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1
Sustainable and Resilient Ground Engineering
Sydney July 25 2012
Nick O’Riordan PhD PE CEngDirector/Principal Arup [email protected]
2
Sustainable and resilient Ground Engineering
•Context
•Embodied energy
•Capital carbon investment and operations & maintenance carbon
•Sustainability and resilience
•Repairable limit states
•Co-located infrastructure: making best use of invested carbon
3
MIT Sloan Management Review, January 23, 2012
Interviews with 4000 commercial sector managers in 113 countries
4
Urbanisation
Population of Rome Global variations
How much carbon do we emit?TotalPer capita
[Victoria 1230] [NSW 900]
Transition to Low Carbon EconomyNow a Legal Obligation in UK: Climate Change Act 2008
Reduction of carbon emissions on the 1990 levels- 26% by 2020- 80% by 2050
Carbon budgeting system – cap emissions over 5 year periods
Sustainable and resilient Ground Engineering
If not us, then who?
New EuroNorms: Sustainability of construction works
BS EN 15643-1:2010 Sustainability assessment of buildings: Part 1: General framework
BS EN 15643-2:2011 Assessment of buildings: Part 2: Framework for the assessment of environmental performance
BS EN 15978:2011 Assessment of environmental performance of buildings-Calculation method
None of these standards relate to geotechnical systems, and none define what is an acceptable Cap Carb investment payback period
Embodied Energy (EE)
is the total energy that can be attributed towards shaping a product to its current state
includes energy consumed in winning raw materials, processing and manufacturing products from them in a project-specific way
for Infrastructure works, EE enables different methods of construction/product delivery to be compared (e.g. sheet pile wall or concrete diaphragm/slurry wall or CDSM + soldier pile wall+permanent reinforced concrete box?)
enables fuel choices (and hence CO2 emission impact) to be made
enables construction plant utilisation/efficiency to be evaluated
Inventory of Carbon and Energy (ICE)University of Bath, UK
http://www.amee.com/blog/2011/08/01/inventory-of-carbon-and-energy-ice-2/
http://wiki.bath.ac.uk/display/ICE/Home+Page;jsessionid=DA1E0CED9CAFCE0A36AB78C5D5A704FE
BSRIA: UK Building Services Research and Information Association
https://www.bsria.co.uk/news/embodied-energy/
CO2 emission factors (kg/kWh generated in UK)Natural Gas 0.19
Diesel 0.25
LPG 0.21
Wind 0.00
CO2 emission intensities (kg/tonne)•Granite ballast at quarry gate 1.1
•Pulverised fuel ash 2.1
•Portland cement (non-renewable power source) 1000.0
1GJ = 0.06 to 0.1 tonne CO2
California is ahead of the other states…but like Australia (and maybe Britain) has chosen cap-and-trade rather than control consumption
First litigation challenge to AB 32 (the Global Warming Solutions Act) and the cap-and-trade program in Association of Irritated Residents, et al. v. California Air Resources Board, Case No. CPF-09-509562, ("Ass'n of Irritated Residents v. CARB "). Though environmental justice groups continue to object to cap-and-trade as the primary vehicle to reduce greenhouse ("GHG") emissions to 1990 levels by 2020, the California Supreme Court recently allowed California Air Resources Board's (“CARB") cap-and-trade implementation to move forward, and agency rule development continues.
National Law Review October 2011
California High Speed Rail: Life Cycle Assessment
After Chester & Horvath(2010) PKT=passenger-km travelled
CapitalCarb
Once it’s out there......
Original outcome: why build an expensive railway if there is marginal reduction in GHG emissions compared to car or airplane?
Corrected outcome: even a HSR train that is only 10% full is greener than driving, or a half-full airplane
....the damage is done
http://www.cahsrblog.com/2010/12/hsr-emissions-paper-was-wrong/
California High Speed Rail
However Chang & Kendall (2011)show around 8 years payback period
Is a CO2 payback period of 8 years acceptable, politically, socially, financially? Clearly 30 years is not!
