Tunnel Systems

systems

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ISSUE NO. 78 DECEMBER 2014

A technical journal by Parsons Brinckerhoff employees and colleagues http://www.pbworld.com/news/publications.aspx

PARSONS BRINCKERHOFF

Tunnel Systems

Fire Table andofLife Contents Safety

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Tunnel Systems INTRODUCTION

CLIMATE CHANGE AND RESILIENCY

Global Perspectives on Tunnel Systems John Munro, Kate Hunt, Steven Lai, Argun Bagis..............3

Railway Cooling Challenges Mark Gilbey .........................................................................60

FIRE AND LIFE SAFETY

Dynamo – Enhancing Tunnel Ventilation Modelling Jolyon Thompson ................................................................63

Subway Tunnel Cross-Passage Spacing: A Performance-Based Approach William D. Kennedy, Justin M. Edenbaum, Mia Kang, Kirk G. Rummel....................................................................10 A Note on Fixed Fire Fighting Systems in Road Tunnels Anna Xiaohua Wang, Norman Rhodes ...........................13 Fixed Fire Fighting Systems in Road Tunnels – System Integration Matt Bilson, Sal Marsico ....................................................16 Fire-Life Safety and System Integration: The Functional Mode Table Matt Bilson, Andrew Gouge...............................................19

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VENTILATION SYSTEMS Using Quantified Risk Assessment to Inform Ventilation System Responses Kate Hunt ............................................................................23 A Risk-Based Approach to Jet Fan Optimisation Anthony Ridley ....................................................................26 Cost-Effective Ventilation System for a Light Rail Transit Project Silas Li, Andrew Louie ........................................................30 Meeting the Challenges of Smoke Duct Fan Selection for Australian Road Tunnels Chris Chen ...........................................................................34 Analysis Considering the Conversion of an Existing Road Tunnel Transverse Ventilation System to Transit Use Jesse Harder, Andrew Louie, Vamsidhar Palaparthy, Silas Li...................................................................................37 Long Road Tunnels and Portal Emission Control Argun Bagis, Duncan Saunsbury ......................................41 Merging Emergency Ventilation System Sound Power and Pressure Drop Calculations Michael MacNiven ..............................................................44 Cost-Effective Power Supply Scheme for Tunnel Booster Fans in Long Tunnels CC Cheung, Steven Lai ......................................................48 Air Purification System for a Road Tunnel Project Cathy Kam, Chris Ma, Steven Lai .....................................51

PRESSURE TRANSIENT Elimination of Portal Flares Kenneth J. Harris, Bobby J. Melvin, Steve Gleaton ..........52 Comparison of 3-D and 1-D CFD Simulation Approach for Aerodynamic Effects in a HSR Tunnel System Dicken KH Wu, Rambo RB Ye ............................................55

ASSET MANAGEMENT AND PROGRAM SUPPORT Asset Management Database for the Brooklyn Battery Tunnel Ferdinand Portuguez, Debra Moolin..................................67

COMMUNICATIONS / POWER AND ELECTRICAL SYSTEMS SCADA System Security for Two UK Road Tunnels Peter Massheder ................................................................71 CCTV Design for a US Road Tunnel Ryan Williams .....................................................................73 How Alternating Current Interacts with Direct Current in the Shatin to Central Link Traction Systems in Hong Kong – A Quantitative Approach Sam Pang ............................................................................76

CONSTRUCTION AND REHABILITATION Tunnel Inspection Basics for Mechanical and Electrical Systems James Stevens, Mark VanDeRee.......................................81 Tunnel Sump Construction Savings Through Drainage System Design Modification Kevin Stewart ......................................................................86

LIGHTING The Modernization of Tunnel Lighting and Controls: Technology, Challenges, and Cost of Implementing a Tunnel LED Lighting System Christopher J. Leone, Jonathan T. Weaver, Kimberly Molloy ..................................................................89

SES AND MODELING Evaluating Freeze Protection Needs with CFD Raylene C. Moreno .............................................................92 Computational Modeling as an Alternative to FullScale Testing for Tunnel Fixed Fire Fighting Systems Kenneth J. Harris ................................................................96 Latest Enhancements to the Subway Environment Simulation (SES) Program Andrew Louie, Tom O'Dwyer, Silas Li ............................. 100 Use of Building Information Modelling (BIM) on Road Tunnels and Metro Projects YF Pin, R. Ashok Kumar, Steven Lai ............................... 102

Call for Articles .............................................................. 104

Introduction: Global Perspectives on Tunnel Systems

Advances in tunnel systems have evolved to account for a changing world, and Parsons Brinckerhoff’s response has been to ensure that we are both anticipating and responding to these changes and challenges as they occur and that we continue to provide innovative and robust solutions to our clients. Responding to the challenges of climate change, and the resiliency needed to adapt to a rapidly changing climate, or providing sustainable energy and environmental solutions require advances in existing tunnel system technologies and new technologies. Examples of this could be the design of a sustainable LED lighting solution for the Queens Midtown Tunnel in New York or using groundwater to cool the rising temperatures in the London Underground tunnels (see Mark Gilbey’s article in this issue). Parsons Brinckerhoff remains at the forefront of the provision of tunnel safety system solutions and their continued improvement as technology evolves. Our understanding of fire behavior and development in tunnels has increased considerably as a result of testing 1

programs such as the Memorial Tunnel Fire tests1 in West Virginia, led by Parsons Brinckerhoff, and more recently the Runehammer fire test program in Europe. This has allowed us to develop more focused strategies that address individual tunnel fire sizes and specific risks. For example, Parsons Brinckerhoff designed a tunnel fire suppression system for the Doyle Drive tunnel project in California. The recently opened Airport Link tunnel in Australia has emergency exits with builtin voice messages to guide users to safety in the event of a fire incident. Although systems technology has advanced significantly over the years, we must keep asking: What will the needs be for future tunnel owners, operators, and users and how do we develop our tunnel systems to respond to those needs? The imperative to provide resiliency in our designs and to ensure that our designs are also energy efficient and sustainable are what drives our solutions. Parsons Brinckerhoff has become a charter member of the Institute for Sustainable Infrastructure to affirm our commitment to the underlying principles of sustainable infrastructure, as well as the specific, evolving practices that characterize sustainable solutions. Our tunnel systems designers are trained in sustainability assessment. We also need to keep researching and innovating. Our 2014 William Barclay Parsons Fellowship winner, Anna Wang of our tunnel systems team in New York, is developing a model to predict the interaction of fixed fire fighting systems on tunnel fires. The outcome of this work will be used to achieve more efficient designs leading to considerable cost savings for our clients. (See Anna Wang and Norman Rhodes’ article in this issue.) Finally, we need to recognize that smart or connected road and rail vehicles are a rapidly developing part of our

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For decades, Parsons Brinckerhoff has been at the forefront of providing innovative tunnel systems solutions to our clients. In 1973 at the First International Symposium on Aerodynamics and Ventilation of Vehicle Tunnels in Canterbury England, attended by representatives from 26 different countries, a paper was presented on the Subway Environmental Simulation (SES) program codeveloped by the late William D. Kennedy. That paper led directly to a contract for the design of an extension to the Hong Kong Metro and, out of that project, Parsons Brinckerhoff’s Hong Kong office was established. Over 40 years later in 2015, Dr. Norman Rhodes of Parsons Brinckerhoff will chair the 2015 16th International Symposium on Aerodynamics, Ventilation, & Fire in Tunnels to be held in Seattle.

