sustainability issues for underground space in …...issue advantages or mitigatio ns disadvantages...

Ray Sterling, Ph.D., P.E.Professor Emer i tus , Lou is iana Tech Univers i tyTan Swan Beng Endowe d Professor, Nanyang Technolog ica l Univers i ty

Sustainability and Resiliency Issues for Urban Underground Space

Tan Swan Beng Lecture, July 9, 2013, Nanyang Technological University2Tan Swan Beng Lecture, July 9, 2013, Nanyang Technological University

Introduction

� Underground space uses include a wide variety of systems critical to societal functioning and urban livability

� Effective underground space use also is a form of land creation

� It is important to assess the sustainability and resiliency implications of an expanded use of underground space

3Tan Swan Beng Lecture, July 9, 2013, Nanyang Technological University

Why Use Underground Space?

� Three main categories of rationale� Location: We want to build a facility in a particular place but

we don’t want to or cannot build it on the surface

� Isolation: We can use the physical attributes of the ground to hide or improve the isolation of certain types of facilities

� Topography and crossings: We can use the freedom from topographic constraints and the ability to tunnel under barriers such as rivers and mountains.


Why is Underground Space Use Important for Singapore?

� Singapore has an increasing population and growing economy but a very limited land area

� At the same time, Singapore is working hard to improve “quality of life” and environmental conditions

� Underground space use is one of the few options that offers significant growth potential for industrial purposes and infrastructure provision with minimal environmental impact.


Making Sensible Choices

� Underground space usually not the first choice for a facility “all other things being equal”

� Underground space use is not a “goal”

� It is often a response to alternatives that have a worse impact on quality of life

� It may eventually be one of only a few viable solutions for continued development

� To make proper choices both land value and environmental protection must be properly included in facility and infrastructure decisions


Build High Rise Structures

� Provides high density with access to daylight

� Intensifies need for infrastructure

� Much of this infrastructure must be provided underground

� Can be out of scale with historic areas


Land Reclamation

� Needs large quantities of fill material

� Extent limited by international treaties and deeper water

� Underground construction can contribute to the fill required


Floating Structures

� Need sheltered offshore location

� In many locations may interfere with recreational use of coastline

� Again, underground construction can help contribute to needed fill for protective reefs, etc.


Underwater Space

� Not too shallow, not too deep

� Need protection from anchors, sinking objects, etc.

� Corrosion issues

� Repair / renewal issues


Offshore Structural Development

� Create underwater space and new “land” using structures rather than fill

� Essentially create underwater space and new land at the same time

� Water easily moved aside


Infill Development / Create a New Ground Level

� Fill between and/or cover over existing land uses

� Create new ground surface

� Need large development or redevelopment

� Create “underground space” aboveground


Sustainability


Pillars of Sustainability


� Over what time scale is sustainability to be considered? Any consumption of non-renewable resources will eventually lead to exhaustion of those supplies at feasible costs.

� How can the current world population growth be reconciled with global sustainability?

Serious and Difficult Questions (1)


� How can regional imbalances in needs and resource availability be solved?

� Is it feasible to support current living patterns if regions become critically short of resources or if environmental changes increase the magnitude and frequency of natural hazards?

� Will people need to move to safer or more resource rich areas? Will this be feasible politically?

� The rapid urbanization of the world’s population requires that urban communities must provide a viable mode of living for the foreseeable future.

Serious and Difficult Questions (2)


Past Societal Collapses

� Extent and reversibility of environmental damage - fragility/resiliency of the local environment)

� Climate variations (drought, volcanic eruptions, etc.) and their impact on food supplies, etc.

� Presence of hostile neighbors� Decreased support from friendly

neighbors that interrupts essential trading � Whether and/or how a society recognizes

and responds to the developing crisis.

Issue Advantages or mitigations Disadvantages or limitations

Compactness

� New facilities/services with low surface impact

� Land use efficiency and promotes compactness while maintaining livability

� 3-dimensional planning freedom

� Local geology must be accommodated

� Poor knowledge of geology and existing underground structures

� Irreversibility considerations� Support, span and access

limitations

Isolation

� Protects from climate, storms, fire, earthquake

� Protects from noise, vibration, explosion, fallout, industrial accident

� Provides high security

� Flood protection required� Psychological concerns� Fire safety and personal safety

concerns

Preservation

� Low visual impact� Preserves natural landscape, ecology � Isolates hazardous materials and

processes� Low material degradation

� Skilful design required for best effect

� Environmental degradation from underground construction and use itself

Life cycle cost

� Land cost savings� Potential sale of excavated materials � Savings in specialized features� Savings in maintenance, insurance

and energy use for some facilities� High longevity of facilities

� Often high initial construction cost� Higher degree of cost uncertainty � Often high embodied energy � Limited access may affect operating

cost 18Tan Swan Beng Lecture, July 9, 2013, Nanyang Technological University

Surface Ecology Impact


Renewable vs Non-renewable Attributes

After Bobylev 2009


� Saving natural resources, including land, water, and biodiversity

� Reducing air pollution (mainly in the transport sector) and unnecessary visual intrusion

� Creating opportunities for less energy use and waste generation (compact city)

� Creating structures less impacted by earthquakes and many other catastrophic events and resilient utility and transportation networks

� Enhancing of overall landscape and environmental quality

� Underground infrastructure allows a reduction of land area covered by manmade structures.