‘construction and operation of the system would emit more GHG emissions than it would reduce for approximately the first 30 years’California Legislative Analysts Office, April 17, 2012. http://www.lao.ca.gov/analysis/2012/transportation/high-speed-rail-041712.aspx
New Motorway project payback
0
100,000
200,000
300,000
400,000
500,000
600,00020
1620
1720
1820
1920
2020
2120
2220
2320
2420
2520
2620
2720
2820
2920
3020
3120
3220
3320
3420
3520
3620
3720
3820
3920
40
CO
2(to
nnes
)
Year
Do Minimum: annual CO2 from use of motorway
Do Something: annual CO2 from use of motorway
Motorway project cumulative CO2
YearDo Minimum
(tonnes/day)
Do Something
(tonnes/day)
2016 359 3262031 419 349
Priority 3 (UK ICE Low Carbon Trajectory)
Like CapEx and OpEx but for carbon
Apply the concepts of CapCarb and OpCarb
CapCarb OpCarb
Materials
Transport
Installation
Maintenance
Usage
Whole Life Carbon
+
Detailed high speed rail comparison
•Piled slab, 11 km in total length, very soft ground approx 10 to 12m thick
•Chosen for ride quality stability/ predictability
•Embankment solution would have required either embankments 4.5m thick and vertical drains or thinner embankments with ground strengthening (DDSM, CMC etc)
•Was piled solution the best, from an energy efficiency standpoint?
Piled slab: 11 km (7 miles) length, Channel Tunnel Rail Link project, very soft soils: Thames Marshes, UK
Material Embodied Energy intensity (MJ/kg)for CTRL piled slab v embankment comparison
Ballast* and sub-ballast 1
Compacted fill 0.7
Virgin Steel 55
Recycled Steel 10
Concrete 2
Diesel 36
density of concrete 2240 kg/m3
density of steel 7840 Kg/m3
*Includes 100 km round trip from stockpile, but excludestransport from quarry
CTRL 310 piled slab - Assumption and boundaries (after Chau et al, 2012)
Boundaries - Linear site (11.3km) and time ( 2 years)- CTRL contract 310 excluding viaducts, bridges, electrifications- Just construction, exclude operation, maintenance and some preliminary
enablement works- Exclusion of manual labours, and associated travel- As-built records give duration and utilisation of plant- Ballast from stockpile (100 km round trip), quarry to stockpile excluded
Assembly of machineries NOT included- machine energy insignificant? Yet to be evaluated.- Reuse of machines, not just for one project.
Hypothetical embankment alternative- 4.5m thick, to give required dynamic behaviour on very soft ground- ground improvement to achieve 2 year construction- excludes bridge/viaduct transitions
CTRL Contract 310, high speed rail on piled slab: very soft soils
After Chau et al (2012), 4.5m total embankment thickness EE of ballast transport from quarry excluded
For new-build rail in the UK, ballast is a significant component in terms of EE and CO2
For new-build, structural solutions including slabtrack appear more efficient and ‘sustainable’
Can a ‘sustainable’ case be made for progressive replacement of ballasted track with slabtrack?
Slab track v ballasted track:Is received wisdom from the Shinkansen (the bullet train) truly correct?
‘Paved track is up to 1.3 times more expensive to install but significantly reduced maintenance results in pay-back in 9 years…’
IEEP (2006) for RMT Parliamentary Group Seminar ‘The Sustainable Case for Rail’
Slabtrack:
WCML Crewe -Kidsgrove
EE comparison for ballasted v slabtrack
•EE ballasted track maintenance=0.8 TJ/km
•Total EE of unoptimised slabtrack = 20 TJ/km
•Total EE of piled slab excluding ballast = 30TJ/km
•CO2 emissions for ballasted track maintenance = 50 tonnes/route km
•Total CO2 emissions for new slabtrack = 1,000 tonnes /km
•‘Payback period’ for new slabtrack versus ballasted track maintenance = 20 years
For new build railways in the UK, ballast is a significant component in terms of EE and CO2
Structural solutions including slabtrack appear more efficient and ‘sustainable’ than ballasted track
After Kaini et al, 2008)
Embodied Energy relationships (after Workman & Soga, 2004 and DTI, 2000)
UK masonry house = 414 GJ (100m2)
52 storey office, Australia = 2590 TJ (130000m2)
High Speed 1 Stratford>St Pancras UK
Twin bored tunnel, 11 km = 900 TJ (construction only)
1 GJ=277.8 kWh
Coal fired power= c.7500 kWh/tonne
LPG = 13722 kWh/tonne
Wood = c.3000 kWh/tonne
Tyres = 8888 kWh/tonne
Retaining walls: basic process & EE intensities
30
Carbon in Retaining Walls – steel verses concrete
Sheet Pile Propped Diaphragm 1Propped Diaphragm 2 Diaphragm(Cant)0
5
10
15
20
25
30
Site2 CO2 Emissions of Generic Basement Wall Designs Per Meter Run
CO2
Emiss
ions [
t-CO
2/m
]
SteelConcreteTransportInstallationProp
CO2 emissions /m run10m basement wall (recycled steel)
Sheet pile reuse
Concrete basement wall 400mm Sheet piles extracted