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See “Pioneering New Technology: PB’s Innovation in M&E Analysis and Design,” (Network #34, Spring 1996) for three articles on the Memorial Tunnel Fire Ventilation Test Program, at the time the most comprehensive full-scale fire ventilation testing undertaken.

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NETWORK present and future. Parsons Brinckerhoff is involved in a program to evaluate connected vehicle technology. The potential for connected vehicles to interact with tunnel systems is limitless. Imagine a tunnel ventilation system that automatically regulates its airflow based on the number and type of vehicles travelling through the tunnel or a deluge system putting out a vehicle fire without waiting for a tunnel operator to respond to the emergency.

Tunneling Overview in the United States by John Munro, New York, NY, US, +1-212-465-5588, [email protected]

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Standards such as NFPA 130, ‘Standard for Fixed Guideway Transit and Passenger Rail Systems,’2 or NFPA 502, ‘Standard for Road Tunnels, Bridges, and Other Limited Access Highways,’ have been a cornerstone guiding the design of tunnel systems for the last few decades. In many countries, these have been used as the de-facto international standards shaping the design of tunnel solutions globally. In the United States, Parsons Brinckerhoff has been central in shaping the direction of both NFPA 130 and NFPA 502 through active committee participation and chairmanship. Perhaps the most significant development in recent years is the change from purely prescriptive standards to standards that allow performance-based approaches. For example, NFPA 130 states: ”Nothing in this standard is intended to prevent or discourage the use of new methods, materials, or devices, provided that sufficient technical data are submitted to the authority having jurisdiction (AHJ) to demonstrate that the new method, material, or device is equivalent or superior to the requirements of this standard with respect to fire performance and life safety.” The change from prescriptive to performance-based designs has led to a situation where designers can exercise a greater level of flexibility and innovation in providing solutions for our clients. For example, previous standards prescribed a fan inlet temperature that had to be met without regard to the actual temperature that a fan inlet may experience in a fire. The current standards require that designers analyze the actual fan inlet temperatures that would be experienced for the type of fire that could be realized in relation to the specific rolling stock for that system. Another example is

described in “Subway Tunnel Cross-Passage Spacing: A Performance-Based Approach,” by Kennedy, Edenbaum, et al, which shows that the spacing of cross-passages, the width of walkways, and the width of cross-passages all have an effect on the simulated evacuation time from a train stopped in a tunnel. Performance-based design challenges designers to more accurately define inputs and parameters, and thus create more accurate models. As with any engineering design, the more accurately you can define and analyze the situation, the less conservative the design and, hence, more value is provided to our clients. An example of Parsons Brinckerhoff adding value for our clients by more accurately defining design inputs is in the area of analyzing design fires. Historically, design fires were prescribed, often conservatively, based on limited information at the time. The advancement of analysis tools, such as computational fluid dynamics (CFD), coupled with better research data, allows us to much more accurately define the design fire which is a major criterion in tunnel system design. CFD and risk analysis were used on recent projects to determine the fire curves for the projects, ultimately leading to a cost-effective design. (See “Cost-Effective Ventilation System for a Light Rail Transit Project,” by Silas Li and Andrew Louie.) As alternative procurement and delivery methods, such as design-build, become more frequent in the US, performance-based tunnel systems design can play a central role in providing value. Design-build projects are essentially outcome-based and innovation plays a central role in defining their success. The flexibility of performancebased design not only allows but encourages innovation, making it an ideal design methodology that is suited to design-build projects. On recent projects, we have been using the latest fire modeling and heat transfer techniques to refine tunnel structure thickness requirements due to fire effects. Reducing structural thickness can reduce construction cost and delivery schedules. In addition to the design and construction of new tunnels, such as the recently opened Port of Miami Tunnel, there is an increasing focus in the US on aging infrastructure. MAP-21 (the Moving Ahead for Progress in the 21st Century Act of 2012) includes funding for continued improvement to tunnel conditions that are essential to protect the safety of the traveling public. Parsons Brinckerhoff has continually developed and refined our

NFPA 130 (2014) and NFPA 502 (2014), National Fire Protection Association, www.nfpa.org

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High speed rail projects frequently involve long tunnels and long distances between stations. Parsons Brinckerhoff can draw on global and local experience to provide solutions for unique challenges such as analyzing the pressure waves associated with high speed trains (see article by Wu and Ye) and providing cost-effective tunnel ventilation and fire and life safety strategies to accommodate the extended egress distances of long tunnels.

Tunnelling Overview in the United Kingdom, Europe, and the Middle East by Kate Hunt, Godalming, UK, +44 (0)1483 528966, [email protected] The UK’s tunnelling market has seen substantial and rapid growth in recent times, with more tunnels predicted in the near future for the rail, metro, road, and utilities networks. The 1990s saw a number of significant new tunnelling projects including the opening of the Limehouse Link tunnel (road – 1993), the landmark Channel Tunnel (rail – 1994), the Jubilee Line Extension (metro - 1999) and, more recently, the High Speed 1 tunnels (high speed rail – 2007), the Lower Lea Valley utilities tunnel (2012), and the long-awaited Hindhead Tunnel (road - 2011). The Docklands Light Railway added new tunnels as part of the Lewisham (rail – 1999) and the Woolwich Arsenal extension (rail – 2009). The Crossrail project, a new commuter line railway running East/West below Central London, is also in construction. In addition, significant investment has been made to refurbish, upgrade, and improve a number of key road tunnels around the UK including the Hatfield and Bell Common tunnels (on London’s M25 orbital motorway), the Mersey tunnels (Liverpool), Tyne Tunnel (Tyneside), Saltash Tunnel (in the South-West), and refurbishment is ongoing or planned for the North Wales Coast Road tunnels and the Brynglas Motorway tunnel (South Wales). 3