� Compact areas that maintain high living standards can impact energy consumption and climate change

Underground Contributions to Sustainability


� Deep foundation choices for buildings

� Use of horizontal tiebacks for temporary/permanent support of foundation walls

� Choice of tunnel geometry and construction method

� Use of geothermal heat exchange systems

� Utility layout decisions / HDD impacts / utilidors

� Impact of underground structures on the geoenvironment

Examples of Design Choices Affecting Sustainability


Impact of Foundation Type on Underground Space Use


Sustainable Utility Provision

Wall Street 1917


Key Impacts for Singapore Sustainability

� Major increase in industrial/commercial spaces possible

� Multiple layers possible� Basement spaces

� Rock cavern spaces with multiple internal floors

� Multiple layers of rock cavern spaces possible

� Retains surface environment

� Provides aggregate and fill to support other construction and space creation activities

� Allows unobtrusive provision of key infrastructure services


Resiliency


Increasing Complexity of Infrastructure Relationships

� Aging physical systems

� Larger interconnected networks

� Poorly understood interdependencies

� Loss of redundancy for “economy”

After Rinaldi et al. 2001

Interdependencies for 6 Sectors of infrastructure


Metrics for Resiliency

� Describes the extent of loss of performance during the recovery period

Performance response function

Nelson and Sterling 2012


Electric Power Performance for Hurricane Katrina (Entergy New Orleans data)


Interdependence of Social Networks, Mobility and Utilities

� Restoring physical networks only is not enough


Challenges for Broad Application of Resilience

� Engineers and social scientists are not thinking in concert about representation of resilience

� Planners and land use professionals are noticeably absent from discussions of resilience

� Poor linkage between currently defined outcomes/metrics and standards or policy incentives

� The assessment of resilience is not yet standardized, and approaches and models have not been validated


Effects of Decision-making on Resilience

After McDaniels, Chang et al, forthcoming in Global Environmental Change

Response time

Excesscapacity, robustness

Support for function and delivers from outside the system

Influence of Adaptive Response Mgmt

Influence of Mgmt before an event

Event magnitude w/r to system capacity

Specific Resiliency Issues for Underground Space Use

32

Hurricane Sandy, New York Oct. 2012

Type of Event Advantages or mitigations Disadvantages or limitations

Earthquake

Ground motions reduce rapidly below surface

Fault displacements must be accommodated

Structures move with the soil Instability in weak materials or poor configurations

Hurricane, Tornado Wind loadings have minimal impact on fully buried structures

Damage to shallow utilities from toppling of surface structures such as trees and power lines

Flood, Tsunami Ground provides protection from surge and debris flow

Extensive restoration time and cost if the structure is flooded

External fire, blast Ground provides effective protection

Entrances and exposed surfaces are weaknesses

External radiation, chemical/biological exposure

Ground provides additional protection

Appropriate ventilation system protections required

Internal fire, blast Limited extent of damage with appropriate compartmentalization

Confined space increases internal damage and personnel risk

Internal radiation, chemical/biological releases

Limited extent of damage with appropriate compartmentalization

Confined space increases internal damage and personnel risk 34Tan Swan Beng Lecture, July 9, 2013, Nanyang Technological University

Protection, Security and Resiliency

� Seismic amplitudes reduce rapidly below surface

� Structures well protected from external events

34

Earthquake Date Magnitude Impact on Subway

Mexico City 1985 8.1 No damage to tunnels. Some power disruption. Patrons evacuated safely

Loma Prieta (SF) 1989 6.9 No damage to tunnels. Subway served as lifeline structure.

