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Arulrajah, A., Narsilio, G., Kodikara, J., & Orense, R. P. (2015). Key issues in
environmental geotechnics: Australia - New Zealand. Environmental
Geotechnics, 2(6), 326-330. doi:10.1680/envgeo.14.00005
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Environmental Geotechnics
Volume 2 Issue EG6
Key issues in environmental geotechnics:
Australia–New Zealand
Arulrajah, Narsilio, Kodikara and Orense
Environmental Geotechnics December 2015 Issue EG6
Pages 326–330 http://dx.doi.org/10.1680/envgeo.14.00005
Paper 14.00005
Received 16/02/2014; accepted 04/09/2014
Publisher online 06/10/2014
Keywords: energy/environment/recycling & reuse of materials
ICE Publishing: All rights reserved
Key issues in environmental
geotechnics: Australia–New
Zealand
1
2
Arul Arulrajah PhD, MEngSc, BSc, FIEAust, CPEng
Associate Professor, Swinburne University of Technology, Melbourne,
Australia
Guillermo Narsilio PhD, MScMath, MScCE, CEng
3
4
Jayantha Kodikara PhD, BSc, CPEng, FIEAust
Professor, Monash University, Melbourne, Australia
Rolando P. Orense Dr Eng, PE
Associate Professor, University of Auckland, Auckland, New Zealand
Senior Lecturer, The University of Melbourne, Melbourne, Australia
1
2
3
4
Because of climate change and increasing population in Australia–New Zealand, several key environmental geotechnics
issues are emerging. These key issues include the impact of climate change, depletion of natural resources, interest in
the use of recycled materials, advances in seeking new energy sources, disaster waste management as well as other
sustainability issues. Evaluation of climate change effects, adaptation technologies and interdisciplinary solutions for
geo-infrastructure and other key issues and challenges will be discussed in this paper.
Introduction
Environmental geotechnics issues are emerging in Australia and in
New Zealand because of climate change and increasing population
in the region. Geotechnical engineers in the region are increasingly
expected to meet the requirements for environmentally friendly
designs, constructions and innovations. End users in the region
increasingly expect the delivery of a project that can be certified
as clean and ‘green’, at the lowest additional cost possible. Climate
change in the region has resulted in the increased usage of sustainable
materials in geotechnical engineering as well as the usage of various
alternative clean energy sources such as geothermal and solar
energy. Moreover, the series of large-scale earthquakes in New
Zealand sparked the need for efficient disaster waste management
and recycling measures.
Climate change
It is widely accepted that the world’s climate is changing as evident
from anomalous warming of the earth’s atmosphere on average
(Figure 1). Since 1900, the average temperature appears to have
risen about 0·8°C and the rate of increase has also increased in
the later years, with an about 0·2°C rise in each decade. There is
substantial evidence to also suggest that the measured increase in
average temperatures is mainly due to the anthropogenic effects of
increase in greenhouse gas (GHG) emissions where carbon dioxide
is the predominant contributor. Using the anthropogenic effect as the
primary driver, the global warming predictions made into the future
indicate that temperatures could rise as much 2°C to 4°C by 2100
(Meehl et al., 2012). Along with such changes, significant variations
326
in long-term weather patterns have been forecasted around the globe.
For instance, in Australia, along with increased average temperatures,
overall reductions in precipitation but with varied rainfall patterns
with more intense rainfall events and severe droughts, sea level rises
and the likelihood of severe storms and bush fires have been predicted
(CSIRO, 2007). In New Zealand, on the other hand, in addition to
more marked seasonality in the projected rainfall and wind patterns,
other changes expected are decreased frost risk, increased frequency
of high temperatures, increased frequency of extreme daily rainfalls,
decreased seasonal snow cover and a possible increase in strong
winds (MFE, 2008). Such changes could have a severe impact on
the resilience of geo-infrastructure such as structural foundations,
road pavements, buried pipelines and other earthen structures like
dams and flood levees (State of Victoria, 2006). Natural slopes can
be affected by the intense rainfall, and sea level rise would have
adverse effects on the stability of coastal slopes. It follows then
that a geo-engineer has two major responsibilities to counter these
potential threats for the benefit of the wider community. The first is
to develop rational methodologies to evaluate climate change risks to
geo-infrastructure and to engineer adaptive technologies to maintain
structural resilience, where required. The second is to engineer
sustainable geo-related technologies to reduce GHG emissions, in
particular the carbon dioxide emissions.