Alongside this infrastructure investment, Transport for London’s metro operator, London Underground, has been investing heavily in replacing the fleet and increasing the service levels on all their lines. Parsons Brinckerhoff has a long and ongoing history of assisting London Underground in these works. Looking to the future, we are working towards the construction phase of High Speed 2, linking London with Birmingham and on to the North East and Scotland; phase 1 of the route alone features a dozen new high speed rail tunnels ranging in length from just 500 metres (1640 feet) to an impressive 13 kilometres (8 miles). Other tunnel-related rail projects in the planning stages include the Northern line extension to Battersea, the Bakerloo line southern extension, and Crossrail Phase 2. In addition, further tunnelled crossings of the River Thames are being considered, along with a number of urban road tunnels on the periphery of London. However, the investment in the UK’s tunnels market was small in comparison to the enterprising projects undertaken in Scandanavia, Istanbul, the Middle East, and Israel. A new fixed link between the countries of Sweden and Denmark was opened in 2000: the Øresundsbron linked the metropolitan areas of Copenhagen in Denmark and Malmö in Sweden via a combined rail and road link consisting of the 8 kilometre long (5 mile) Øresund bridge and 4 kilometre (2.4 mile) Drogden tunnel. Similarly, the Marmaray Crossing in Istanbul (opened in 2013) successfully negotiated the Bosphorus Strait - one of the busiest shipping lanes in the world - to connect the European and Asian parts of the old city via a 1.5 kilometre (.9 mile) immersed tube tunnel – the world’s deepest at 60 metres (196 feet) below sea level.3 Meanwhile, in the Middle East, more than $279 billion worth of projects were being planned or underway in 2012. A high proportion of these are in the transport sector, including metro schemes for Abu Dhabi, Cairo, Doha, Jeddah, Kuwait, Riyadh, and Tehran. Similarly, designs for the proposed metro in Israel’s Tel Aviv urban district continue to be developed, with the construction phase drawing nearer. At the same time, plans for a high speed rail line from Tel Aviv to Jerusalem are being developed. Many of our past and current projects involve technical innovations, or cutting edge techniques to address clients’ unique challenges. Whether we are providing strategic advice to operators (see the “Railway Cooling Challenges” article by Mark Gilbey in this issue), leading discussions

For 18 articles on many aspects of this multidisciplinary project including 5 articles on tunnel mechanical and electrical systems, see “Linking Two Continents: The Marmaray Project,” Network #65, June 2007, pp 1-58.

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techniques, including using the latest inspection and asset management technologies, to efficiently assess existing tunnel infrastructure (see articles by Stevens and VanDeRee; and by Portuguez and Moolin). Following the assessment, our performance-based methodologies are used to develop innovative upgrades that provide a level of safety equivalent to code-compliant solutions and that minimize or eliminate interruptions to tunnel operations.

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NETWORK with the UK’s Climate Projections group (UKCP), developing a new toolset such as DYNAMO to address a developing market (see Dr. Jolyon Thompson’s article in this issue, a version of which won the 2014 Parsons Brinckerhoff Emerging Professionals Technical Paper competition), developing sustainable designs through the use of innovative cooling techniques such as groundwater cooling or embedded liners, using the latest risk-based techniques to optimise designs and operations (see articles in this issue by Kate Hunt and Anthony Ridley), or introducing world-class high speed rail to the UK, our team of engineers is at the forefront of innovation. Parsons Brinckerhoff continues to retain its high profile in tunnel systems capability through many of the major projects being undertaken. Parsons Brinckerhoff’s in-depth knowledge and internationally renowned global team is able to deliver technical excellence to clients across all geographies and all sectors. As we engage with WSP, the challenge in the Europe, Middle East, and North Africa regions is to enhance our service offering across a broader range of sectors, to embrace the many exciting opportunities available, and to continue to provide our clients with the technical excellence they rightly expect of Parsons Brinckerhoff.

Tunneling Overview in Asia DECEMBER 2014 http://www.pbworld.com/news/publications.aspx

by Steven Lai, Hong Kong/Singapore, +852-2963-7625 / +65-6589-3661, [email protected]

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Parsons Brinckerhoff has a rich history of working on major tunnel projects and designing innovative solutions for tunnel systems in Asia. Some of these designs, concepts, and challenges are presented below. Closed systems and platform screen doors. In the 1970s, Parsons Brinckerhoff introduced an energy efficient closed system for the first metro in Hong Kong thereby providing a comfortable air-conditioned station environment for passengers. Then in late 1970s, with the availability of a more advanced signaling system for accurate train stopping positions, Parsons Brinckerhoff introduced the platform screen door (PSD) system for the first metro in Singapore and has continued to be involved in this design for other metro systems in the region (e.g., Japan, India, Mainland China, Taiwan, Thailand, and Vietnam). A PSD system can provide a more comfortable and less dusty environment inside the station, for example, 25 degrees C instead of 28 degrees C (77 degrees F

instead of 82 degrees F), a reduction of air velocity at the platform edge and staircases, and a lower noise level. Better land use and increased carrying capacity. Parsons Brinckerhoff provided engineering design support in the conversion of an elevated metro line to an underground metro line in Taiwan, resulting in better land use and a better interchange (transfer) arrangement with other metro lines. Parsons Brinckerhoff is also assisting various clients in increasing the capacity of existing metro lines through extending the catchment area, modification of rolling stock, and reducing headway of the trains. Subway Environment Simulation (SES), computational fluid dynamics (CFD) modeling, and evacuation models have been used to study the impact of these methods on the environmental control systems (ECS) and the fire and life safety systems in stations and tunnels and to assist clients in establishing cost-effective design schemes. Fire engineering approach. Since the mid 1990s, a performance-based fire engineering approach has been widely used to analyse the heat release rate from a train, the tenable environment along the evacuation path, etc. Parsons Brinckerhoff has adopted this approach for projects in Hong Kong, Taiwan, and Singapore, and was recognized with an award for innovation for the design of a station with an atrium in Shanghai. Parsons Brinckerhoff has also assisted metro companies in the integration of individual operations control centers (OCC) for existing lines and new lines in the region. Pressure transient from high speed trains. The high speed trains in Taiwan and Mainland China travel at 300kph (186mph) or even greater speeds. The pressure transient created by high speed trains can create issues for the passengers inside the trains, stations, and areas around ventilation shafts and tunnel portals. Parsons Brinckerhoff has developed various mitigation schemes which have been used to resolve the pressure transient issues in the Hong Kong Airport Express Railway, Taiwan High Speed Railway, West Rail in Hong Kong, several metro systems in mainland China, and Express Railway Link in Hong Kong. (See article by Dicken Wu and Rambo Ye in this issue.) Parsons Brinckerhoff’s work on road tunnels includes: • design of the 2km (1.2 mile) Cross Harbour Tunnel in Hong Kong in which a transverse ventilation system was used; • design of a longitudinal ventilation systems for road tunnels in Singapore with the use of the critical velocity concept;