Propped sheet pile
AZ34
Propped diaphragm
800mm
Propped diaphragm 1000mm
Cantilever diaphragm 1500mm
Rented Props and sheet piles
AZ34
Embankments on soft clay:Speed v certainty
Very soft clays: design parameters difficult to determine without trials
Greater certainty by modifying soil behaviour/ load pathways and load magnitude
Embankments on soft ground: treatmentmethods
DDSM/
After O’Riordan & Seaman (1994)
Some Embodied Energy intensity values for soft ground engineering
Component EEI value*
Driven 300mm PC pile, 10m long, 2 tonne
6GJ/pile
DDSM @ 100 kg/m3 OPC from gas-fired power station energy source, 10m deep, 90 % coverage,
10GJ/ m2
Vertical, 100mm wide Prefabricated drain, 10m deep @1m c/c
1.5 MJ/ m2
Geogrid such as Tensar SS40 @ 0.53 kg/m2
40 MJ/ m2
11 tonne truck, average daily running speed =50 km/hr
2 MJ/km (pro-rata for lower daily running speeds)
* Excludes EE associated with transport of component to site
9m thick embankment, 2m settlement, with vertical drains @ 1m c/c
Embankment fill 12600 MJ/ m2
Vertical drains 1.5 MJ/ m2
Geogrid 40 MJ/ m2
If the 2m settlement, and the associated time for consolidation can be avoided using BASP piling, the comparable EE becomesEmbankment fill 9800 MJ/ m2300mm sq. driven piles @1.5m c/c 6000 MJ/ m2Tensar geogrid 40 MJ/ m2
TOTAL 15840
DDSM solution would be a further 5000 MJ/m2 above BASP
After O’Riordan (2006)
Embodied energy, CO2 footprinting and construction on soft ground
Current solutions are often driven by speed of construction and/or the need for certainty of outcome
Embodied energy calculations can enable the selected solution to be put into the wider project context, to become part of the overall environmental drivers for a given scheme
For example, a road bypass will have the effect of reducing local CO2 emissions by X tonnes/year, and the associated construction emissions are Y%.
Seven different alternative design concepts
Concord Community Reuse Plan
Alternative 1
Business-as-usual
Alternative 2
Maximum development
Alternative 5
Concentrated development
SATURN model IMPACT (average speed) CO2 emissions
• Established baseline CO2 for 2008
• Calculate future emissions
Sustainable transport analysis
Mobile source emissions added to stationary source emissions and normalized across the service population
ALT 1 Business-as-Usual
ALT 2 Maximum build-
out of site
ALT 5 Concentrated
, transit-oriented
development
Regional mobile emissions over No Project 95,208 145,766 52,446
Stationary emissions (TCO2e) 400,470 457,074 350,028
Total gross emissions (TCO2e) 495,678 602,840 402,474
Service population (residents + jobs) 39,200 59,600 45,800
GHG efficiency rate (TCO2e/person) 12.6 10.1 8.8
Concord Community Reuse Plan
24km long; dual 3-lane motorway •2 major interchanges; •29 structures
New motorway Carbon comparison
CO2 by construction element
Structures (including foundations)
Pavement
Earthworks
Operational CO2 (over 40 years) (tonnes)
Construction CO2 (tonnes)
Structures incl foundations
Pavement
Earthworks
Effect of vertical profile/alignment
Tunnel vs Bridge
“Long Tunnel” “Long Bridge”
Low gradient: low Op Carb High gradient: high Op Carb
Sustainability: ‘(an attribute of an activity or thing) that meets the needs of the present without compromising the ability of future generations to meet their own needs’, after Brundtland. So
this requires a look ahead towards higher/older population densities, developments in technology, and a desire to ensure that
chosen activities do not deplete resources significantly.
Resilience: the ability of a thing to return to its original shape and function. Something is not resilient if a lot of effort is required to return it to its original shape and function. So
earthquake code writers in California have chosen to prevent collapse of structures, for example, and admit that irreparable
damage may occur requiring demolition and replacement. This requires less investment (both carbon-based and money-based)
than a more resilient approach. There are exceptions, in particular, at Caltrans where the foundation system is capacity protected and the
superstructure has defined strain limits at both Safety Evaluation and Functional Evaluation levels. In the Caltrans case, careful balancing of cost
and selected return period is required. I would say that Caltrans’ approach is resilient, however it is ‘sustainable’ only if the carbon emission budget
is identified and optimized. Interestingly there is a trend towards ‘monopile’ foundations which are analytically simple to design but will tend to use
larger quantities of high greenhouse gas emitters like concrete and steel than an equivalent multiple pile group.