Northridge 1994 6.7 No damage

Kobe, Japan 1995 7.2 No damage to tunnels, damage to station and sewer pipes. Attributed to 1962 design with moderate seismic provision

Taipei 2002 6.8 No damage

Chile 2010 8.8 Running next day. Some damage at entrance to station

(From ITA WG20 Report)


Flooding a Key Concern for Underground Structures

� Protection of entrances against flooding is a key

� Underground structures well protected against forces generated by tsunamis, floods and debris flow

Flooded Taoranting Subway Station in Beijing, June 23, 2011. [Photo/Xinhua]


From Dr. Tetsuya Hanamura

2011 Earthquake / Tsunami Effect on Infrastructure in Sendai

� Only minor damage in below ground portions of subway and rail network

� Most aboveground gas facilities near seaside were destroyed

� Underground LNG tanks safe� Low damage in higher pressure

gas pipelines, more in low pressure lines

� Aboveground power plants destroyed

� Underground electric transmission lines only damaged at 14 locations

� Minor damage in water piping network


External Fire / Blast

� Types of Risk� Bush fires

� Industrial explosions

� Terrorist actions

� Nuclear explosion

� Mitigation� Protection of openings

� Keep out burning debris

� Withstand flying projectiles

� Deflection of blast outside the structure

� Blast resistant openings


External Radiation, Chemical/Biological Exposure

� Enclosed space beneficial

� Provide ventilation with filtration and, if necessary, blast protection

Filtration

Blast valves


Internal Fires Underground


Major Tunnel Fires


Elements of Fire Safety in Tunnels and Underground Spaces

� Control of hazardous material and cargos

� Fire Detection

� Ventilation

� Communication Systems / Traffic Control

� Sprinklers/Stand Pipes (Hydrants)/Water Supply / Portable Fire Extinguishers

� Tunnel Drainage

� Egress / areas of refuge

� Emergency Response


Internal Chemical / Biological Releases

� Enclosed space not beneficial for those inside

� Mitigation� Prevention

� Ventilation

� Egress

� CompartmentalizationExample: In five coordinated attacks, sarin was released on several lines of the Tokyo Metrokilling thirteen people, severely injuring fifty and causing temporary vision problems for nearly a thousand others.


Assessment of Damage to Urban Buried Infrastructure in the Aftermath of Hurricanes Katrina and Rita


Overview

� Katrina made landfall on August 29, 2005. Hurricane left relatively little damage but levee failure caused catastrophic damage

� EPA preliminary estimates to repair decimated water and sewer systems: $3 - $10 billion.

� Natural gas distribution system, power and telecommunication – an additional $1-2 billion.

� Costs of restoring municipal services alone dwarf costs of rebuilding lower Manhattan following 9/11.


Damage to Buried Infrastructure – Shallow Buried Infrastructure Systems

� Falling trees / tree root system � Common failure mode in mature neighborhoods � Damage to shallow utilities:

� Water� Low pressure gas� Power� Telecommunication

� Clean-up activities� Debris clearing operations � Off-road heavy equipment � Damage to hydrants

� Emergency response issues� Personnel could not report for duty� Landmarks obliterated� Electrical systems for pumps flooded


Damage to Buried Infrastructure – Severing of House Connections to Buried Utilities

� Shifting of above ground structures

� Even if structure experiences only partial buoyancy – rigid connections are severely damaged


Damage to Pipe Networks

� Potable water� Drop of pressure in pipes coupled with 3 m of external hydrostatic pressure can

result in the infiltration of contaminated water to the water distribution system

� Potential damage to liner rehabilitation systems

� Sanitary and Storm Sewer Lines� Differential settlement � Loss of bedding support � Off-road heavy equipment

� Natural gas� Salt water contamination / corrosion

of valves and meters� Acceleration corrosion of pipes� Mostly low pressure network affected


Short-term vs Long-term Impacts

� Short-term� Loss of potable water supply / water-borne illness

potential� Exfiltration of wastewater from damaged system /

pollution� Down time / business losses / population loss � Costly temporary services

� Long-term� Accelerated deterioration of buried pipes and

manholes� Infiltration causes loss of pipe and road bedding� Collapse of road surfaces� Infiltration can overwhelm wastewater plants in

wet weather � Increased failure of water mains


2012 Hurricane Sandy Impacts on New York

� Many similar issues as for Hurricane Katrina� Various metro and road tunnels flooded

� Storm surge� Heavy rainfall� Old metro system with many openings to surface

� Trees and overhead power lines downed� Electrical substations flooded� Power to lower Manhattan restored in about 4 days� 80% of metro service restored in about 5 days� Long-term repairs needed in many areas


Summary and Conclusions

� Underground space use can be a strong contributor to a livable and sustainable future for Singapore

� Underground space use offers a number of advantages in terms of urban resiliency but key issues such as flooding potential and fire/life safety must be considered carefully

� The potential large increase in the use of underground facilities for various purposes provides a significant incentive for advanced research� Better understand planning and societal implications� Improve technologies to lower costs and improve functionality� Provide greater synergy among various development alternatives for

maintaining a spacious and livable Singapore

MANY THANKS TO THE TAN SWAN BENGFOUNDATION SUPPORT FOR THE

OPPORTUNITY TO VISIT NTU AND COLLABORATE IN ADDRESSING THESE

IMPORTANT QUESTIONS

Questions and Discussion

sustainability issues for underground space in …...issue advantages or mitigatio ns disadvantages...

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