New challenges in tunnel systems. Nowadays, exceptionally long tunnels with large cross-sectional areas and/or multi-purpose tunnels create new challenges to engineers. Parsons Brinckerhoff has participated in the following design of tunnel systems for several special tunnel projects in China: • the 18km long (11 mile) Zhong Nam Shan Tunnel with very long ventilation shafts, more than 500 meter (1640 feet); • the 6km long (3.7 mile) Chongming road tunnel which links Shanghai to the out-lying Chongming Island and has an upper deck for vehicular traffic and a lower for the metro line; • the 2km long (1.2 mile) Fuxing East Road Tunnel in Shanghai which also has an upper deck and a lower deck both of which are used for vehicular traffic; and • the Macau Sai Van Bridge which has an upper deck used for vehicular traffic and an enclosed lower deck used for light rail operation (normal condition) and vehicular tunnel operation (during typhoon conditions). Value engineering and cost effective design. Parsons Brinckerhoff has developed various value engineering schemes and creative approaches to achieve cost effective design for our clients and provide a better environment for the people. These schemes include: • the use of combined ventilation shafts instead of individual ventilation shafts to reduce the constraint on the station planning and the size of aboveground structures (Suzhou metro); • the use of a centralized chilled water system to reduce the overall spatial requirement and result in a more energy-saving system (Tsuen Wan Line in Hong Kong); • the use of higher voltage to supply the power for tun-

nel ventilation equipment in long tunnels to reduce the cable cost and overall spatial requirement, as described in an article by CC Cheung and Steven Lai in this issue (Airport Express Line in Hong Kong, Cheung Ching Tunnel in Hong Kong); • sharing of tunnel ventilation fans for different lines (Taiwan Nankong Extension); • use of Saccardo nozzles to replace numerous jet fans (West Rail in Hong Kong, KPE in Singapore); • use of tunnel cooling systems for long tunnels to reduce the number of ventilation shaft structures (Tsuen Wan Line in Hong Kong); and • the use of water mist systems to cool down long vehicular tunnels (Chongming road tunnel in Shanghai). Apart from the above, with the use of CFD modelling, Parsons Brinckerhoff has designed and developed costeffective ventilation systems for various cable tunnels in Hong Kong, Singapore, and Mainland China. Building Information Modelling. To increase productivity and provide a better visualization of complicated engineering solutions to stakeholders, Parsons Brinckerhoff is the first company in Hong Kong to use building information modelling (BIM) for the tunnel systems of a road tunnel project. Parsons Brinckerhoff is also the first company in Singapore to use BIM for designing the mechanical and electrical (M&E) systems in a metro project, and has also used BIM for a cable tunnel project in Singapore. (See article by YF Pin, R. Ashok Kumar, and Steven Lai in this issue.)

Tunnelling Outlook in Australia and New Zealand by Argun Bagis, Sydney, AUS, 61-2-9272 5435, [email protected] Australia’s population is projected to grow significantly by 2050, with Sydney, Melbourne, and Brisbane identified as cities where the majority of this growth will take place. Accordingly, the development of road and rail infrastructure has been at the forefront of the Australian government’s priorities and has resulted in the construction of a number of strategic road tunnels, and the safeguarding of rail corridors, primarily on the eastern coast of Australia. There are a significant number of tunnelling projects in the works for the latter half of this decade. Funding has already been approved for most of the nine new tunnels

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• minimizing the tunnel construction cost of the 3.9km long (2.4 mile) Tate’s Cairn Tunnel in Hong Kong with the use of construction shafts as permanent ventilation adits, which also resulted in early completion of this design-build project; • design of the 2km long (1.2 mile) Western Harbour Crossing in Hong Kong with optimized mechanical and electrical (M&E) services and ventilation ducts. This reduced the overall immersed tube tunnel cross-section and resulted in construction cost savings; and • design of an Air Purification System (APS) for the Central and Wanchai Bypass project in Hong Kong in order to produce cleaner air at the tunnel portals and the ventilation buildings. This system has been applied to various road tunnels in order to achieve a better environment. (See article by Cathy Kam, Chris Ma, and Steven Lai in this issue.)

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NETWORK 8.0 $ Billion

Forecast

Brisbane Underground (QLD)

Forrestfield Airport Rail Link (WA) 6.0

M4 East (NSW) Toowoomba Range Second Crossing (QLD)

Lane Cove Tunnel (NSW)

Legacy Way (QLD)

2.0

East-West Link Eastern Section (VIC) CityLink Western (VIC) M1 to M2 Link (NSW)

Cross City Tunnel (NSW) 03 05 Year ended June

East-West Link Western Section (VIC)

M5 East (NSW)

North-South Bypass Tunnel (QLD) East Link (VIC)

0.0

East-West Link (QLD)

North West Rail Link (NSW)

Airport Link (QLD)

4.0

M4 South (NSW)

Melbourne Rail Link (VIC)

07

09

11

13

15

17

19

21

23

Source: BIS Shrapnel, ABS Data

Figure 1 – Major road and rail projects with tunnel components (value of work done)

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currently being planned along the east coast of Australia, with the west coast expecting some movement as well with the planning of an extension to the existing metro system.

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In addition, the Australian government is focused on shifting the transportation of freight from road to diesel rail. This raises the need to upgrade existing rail infrastructure as well as to develop new rail routes to relieve the already congested east coast rail network. Rail projects linking the city of Brisbane with Melbourne over a new inland rail path, the extension of this rail path to the Port of Brisbane, and the Maldon to Dombarton rail link in New South Wales are initiatives that have been brought to the forefront of infrastructure spending. Tunnel ventilation and fire & life safety are key aspects in the successful delivery of these projects. Figure 1 provides both a summary and a forecast for the tunnelling sector in Australia, from 2003 through to 2023. As is evident from the graph, the outlook for tunnel projects from 2014 onward is looking very positive, and there will be a strong need for specialist engineering services, such as in tunnel ventilation. Brisbane, QLD in particular became (and continues to be) a major centre for tunnelling construction in Australia, with the construction of the M7 Clem Jones Tunnel (Clem 7), Airport Link and Northern Busway, and Legacy Way (still under construction) road tunnels. Parsons Brinckerhoff has been involved in the detailed design work on many unidirectional traffic tunnels. Chris Chen’s article on “Meeting the Challenges of Smoke Duct Fan Selec-