Alternative energy
Since the industrial revolution, the rate of growth of the human
population and associated annual per capita energy consumption has
been exponential (Glassley, 2010). Mitigating the environmental
Environmental Geotechnics
Volume 2 Issue EG6
Key issues in environmental geotechnics:
Australia–New Zealand
Arulrajah, Narsilio, Kodikara and Orense
Offprint provided courtesy of www.icevirtuallibrary.com
Author copy for personal use, not for distribution
0·8
Temperature anomaly: °C
0·6
Annual mean
5-year running mean
0·4
0·2
0
−0·2
−0·4
−0·6
1870
1900
1930
1960
1990
2020
Year
Figure 1. Global temperature land–ocean index (data source:
NASA’s Goddard Institute for Space Studies (GISS))
impacts of an ever-growing human presence on the planet has
become inextricably linked with finding renewable energy sources
with low GHG emissions, particularly in Australia whose ‘carbon
footprint’ per capita is one of the largest in the world mainly
because of the use and export of coal. Table 1 summarises all energy
resources including fossil fuels, renewable and nuclear sources,
together with some of the issues where geotechnical expertise is
needed (Santamarina and Cho, 2011). There is no unique solution
to reduce GHG emissions, but a combination of measures is needed,
including the use of alternative, renewable and sustainable energy
sources. There are a number of renewable resources that possess
large amounts of energy, some easier to realise than others, and
some with a relatively advanced technology (e.g. solar and wind
energy). There are of course a number of strategies that can be used
with our current resources (e.g. geosequestration of carbon dioxide,
smart grid technologies, sustainable transport systems, energy
efficiency technologies).
Within the Australia–New Zealand (geotechnics) context,
geothermal energy is gaining momentum. Geothermal energy can
be used for the provision of heating, ventilation and air conditioning
(HVAC) to residential, commercial and industrial buildings as well
as for power generation (de Moel et al., 2010; Glassley, 2010;
Johnston et al., 2011) (see Figure 2). Power is generated on the
surface through turbines that are moved (directly or indirectly) by
the hot-enough fluid (~175°C) that returns from the ground. New
Non-renewable (fossil fuels)
Coal
Characterisation,
subsurface
response, mine
excavation and
instability, gas
recovery
Renewable
Gas
Petroleum
Hydrates,
low-T LNG
storage,
hydraulic
fracturing,
optimal
extraction
Fines and
clogging, sand
production,
borehole
instability, EOR,
heavy oil and
tar sand
Solar
Nuclear
Geothermal
Wind
Biofuels
Drilling, fracture
formation, heat
transfer, piles,
optimization
Off/onshore
foundations,
pseudodynamic
loading
Land and water
use, energy
efficiency, and
food impact
Engineered soils,
decommission,
leak detect and
repair, long-term
behaviour and
monitoring
Table 1. Energy resources and associated geotechnics involvement (modified from Santamarina and Cho, 2011)
327
Environmental Geotechnics
Volume 2 Issue EG6
Key issues in environmental geotechnics:
Australia–New Zealand
Arulrajah, Narsilio, Kodikara and Orense
Offprint provided courtesy of www.icevirtuallibrary.com
Author copy for personal use, not for distribution
(a)
(b)
Winter
Summer
Air temp typically
5−15˚C
Air temp typically
25–35˚C
Cold
GSHP
Hot
Hot
GSHP
Cold
Ground temp typically
18˚C
Enhanced
rock mass
Heat
Ground temp typically
18˚C
Heat
Figure 2. Schematic diagram views of geothermal energy systems:
(a) hot dry rock system for power generation and (b) direct
heating and cooling system where the primary (ground) circuit
is connected to the secondary (building) circuit using a GSHP in
winter and summer (typical temperature ranges for Melbourne,
Australia; note borehole not to scale)
Zealand has advanced considerably on commercial geothermal
power plants given its geological conditions (relatively shallow
magmatic activity), whereas Australia has embarked in advancing
hot dry rock technology by way of full-scale pilot power plants.
