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Craig Hiscock, Principal Fire Safety Engineer, Tunnels Team, Parsons Brinckerhoff delivered this presentation at the 2013 Australian Tunnelling conference. The two day conference is supported by the Australasian Tunnelling Society and brings together tunnelling leaders, engineers and industry experts to share best practice in tunnelling design, construction, safety and maintenance. The 2012 program focussed on updates from Australasia’s current and future projects, plus case studies from leading International projects - sharing best practice and lessons learnt from the forefront of the latest tunnelling projects. For more information about the event, please visit the conference website: http://www.informa.com.au/tunnellingconference
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Performance Based Fire Life Safety for Road Tunnels Craig Hiscock
22 November 2013
Reference Design Solution
Contractual prescriptive
design requirements
Stakeholder influences
Uniformity in tender
designs
Factors influencing recent design processes
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Examples of prescriptive design requirements
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• Twin tubes • Cross-passage spacing 120m • Smoke exhaust or management for large fires • Fire rated concrete to modified hydrocarbon fires • Fire resistant architectural panelling
Need for a tunnel identified
Austroad’s - Guide to road tunnels Part 2
AS 4825 – Tunnel fire safety
Tunnel FLS concept or reference design
AGRT Intended design development process
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• AGRT – 1 Section 10.3 states “The practice described in the forthcoming Australian Standard AS 4825 forms the basis of the requirements of the Austroads Guide to Tunnels”.
• AS 4825 recommends using risk, but, provides no risk acceptance criteria.
• AS 4825 provides process, but, allows process to be adapted to suit the circumstance.
• Neither Austroads or AS 4825 specifically cater for existing tunnel upgrades.
• AS 4825 read as a prescriptive document limits opportunities or innovation achieved by performance based design.
Limitations to current AGRT process
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• Quantitative or Qualitative? • Likelihood or frequency of events? • Consequence criteria – Life Safety, Asset, Operational? • Acceptance criteria – Fixed number, ALARP or Other? • Construction influences? • Operational influences? • Cost influences?
Risk and risk acceptance
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• New tunnel concept or existing tunnel upgrade
• Get the fire and ventilation engineers in early
• Consultatively quantify clients requirements
• Consultatively quantify stakeholder needs
• Document preliminary design (nuts and bolts)
• Demonstrate preliminary designs risk is ALARP
• Agree preliminary design is appropriate
• Proceed to tender or construction
Idealised design development process
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ALARP Assessment and Cost Benefit Analysis
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Example – Double stacked carriageway
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AS 4825 provides guidance on exit spacing and states: • Section 7.1 states - Spacing between exits within
tunnels are typically at a maximum of 120 m for road tunnels.
• Item (d) of the Preface states – “Specifically, this standard does not restrict innovative approaches or new technologies provided that the required performance can be demonstrated”.
• Section 5.9 Egress – provides performance requirements relative to occupant safety, therefore, provided appropriate egress outcomes are achieved, there may be opportunity to vary from the 120m spacing.
Example - Increasing cross-passage spacing
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Example - Fire Resistance and Suppression
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Example - Maximising smoke management opportunities
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Removal of smoke exhaust
Example - Smart lining solutions
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Example - Smart lining solutions
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AGRT Part 1: Section 3.3.6 provides guidance on the passage of DGV’s and states
• Whether to allow the free passage of dangerous goods vehicles operating within the law should be determined through a risk management approach and involve all relevant stakeholders (e.g. the tunnel owner and operator, fire and rescue authorities and regulators).
• One consideration is that diverting such vehicles off the major road system could transfer risk to locations that may not have facilities or ready access to deal with any emergency incident involving fire or spillage.
• In any case, the operational requirements for the tunnel will need to be designed to accommodate the possibility of an incident involving an illegal entry of a vehicle transporting dangerous goods.
• AS 4825 recommends that DGVs be assessed by a separate risk assessment process.
Example - Dangerous Goods Passage
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• Designs can sometimes be focussed on capital costs, therefore operational and ongoing cost may not be considered.
• Operational and ongoing cost can influence viability of a project.
• Innovative operational strategies can minimise running costs.
• Smart design solutions can minimise tunnel closures thereby improving level of service or availability of the tunnel.
• Clever use of equipment layouts and arrangements can minimise recovery time post incident.
Example - Whole of Life Costs
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Developed NZ specific supplement for NZ tunnels
Caters for both new and existing road tunnels
Focussed on minimising both physical provisions and Whole of Life costs
Utilises risk to determine appropriateness of outcomes
New Zealand’s approach to Austroads
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Austroads guide to road tunnels allows the provision of performance based design and innovation. To achieve better project outcomes, all parties need to give appropriate consideration the performance of a design including the whole of life and operational costs.
The final word
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Thank-you