tion for Australian Road Tunnels” describes the unique fan duty requirements for this type of tunnel ventilation system, employing a combined longitudinal and distributed smoke extraction ventilation (smoke duct) system for fire emergencies. In New Zealand, the Waterview Connection for Auckland’s Western Ring Route is the largest road project ever undertaken in the country, including a 2.5-km long twin-tube tunnel with three lanes in each tunnel. Parsons Brinckerhoff is a member of the Well-Connected Alliance which is both delivering the project, and operating and maintaining the facility for 10 years after the opening. Kevin Stewart’s article on “Tunnel Sump Construction Savings through Drainage System Design Modification” describes how this DBOM project structure gave all parties an interest in costeffective design for both construction and maintenance. Parsons Brinckerhoff has diversified into non-traditional road and rail tunnel services. The re-development of existing rail stations, provision of post construction services to tunnel operators, and even mine ventilation have been markets where Parsons Brinckerhoff has delivered successful outcomes. Other examples of technical challenges include: • The planning and design of longer tunnels which is gaining momentum in Australia. A reduction in vehicle emissions, traffic fleet composition, and recent innovations in ventilation plant design have enabled the design of tunnel lengths to be almost double that of existing Australian tunnels, with fewer intermediate tunnel ventila-

nels. Climate projections beyond 2030 and 2050 are now commonly used for the design of tunnel ventilation systems. Overall, the future demand for tunnel ventilation and tunnel systems in Australia looks strong, with funding for major road and rail tunnel projects already confirmed. The challenge remains to fully utilise Parsons Brinckerhoff’s capability outside of the traditional concept phase by taking on leading roles in the detailed design, construction, and operation phases, as on the Victoria Park Tunnel and the Waterview Connection projects.

John Munro Director, M&E New York, NY, US

Steven Kam-Hung LAI Director, Infrastructure, China Region Hong Kong

Kate Hunt Service Leader, Tunnel Ventilation & Fire Engineering (RMS), Rail & Transit Godalming, UK

Argun Bagis Principal Engineer, Tunnel Systems Australia, New Zealand

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tion plants. There are currently three tunnels in the early design phase with lengths expected to be in the 8-9 kilometre (5-5.6 mile) mark. • The current Australian policy to limit emissions at tunnel portals (see the article on “Long Road Tunnels and Portal Emission Control” in this issue) continues to be a major factor in increased energy use in Australian road tunnels. • The relatively hot Australian climate, principally in mid to north Australia, has made the effects of climate change a key consideration in the design of tunnel ventilation systems, particularly in relation to rail tun-

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Subway Tunnel Cross-Passage Spacing: A Performance-Based Approach by the late William D. Kennedy; Justin M. Edenbaum, Toronto, Canada, +1-917-225-6314, [email protected]; Mia Kang (formerly of Parsons Brinckerhoff); and Kirk G. Rummel (formerly of Parsons Brinckerhoff)

William D. Kennedy, an internationally recognized expert in tunnel ventilation, died in June 2012. During a 46year career with Parsons Brinckerhoff, he was instrumental in the development of tunnel ventilation systems for road and rail tunnels worldwide. His reputation in tunnel ventilation was recognized in March 2012 by the International Symposium on Tunnel Safety and Security, which awarded him its 2012 Achievement Award, citing his “long and illustrious career in ventilation engineering of tunnels” and calling his lifetime body of work “a shining example of wedding practice and theory in the design of tunnels.”

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This abstract is condensed from a paper that was originally prepared for the 2006 APTA Rail Conference and has been updated to reflect the current 2014 version of NFPA 130.

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The US National Fire Protection Association's Standard 130, "Fixed Guideway Transit and Passenger Rail Systems," requires that tunnel-to-tunnel cross-passages shall be spaced a maximum of 800 feet (244 meters) apart. No guidance is provided on how the actual spacing should be determined. Intuition says that the spacing should vary with the length of the train, the number of passengers on board the train, the walkway width, the design fire scenario, etc. This paper presents a performance-based approach for calculating cross-passage spacing for downstream emergency evacuations from the fire site, and discusses NFPA 130 compliant methodologies for reducing the numbers of cross-passages required. The performance-based calculations include the use of computer software for analyzing and comparing exiting strategies. The simulations account for the geometry of a bored tunnel.

Introduction Based on earlier emergency ventilation studies, it was concluded that the maximum cross-passage spacing should be such that those downstream of the fire could evacuate to a point of safety within the time that it takes for the floor of a train car to burn through (which leads to flashover of the entire train car). This leads to the conclusion that increasing the car-floor burn-through time would allow greater tunnel-to-tunnel cross-passage spacing and possibly reduce costs. This is suggested in NFPA 130 (Section 8.5.1.3.2(1)). Another possibility is wider walkways or cross-passage doors to speed passenger movement away from the fire site.

It also leads to the inference that an interior or post-flashover fire should not be allowed to stop a train in a tunnel. Driver override should allow the movement of the train to the nearest station even if a passenger activates the emergency brake. The analysis for this paper assumes that this is the circumstance and that the only fire that will stop a train in a tunnel is a below-car fire that critically damages the propulsion system or derails the train.

Physical Scenario for Computer Model Physical scenarios are simulated using computer modeling to predict the evacuation times for passengers downstream of the fire site to reach a point of safety. Seven cross-passage spacings, ten walkway widths, and one passenger load were analyzed. The computer model accounts for the unique geometry of a bored tunnel by considering shoulder space requirements. The simulation results provide sample engineering information to develop a sample of cost-effective alternatives without compromising safety. The physical scenario for modeling is selected to be typical of a heavy- or main-line rail passenger system. The results of this type of analyses are affected by many specific project factors. Therefore, the results provided in this paper MUST NOT be directly applied to any projects. See Figure 1 for data used. A number of assumptions were made in the model in order to be conservatively safe and simulate a reasonable worst case situation, such as:

Bored Tunnel Geometry

• The location of the fire is in the middle of the train. • The to-be evacuated train has a fire that is aligned with a cross-passage. • A population of rail passengers consists of typical “commuters” with a range of demographics and walking speeds. (When the given walkway is wide enough, the model allows faster individuals to overtake slower walkers.) • The fire scenario was assumed to be: - Time 0 minutes, fire ignition; - Time 5 minutes, fire reaches below-car fire heat release rate; - Time 10 minutes, fire stops train; and - Time 15 minutes, evacuation begins.

Cross-passage spacing is particularly important in bored tunnel construction where cross-passages have to be mined in poor soil. Costs to construct each cross-passage in this situation can be high. The SIMULEX model inputs are adjusted for a bored tunnel construction. This leads to the concept of “Constructed Width” vs. “Effective Width.” Constructed Width is the actual width of walkway on the ground. Effective Width refers to the width entered into the SIMULEX model to accurately simulate the evacuation, relating to factors such as walkway width at shoulder height and the natural inhibition of walking near the edge of an empty track. Figure 2 presents the results of the simulations for 250 people per car and seven cars being evacuated.