Sustainability and Resilience
Sendai airport, Miyagi prefecture, NE Japan
Tsunami from Tohoku earthquake March 11 2011
September 11 2011
June 3 2011
Design for resilience
http://blogs.sacbee.com/photos/2011/09/japan-marks-6-months-since-ear.html
Repairable Limit State
After Honjo (2010)After SEAOC (1995)
ULS (Life Safety) and SLS(Fully Functional) limit states rarely coincide
Increasingly often, the SLS is the governing load/resistance system, but this costs $$$ and CO2
Can we achieve savings by identifying a Repairable Limit State that is economically acceptable, and which provides adequate safety at ULS?
We have examples with highway and railway feedback and maintenance systems
We can do better!
Smarter analyses: piled foundations in karst
Coastal protection assessment, Monterey Bay CA
Comparison of probability of failure during design earthquake, and EE of selected solution
Soga & Chau (2006)
x10
Resilent foundations/capacity protection
Design (SEE) earthquake
- 5% probability of exceedance in 50 years from PSHA
(t = 975 yr)
Cable tower:
- Designed as ductile member
Cable design:
- Design for cable replacement
- Design for cable loss
Displacement control:
Cover damaged joints with steel plates
post-earthquake
Caltrans and monopiles
Carbon footprint of 4m dia. monopile = 20 No 1m dia.CIDH piles
Utility evaluation and resilience, urban centers/CBD
Transbay Transit Center, San Francisco
Electrical – Gas - Water Utility Plan
E EW G
E
Utility evaluation and resilience, urban centers/CBD
Utility evaluation and resilience, urban centers/CBD
3.0 s : first mode period of structure
Soil-Structure Interaction, Analysis Model
Bus Ramp TTC Superstructure
TTC Trainbox
Tiedowns
Soil Domain
Ground Motion
Wet Utility Flexible Joint
Multi-functional, co-located buried infrastructure
Natural temperature gradients at shallow depth
Pile test site at Monash Uni, Clayton, after Wang et al (2012)
Geothermal modelling and feedback systems
Analysis Hoop stress (MPa) Tensile Stress (MPa)
Winter Summer Winter Summer
‘Normal design’ in LC 10.4 10.4 2.0 2.0
0W extraction 11.4 12.6 3.1 3.4
30W extraction 12.9 13.5 3.1 3.5
Extracting 30W/m2Peak summer temp in tunnel is 36 degrees
Geothermal piles
Lambeth College thermal pile load test
Bourne-Webb et al (2009) Energy pile test at Lambeth College
LS-DYNA model
23m
Top 6m of pile has diameter 610mm
4m
Remainder of pile has diameter 550mm
5m
Model input dataLoad on pile. Graph shows equivalent load for a whole pile (the load in the model is a quarter of this value). The test pile was loaded to 1.8MN, unloaded, then loaded to 1.2MN. The load was held constant for the remainder of the test.
3. Reload to 1.2MN
2. Unload
1. Load to 1.8MN
Result – settlement vs timeSettlement prediction matches test well during the cooling phase, when the pile shrinks down into the ground.
During the heating phase, the model predicts that two thirds of the previous settlement will be recovered as the pile expands, but the test result shows that only one third is recovered.
If the top of the pile were prevented from expanding upwards, that would be consistent with the strain measurements that suggest an increase of applied load during the heating phase.
Model: /data3/rsturt/ENERGY_PILES/LAMBETH_JAN2012/RUN17_TDC/Lambeth_17_TDC.key
Cooling Heating
Result – pile strain distribution vs test
For compatibility with the published test results, thermal strains have been subtracted leaving only the mechanical (stress-inducing) strains.
During heating
Comment:Test result measurements appear to be influenced by head restraint. In the experiment, the load at the top of the pile was held constant
Model: /data3/rsturt/ENERGY_PILES/LAMBETH_JAN2012/RUN17_TDC/Lambeth_17_TDC.key
Sustainable ground engineering: ability to influence outcome during a project lifetime
After Pantelidou et al (2012)
Vehicle/structure characteristicsSupply chain
Define repairable limit stateMinimise waste
Summary
• Need to understand ‘business-as-usual’/Do Nothing in detail
• Need to consider Cap Carb and Op Carb
• For Transport projects involving high speed trains and/or freight movements, this means shallow gradients and more tunneling.
• What is an acceptable Cap Carb payback period if we Do Something?
• Relationship between resilience and sustainability: design for ‘repairability’?
• Co-located infrastructure: geothermal tunnels and piles
• Greater influence if involved early in the project lifetime
Sustainable and resilient Ground Engineering
If not us, then who?
If not now, then when?
Thank you
An uncertain future
http://www.americanlifelinesalliance.com
..it is the greatest happiness of the greatest number that is the measure of right and wrong
A Fragment on Government, Jeremy Bentham, 1776