustainable urban development. Report of the Committee on Underground Geoengineering for Sustainable Development, National Research Council, The National Academic Press, Washington, D.C. Glendinning, S., Loveridge, F., Starr-Keddle, R.E., Bransby, M.F., and Hughes, P.N. 2009. Role of vegetation in sustainability of infrastructure slopes. In Proceedings of the Institution of the Civil Engineers, Engineering Sustainability, 162(2): 101–110. doi:10.1680/ensu.2009.162.2.101. Gradel, T. 1997. Industrial ecology: deﬁnition and implementation. In Industrial ecology and global change. Edited by R. Socolow, C. Andrews, F. Berkhout, and V. Thomas. pp. 23–41. Grov, E. 2006. Storage of hydrocarbon products in unlined rock caverns. Norwegian Tunnelling Society Publication 15. pp. 19–28. Harris, C. 2005. Climate change, mountain permafrost degradation and geotechnical hazard. In Global change and mountain regions. Edited by U.M. Huber. Springer, the Netherlands. Hempel, L.C. 2009. Conceptual and analytical challenges in building sustainable communities. In Towards sustainable communities. 2nd ed. Edited by D.A. Mazmanian and M.E. Kraft. The MIT Press. pp. 33–62. Henry, D., and Ramirez-Marquez, J.E. 2011. Generic metrics and quantitative approaches for system resilience as a function of time. Reliability Engineering & System Safety, 99(1): 114–122. doi:10.1016/j.ress.2011.09.002. Heerten, G. 2012. Reduction of climate-damaging gases in geotechnical engineering practice using geosynthetics. Geotextiles and Geomembranes, 30: 43–49. doi:10.1016/j.geotexmem.2011.01.006. Heerten, G., and Werth, K. 2010. Mitigation of ﬂooding by improved dams and dykes. In Proceedings of the International Sysmposium, Exhibition, and Short Course on Geotechnical and Geosynthetics Engineering: Challenges and Opportunities on Climate Change, Bangkok, Thailand. pp. 225–237. doi: 10.1680/grim.11.00011. Holling, C.S. 1996. Engineering resilience versus ecological resilience. In Engineering within ecological constraints. Edited by P. Schulze. National Academy Press, Washington, D.C. pp. 31–44. Holling, C.S. 2001. Understanding the complexity of economic, ecological, and social systems. Ecosystems, 4: 390–405. doi:10.1007/s10021-001-0101-5. Holt, D.G.A. 2011. Sustainable assessment for geotechnical projects. Ph.D. thesis, University of Birmingham, UK. Holt, D.G.A, Jefferson, I., Braithwaite, P.A., and Chapman, D.N. 2009. Embedding sustainability into geotechnics. Part A: Methodology. Proceedings of the Institution of Civil Engineers, 163(3): 127–135. doi:10.1680/ensu.2010.163.3.127. Holt, D.G.A., Jefferson, I., Braithwaite, P.A., and Chapman, D.N. 2010. Sustainable Geotechnical Design. In Proceedings of Geocongress 2010, Fla. [CD-ROM]. Hughes, P.N., Glendinning, S., Mendes, J., Parkin, G., Toll, D.G., Gallipoli, D., and Miller, P.E. 2009. Full-scale testing to assess climate effects on embankments. Proceedings of the Institution of the Civil Engineers, Engineering Sustainability, 162(ES2): 67–79. doi:10.1680/ensu.2009.162.2.67. Humphrey, D., and Blumenthal, M. 2010. The use of tire-derived aggregate in road construction applications. In Proceedings of the Green Streets and Highways 2010 Conference, ASCE, 2010. pp. 299–313. doi:10.1061/41148(389)25. Iai, S. (Editor). 2011. Towards global sustainability. In Geotechnics and earthquake geotechnics towards global sustainability. Springer. Inagaki, Y., Tsukamoto, M., Mori, H., Sasaki, T., Soga, K., Al Qabany, A., and Hata, T. 2011. The inﬂuence of injection conditions and soil types on soil improvement by microbial functions. In Proceedings of Geo-Frontiers 2011: Advances in Geotechnical Engineering. [CD-ROM]. pp. 4021–4030. doi:10.1061/ 41165(397)411. Indraratna, B., Rujikiatkamjorn, C., Kelly, R., and Buys, H. 2010. Sustainable soil improvement via vacuum preloading. Proceedings of the Institution of Civil Engineers – Ground Improvement, 163(1): 31–42. Inui, T., Chau, C., Soga, K., Nicholson, D., and O’Riordan, N. 2011. Embodied energy and gas emissions of retaining wall structures. Journal of Geotechnical and Geoenvironmental Engineering, 137(10): 958–967. doi:10.1061/(ASCE) GT.1943-5606.0000507. ISI. 2013. Envision sustainability rating system. Institute for Sustainable Infrastructure (ISI). Available from http://www.sustainableinfra...

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