Therefore, when calculating the minimum car-floor burnthrough time required, 10 minutes (15-5) should be added to the evacuation time. This does not include any allowance for modeling accuracy.

Some observations

• Clearly the spacing of cross-passages has a significant impact on evacuation times. For the assumed data, any evacuation times required to be lower than 30 minutes, with train capacities in this study range, and with reasonable walkway and cross-passage widths, require spacing of cross-passages significantly shorter than the 800 foot maximum in NFPA 130. Other variables such as walkway or cross-passage width would also have an impact. • There are significant benefits of wider walkways and wider cross-passage doors at cross-passage intervals above 700 feet or so. This is because the wider walkway after the train allows faster passengers to overtake slower passengers. In general, wider walkway widths help evacuation scenarios when the spacing has crosspassage doors that are not adjacent to the train and

The evacuation method was assumed to be all doors open to the walkway with movement to the nearest cross-passage downstream or adjacent to a stopped car. The passengers were considered to reach a point of safety after reaching 10 feet (3048 mm) inside of the cross-passage.

Downstream

595' (181 m)

Under-Car Fire

W X

X= Cross Passage Spacing

Upstream

X (200, 300, 400, 500, 600, 700, and 800 feet) (61, 91, 122,152, 183, 213, to 244 meters)

W= Constructed Walkway Width (36, 38, 40, 42, 44, 46, 48, 50, 52, and 54 inches) (914, 965, 1016, 1067, 1118, 1168, 1219, 1270, 1321, to 1372 mm)

Figure 1 – Evacuation Scenarios

"SIMULEX Users Manual"; 1998, Integrated Environmental Solutions, Limited; 141 St. James Road, Glasgow G4 0LT, Scotland. William D. Kennedy, Norris A. Harvey, and Silas K. Li, “Simulation of Escape from Rail Tunnels Using SIMULEX,” American Public Transportation Association (APTA), Boston, Massachusetts, June 2001.

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These observations are based on the sample data and should not be directly applied to other projects.

The emergency exiting analysis was done using the computer program SIMULEX1, which simulates the emergency exiting of people. The program algorithms for the movement of individuals are based on real-life data and predict realistic flow of people. It simulates the escape movement of each person instead of using a mathematical formula for uniform flow rates and average speeds of groups of people. This program is well-validated and has been used to model rail system emergency evacuations for a number of years2.

W

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2

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are located far away from the end of the 36:00 1200-foot Cross Passage Spacing train. Under these circumstances, wider 1000-foot Cross Passage Spacing 800-foot Cross Passage Spacing walkways can be considered as an alterCross 30:00 native to shorter cross-passage spacing. Passage Spacings • In the scenario adopted for analysis, it (feet) is obvious that shorter cross-passage in800 24:00 700 tervals (in the range of 200 to 500 feet) 600 result in one to three cross-passages 500 400 adjacent to the train immediately ac18:00 300 cessible as soon as the evacuees move 200 onto the walkway. Because the train can discharge passengers at a greater rate 12:00 than they can exit through cross-passages, the effect of wider walkways in these 06:00 shorter intervals is minimal. 34 38 42 48 50 54 • While not immediately apparent from the Constructed Walkway Width (inches) data shown, the effect on evacuation times due to varying passenger travel Figure 2 –Time vs. Width speeds is significant, again, at the lonpassage locations and widths, this approach could be ger intervals; of interest where continuous movement used to select car-floor burn-through times when cars is occurring as opposed to the accumulated congesare retrofitted or new rolling stock is ordered. For future tion immediately next to the train that dominates the designs, this approach could be used to develop a cost shorter spacing cases. Thus, if performing analysis analysis combining cross-passage spacing and widths, around cross-passage spacings that are beyond the car-floor burn-through time, and walkway width; possibly train, careful attention must be given to the model increasing the cross-passage spacing beyond the NFPA inputs for evacuation speeds. 130 maximum of 800 feet (244 meters). • Finally, the model examines the paths of evacuation up to the point of safety - the cross-passage. A close Recommendation examination of the dynamics of the evacuation paths After peer review this approach could be used to develsuggests that a project-specific application might want op an enhancement to NFPA 130. This enhancement, in to consider the entire evacuation path—to whatever relating cross-passage to other project characteristics, ends: a rescue train, a station platform, the opposite could provide a more logical basis for cross-passage bore trackway, etc. The effects of the complete path spacing that could be greater or lesser than the current should be modeled to study if there is an adverse af800-foot requirement (244 meters). fect of the evacuation in the non-incident tunnel. At a minimum, such analysis could suggest appropriate William D. “Bill” Kennedy was instrumental in the development instructional and training emphasis. Evacuation Time (min:sec)

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NETWORK

Conclusion A performance-based approach for estimating evacuation times downstream from a tunnel fire site and minimum car-floor burn-through times has been presented. It allows the trade-off among cross-passage spacing, car-floor burn-through time, and walkway and cross-passage door width. For existing systems with fixed cross-

of tunnel ventilation systems for road and rail tunnels worldwide and he led the development of the Subway Environmental System (SES) software program, widely considered the standard tool for the analysis and design of transit systems. Justin Edenbaum is a Supervising Mechanical Engineer in the Toronto office of Parsons Brinckerhoff specializing in tunnel ventilation and fire life safety.

A Note on Fixed Fire Fighting Systems in Road Tunnels by Anna Xiaohua Wang, New York, NY, US, +1-212-465-5756, [email protected]; and Norman Rhodes, New York, NY, US, +1-212-613-8861, [email protected]

Historically, the disappointing results of the Ofenegg Tunnel fire tests (1965, Switzerland) had a negative impact on sprinkler application in tunnels. The tests, which employed pools of aircraft fuel, led to the view that visibility was much reduced by the sprinkler systems and hot steam was generated that could cause scalding at long distances from the fire. The steam production also displaced smoke more quickly causing temperatures to be higher than without sprinklers. After extinguishment the fuel continued to evaporate, reaching critical concentrations within about 20 minutes. Subsequent deflagrations occurred that created air velocities of up to 30 meters per second. It was the impact of this experience that was reflected in the World Road Association (PIARC) recommendations which, between 1983 (World Road Congress in Sydney) and 2004, consistently advised against the installation of fixed fire fighting systems (FFFS) in road tunnels, and this position was reflected in US standards. One of the factors that maintained this attitude against the application of FFFS in tunnels was the fire sizes generally used. The fire sizes chosen on which to base the design were relatively small—20 to 30 MW—typical of a bus or truck fire. Such fires were regarded as manageable and ventilation systems were sized to control smoke for such events. Several severe road tunnel fires - the Mont Blanc Tunnel (France/Italy, 1999), the Tauern Tunnel (Austria, 1999), the St. Gotthard Tunnel (Switzerland, 2001), and the Frejus Tunnel (France/Italy, 2005) - resulted in loss of life, injury, and infrastructure damage that were far more extensive than if they had occurred on surface roadways. These fire incidents demonstrated that fire sizes could be much larger than 20-30 MW and completely changed the perception of the design fire size. Since then the maximum design fires utilized in tunnel design have increased as much as tenfold in some cases. These re-

cent incidents have emphasized the need for further improvement to be made in tunnel fire management; the FFFS is one technique that is actively being promoted.