In the latter, ground temperatures needed for the generation of
electricity are found a few kilometres below ground surface (much
deeper than in New Zealand, but shallower and thus less expensive
to drill than other parts of the world); however, the permeability
of the rock to allow the injected fluid to heat up is so low that
the reservoir needs to be ‘enhanced’ or ‘engineered’ by way of
controlled fracturing. One of the most pressing environmental
issues arises from the induced microseismicity (from the fracturing)
and the geochemistry changes induced in the reservoir and the fluid.
Moreover, geothermal fluid extraction for electricity generation can
induce regional subsidence. In the Wairakei field in New Zealand,
for example, 1–2 m of regional subsidence, in addition to a number
of bowl-shaped regions with greater subsidence (including one that
reached 15 m), have been observed (Pender et al., 2013). Evaluation
and better understanding of such large-scale subsidence requires
comprehensive geotechnical investigation on undisturbed samples
from depths of up to 1000 m.
the energy required for heating and cooling by 66% compared
with electrical resistance heating and 42% compared with airsource heat pumps. The use of open-loop geothermal systems, with
discharge and interchange of fluids with the ground, poses more
environmental concerns than closed loop systems. In both cases,
the (environmental) effects of thermal plumes and efficiency are the
focus of ongoing research.
Although already well-established outside Australasia (Amatya et
al., 2012; Banks, 2008; Brandl, 2006; Preene and Powrie, 2009), the
other direct form of geothermal energy, for heating and cooling with
the use of a ground surface heat pump, is particularly growing in
the region. Energy use in buildings accounts for 26% of Australia’s
GHG emissions, and heating and cooling account for over half of
this energy use (CSIRO, 2010) and thus have a significant impact
on the required capacity of electrical infrastructure. In one of the
few comparative studies of its type, Stein and Meier (1997) report
that residential ground source heat pump (GSHP) systems reduce
328
In the realm of energy research and development, methane hydrates
are being considered as a potential fuel for the future. It is believed
that there is enough methane in the form of hydrates (methane
locked in ice) to supply energy for centuries. The Hikurangi
Margin east of New Zealand contains a >50 000-km2 large gas
hydrate province. First estimates suggest that the volume of gas
in concentrated hydrate deposits is in the order of 700 000 kg/m3
(Pecher and Henrys, 2003), which is more than 100 times New
Zealand’s annual gas consumption between 2005 and 2009.
Should even only a fraction of New Zealand’s gas hydrates be
economically recoverable, they could provide the main source of
natural gas for New Zealand for several decades (Pecher and GHR
Working Group, 2011). Dissociation (‘melting’) of hydrate can
generate large volumes of gas that may weaken the seafloor and
trigger submarine landslides and tsunamis. Moreover, extraction of
the gas hydrates involves complex physical events (e.g. changes
in the soil structure and thermal conductivity, pore fluid and gas
migration and other complicated phenomena), which could cause
consolidation and shear deformation of the ground due to changes
in the effective stress and decrease in soil particle strength (Hyodo
et al., 2013). Thus, geotechnical engineers need to investigate the
geomechanical properties of methane hydrate-bearing sediments
not only for safe and economic exploitation but to understand the
risk associated with seafloor instability.
Environmental Geotechnics
Volume 2 Issue EG6
Key issues in environmental geotechnics:
Australia–New Zealand
Arulrajah, Narsilio, Kodikara and Orense
Offprint provided courtesy of www.icevirtuallibrary.com
Author copy for personal use, not for distribution
Recycled waste materials
The urgent need to lower the carbon footprint of geostructures in
the region is increasingly being explored because of the growing
depletion of natural resources and disposal cost (Arulrajah et
al., 2013a; Hoyos et al., 2011). The requirement to lower carbon
footprints in the design and construction of various civil engineering
projects is an increasing requirement for clients in many projects.
The growing interest in lowering carbon footprints has in recent
years led to end users, design consultants and contractors pursuing
new technologies that embrace design, materials and construction
methods that are environmentally friendly.