Types of FFFS Several types of FFFS have been used in road tunnels worldwide: • Sprinkler/spray (water deluge) systems, based on dense water jets consisting of large-size droplets; • Water mist systems, based on very fine water droplets; and • Foam water suppression systems. Water sprinkler type FFFS have been installed in road tunnels of significant length for many years in Japan and Australia. Tunnels that have water deluge fixed fire fighting systems installed can also be found in the United States, Norway, Canada, and Sweden. These have been found to be effective in preventing fire spread and enhancing cooling of the tunnel structure. In 1999, two fires occurred in the underwater tunnels of the Tokyo Metropolitan Expressway and the FFFS helped control the fires so firefighters could approach and eventually extinguish the fires. The deluge system in Sydney Harbor Tunnel in Australia is reported to have worked well during a van fire in 2004. Another example is the Burnley Tunnel fire in 2007; the deluge system was activated quickly and this was deemed by firefighters to have kept the fire under control. Based on this experience, and the development of alternative types of FFFS, PIARC re-evaluated its position with regard to FFFS and at the same time the European Community undertook research programs to examine fire suppression and the impact of larger design fires. Several relevant European research programs, including UPTUN (Multinational European Research Project) and the SOLIT (Safety of Life in Tunnels) Project, have demonstrated through independent tunnel fire tests that, with early activation, high pressure water mist systems can be effective in controlling potential 200 MW solid fuel fires

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Introduction

Fire and Life Safety

NETWORK

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Fire and Life Safety

NETWORK and 200 MW diesel oil pool fires. The water mist systems have been installed in the A86 tunnel in Paris, the M30 tunnel in Madrid, the Roertunnel and the Tunnel Swalmen in the Netherlands, and other tunnels in Europe. Therefore, FFFS are now increasingly being considered in the design of tunnel systems worldwide. This position is also reflected in changes to the recent NFPA 502 and PIARC documentation.

Choosing a Fire Suppression System

Figure 1 – Water sprinkler nozzles in the tunnel

Choosing the type of fire suppression system for a road tunnel is not an easy decision to make. Some of the different aspects of the systems are as follows:

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Water Sprinkler Fire Protection System The water sprinkler fire protection system (see Figure 1) has existed for over 100 years and is a commonly used and reliable technology; deluge water sprinkler systems are the common FFFS in Australia and Japan. The system performs very well for Class A (solid fuel) fires, but is considered to be less suited for Class B (liquid fuel, oil) fires or where "splashing" of the fuel is to be avoided.

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Water Mist Fire Protection System Compared to the water sprinkler system, the water mist system (see Figure 2) generates much smaller water droplets and therefore has advantages in promoting more efficient gas-phase cooling and uses 2 to 3 times less water for road tunnels (depending on the system used). Both the water mist and water vapor system can measurably reduce radiant heat flux to objects near the fire - this helps firefighters approach the fire and provides better conditions for evacuation. However, because the system contains fine water particles, it may be less efficient in cooling or wetting the fuel surfaces; therefore, the system is less efficient to combat solid fuel fires compared with the water sprinkler system.

Figure 2 – Water mist nozzles in the tunnel

Piping Network Proportioning Controller

Figure 3 – Schematic of a foam-water sprinkler system

CAF Generation Water Releasing Controller Air

Piping Network Mixing Chamber

Foam Concentrate

Fixed Foam-Water Fire Suppression Systems Fixed foam-water fire suppression systems may be another alternative to combat tunnel fires. A foam agent is especially suited for the control and extinguishment of flammable and combustible liquid-type fires. There are two types of foam-water fire suppression systems proposed for road tunnels: • the foam-water sprinkler system (see Figure 3); and • the compressed air foam (CAF) system (see Figure 4). The use of the foam-water sprinkler system against diesel pool fires was investigated in the Memorial Tunnel

Nozzles

Alarm Check Valve Main Control Valve Water Supply

Bladder Tank

CAF Nozzles

Figure 4 – Schematic of a compressed air foam (CAF) system

in West Virginia by Bechtel/Parsons Brinckerhoff. The foam-water sprinkler deluge system has been installed in several tunnels in Seattle, Washington. The compressed air foam (CAF) system has been tested in road tunnels in the Netherlands. For both types of foam-water suppression systems, corrosion protection is required for the storage tanks and the pipe systems, and the system can be costly in the long run because of the corrosion problem associated with the use of foam agents.

• for the foam-water sprinkler system, the delivery time of the foam may be too long as the foam tanks have to be installed at the tunnel portals and it may take time for the foam to reach the fire if the fire is located in the middle of the tunnels; and • for the CAF system, additional mechanical rooms need to be installed at specific intervals of length in the tunnels which increases the initial capital cost of the installation of a CAF system.

Conclusion The FFFS is also being considered in road tunnels to reduce the size of the ventilation system required. When authorities prepare to permit all types of traffic, such as dangerous goods or heavy goods vehicles, to cope with increasing economic activities, mitigation options that can combat 200 - 300 MW fires would be necessary for tunnels, as recommended by NFPA 502 and most European standards. Without FFFS, large fires (such as 200 - 300 MW) dictate the need for a very powerful ventilation system, increasing space requirements and adding significant cost. In addition, FFFS, unlike a ventilation system, can provide benefits for firefighting, tunnel system protection, and operational continuity. Although the benefits of FFFS are clear, many design issues remain, such as: the reduction in the design fire size with the inclusion of the FFFS and the subsequent reduction in ventilation requirements; the impact of the FFFS on the structural protection system; the performance of the FFFS under operational conditions that have not been tested in the tunnel fire experiments; and the impact of the FFFS on the overall tunnel safety concept and operation procedures. The most reliable method available to date for those unsolved design questions is full-scale testing, but that is extremely expensive and impractical for new or existing tunnels. A computational fluid dynamics (CFD) fire modeling approach is an alternative and holds great promise once a reasonable correlation between numerical simulations and full-scale tests has been achieved. References • Haerter, “Fire Tests in the Ofenegg-Tunnel in 1965”, International Symposium on Catastrophic Tunnel Fires, Boros, Sweden, November 2003.