Construction and demolition (C&D) materials are the excess or
waste materials associated with the construction and demolition of
buildings and structures, including concrete, brick and reclaimed
asphalt (Sustainability Victoria, 2010). In Australia, approximately
8·7 million tons of demolition concrete, 1·3 million tons of
demolition brick, 3·3 million tons of waste excavation rock, 1·0
million tons of waste glass and 1·2 million tons of reclaimed
asphalt pavement are stockpiled annually (Arulrajah et al., 2013a).
Following the 2010–2011 Canterbury (New Zealand) earthquake
sequence, Christchurch City was significantly damaged, with
widespread liquefaction in the eastern suburbs of the city. Ongoing
rebuilding efforts indicate that an estimated 4 million tons of
building debris will be generated from demolition and building
repair works and up to 4 million tons from horizontal infrastructure
(i.e. roads, water, sewer and stormwater pipes) repairs. In addition
to the large amounts of C&D materials, an excess of 510 000 tons
of liquefied sand and silt was generated following the earthquakes
(CERA, 2012).
Reuse options for C&D or commercial and industrial waste in
geotechnical engineering applications are increasingly being sought
in the region as their reuse provides substantial benefits in terms of
increased sustainability and reduced environmental impact. The usage
of C&D materials in pavement applications is a sustainable option
that has been explored in recent years globally and is rapidly gaining
momentum in acceptability in the region (Arulrajah et al., 2013a;
Landris, 2007; Poon and Chan, 2006; Puppala et al., 2011; Sivakumar
et al., 2004; Tam and Tam, 2007; Wartman et al., 2004). Ultimately,
only through further research can a framework for using new and
different categories of waste materials in geotechnical engineering
applications be established. Several researchers have investigated the
usage of various recycled C&D materials in laboratory applications
(Azam and Cameron, 2013), and furthermore, road pavements and
footpaths are increasingly being constructed in the region using
recycled C&D materials (Arulrajah et al., 2013b). Figure 3 shows a
road pavement base constructed using recycled glass blends.
Depending on their nature and severity, disasters such as
earthquakes, bushfires and floods can create large volumes of debris
and waste, the majority of which ends up as C&D wastes. As the
waste volumes from a single event can be the equivalent of many
times the annual waste generation rate of the affected community
and can overwhelm existing solid waste management facilities
Figure 3. Laying of pavement base layer composed of glass
blends (Arulrajah et al., 2013b)
and personnel, management of disaster waste is very important.
Following the Christchurch earthquakes, a new, low-engineered
disposal site was set up in Burwood to dispose of all presorted
and unrecyclable demolition wastes (Brown, 2012). Inert wastes
(concrete, asphalt, brick, natural fill) were taken to Lyttelton Port
and used for land reclamation. Ground improvement techniques
that use in situ soil are being tested as liquefaction countermeasure
to try to find a use for the 510 000 tons of grey sand that has been
collected. Similarly, road filler made from cement mixed with silt
from liquefied sites has also been trialled.
Other forms of recycled materials that are rapidly generating research
interest in the region include various forms of commercial wastes,
industrial wastes, municipal solid wastes and organic wastes.
Conclusions
Various key issues associated with environmental geotechnics,
such as climate change, disaster wastes and recycling materials,
have emerged and posed as major challenges to geo-engineers
in Australasia. These issues have stimulated advanced research
and application of adaptation technologies in an environmentally
sustainable manner as well as the development of interdisciplinary
solutions that require shared knowledge among the different basic
and applied sciences and technologies. Thus, geo-professionals
in the region need refined and/or new sets of skills in theoretical
modelling and experimentation capabilities and to extend their
classical soil and rock mechanics background while interacting
with researchers in other disciplines to come up with safe and
sustainable design, construction, operation and maintenance of
geo-infrastructures.
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Environmental Geotechnics
Volume 2 Issue EG6
Key issues in environmental geotechnics:
Australia–New Zealand
Arulrajah, Narsilio, Kodikara and Orense
Offprint provided courtesy of www.icevirtuallibrary.com
Author copy for personal use, not for distribution
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