• PIARC 2008: Road Tunnels: An Assessment of Fixed Fire Fighting Systems. • UPTUN, Fire development and mitigation measures, Work Package 2 of the Research Project UPTUN, 2008. • Starke, H., “Fire Suppression in Road Tunnel Fires by a Water Mist System – Results of the SOLIT Project”, Fourth International Symposium on Tunnel Safety and Security, Frankfurt am Main, Germany, March 17-19, 2010. • Water Mist Fire Suppression Systems for Road Tunnels, Final Report, The SOLIT Research Project, 2007. • NFPA 502, Standard for Road Tunnels, Bridges, and Other Limited Access Highways, 2014 Edition, National Fire Protection Association. • Huijben, Ir. J.W., “Tests On Fire Detection Systems And Sprinkler in a Tunnel,” ITC Conference Basel 2-4, December 2002. • Liu, Z.G., Kashef, A., Lougheed, G., Kim, A.K., “Challenges for Use of Fixed Fire Suppression Systems in Road Tunnel Fire Protection”, NRCC -49232, Suppression & Detection Research Applications – A Technical Working Conference (SUPDET 2007), Orlando, Florida, 2007. • Quenneville, R., “The Emergence of CAF Fixed-Pipe Fire Suppression Systems”, Fire & Safety Magazine, Spring, 2006. • Memorial Tunnel Fire Ventilation Test Program, Test Report (section 8.10), Massachusetts Highway Department, by Bechtel/Parsons Brinckerhoff, Nov. 1995. • Lemaire, A.D. and Meeussen, V.J.A., “Effects of Water Mist on Real Large Tunnel Fires: Experimental Determination of BLEVE-risk and Tenability during Growth and Suppression”, Rept. 2008-Efectis-R0425, Efectis Nederland BV, June 2008. • Grant, G., Brenton, J., Drysdale, D., “Fire Suppression by Water Sprays,” Progress in Energy and Combustion Science 26 (2000), 79-130. • Tunnels Study Center (CETU), "Water Mists in Road Tunnel," State of knowledge and provisional assessment elements regarding their use, June 2010. • NFPA 15, Standard for Water Spray Fixed System for Fire Protection, 2007 Edition, National Fire Protection Association. Dr. Anna (Xiaohua) Wang is a Principal Technical Specialist in Parsons Brinckerhoff’s New York office. Dr. Norman Rhodes is the Technical Director of the Parsons Brinckerhoff Mechanical/Electrical Technical Excellence Center.

Fire and Life Safety

For longer tunnels, the use of foam-water fire suppression systems may be challenging:

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NETWORK

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Fixed Fire Fighting Systems in Road Tunnels – System Integration by Matt Bilson, New York, NY, US, +1-212-465-5510, [email protected]; and Sal Marsico, New York, NY, US, +1-212-465-5576, [email protected]

Introduction Fires that occur in road tunnels can grow rapidly and reach very high heat release rates. As a result, road tunnels are designed with mitigation technology and procedures to help reduce the detrimental effects that can occur. The main goals of the mitigation measures are to: • Provide a tenable environment for motorist evacuation; • Assist firefighters with their operations; and • Maintain the structural integrity of the tunnel.

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A fixed fire fighting system (FFFS) is one type of mitigation measure implemented to help achieve these goals. The major components of the FFFS include water delivery infrastructure (pumps, pipes, valves, and nozzles – divided into separate zones for water delivery) and also components for water removal (drainage, pumps, pipes, water treatment). A FFFS is typically installed to help reduce the fire growth rate and air/smoke temperature, which helps to prolong occupant tenability and provides structural protection. Proper integration of the FFFS with other tunnel fire-life safety systems is essential to achieve the FFFS goals.

Poor system integration can lead to a reduction in FFFS performance and fire safety.

System Integration with Fixed Fire Fighting Systems CCTV Activation of the FFFS at an early stage of a fire incident is the best way to assure optimal performance, and this is

Plan view of roadway:

179

178

CCTV vision example: LEGEND

Zone N178 is in the foreground Zone N179 is in the background

Figure 1 – Example of good CCTV and FFFS integration

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The first important question in FFFS integration is whether or not the tunnel has a full-time operator. In many tunnels with FFFS, a full-time operator is present. In this article the integration question is considered in the context of a full-time operator being present, but it is noted that if an operator is not present there will be different integration considerations. Tunnel systems and functions that require particular attention for integration with a FFFS, with full-time operator present, include: • Closed circuit television (CCTV); • Ventilation systems; • Egress provisions; • Drainage; • Fire alarm systems, control systems, heat detection systems; and • Traffic and operations.

Fixed camera

Traffic and airflow

Deluge zone/ventilation zone

Linear heat detector

Tunnel wall

Roadway

Bndry ampua kg/m2 10.00

Application criterion is 8 kg/ 2 m in one minute

Extra water due to zone overlap Plan view of tunnel water accumulation at roadway level

AIRFLOW

9.00

8.00

Airflow is right to left 30m (100 ft.)

30m (100 ft.)

FFFS Zone

FFFS Zone

7.00

Fire and Life Safety

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6.00

5.00 4.00

Jet fans Water overshooting zone of application (overshoot by up to 15m)

Jet fans Water not reaching entire zone of application (up to 5m of a zone missed)

3.00 2.00 1.00 0.00

Figure 2 – Example of FFFS and tunnel ventilation integration-CFD results

The figure shows an example of good systems integration with camera locations relative to their proximity to FFFS zones. Placing a camera within a zone, instead of at zone boundaries, may generate confusion for the operator because, instead of the CCTV image showing the start of a zone, the image would be starting halfway along the zone, requiring the operator to cycle through views to confirm the location. Ventilation The ventilation system in a tunnel is used to direct heat and smoke away from the egress path by producing a longitudinal tunnel air velocity flow in one direction (longitudinal ventilation); extracting the heat and smoke through vents along the tunnel (transverse ventilation); or a combination of the two. The air velocity can cause water in the FFFS’s water delivery region to shift away from the active zones. Computational fluid dynamics (CFD) results in Figure 2 show an example of the extent of water delivery drift for a longi-

tudinal ventilation system. In this example, activation of both the FFFS zone where the fire is located and one zone upstream mitigates drift effects. Careful zone activation can mitigate the effect of drift and provide assurance that water will reach the target. Jet fans near the FFFS zone should be activated only if necessary. In the region near a jet fan’s outlet there will be high velocity relative to the average velocity of the tunnel, which will exacerbate the water delivery drift. Egress Provisions Egress points (e.g., exit doors to escape passages) are generally positioned equidistant from each other along the tunnel and should be placed at the ends of the FFFS zones and not within active FFFS zones where egress may be hindered by visibility reduction, noise (the active FFFS is in fact very loud), physical restriction, and psychological stress. Placing egress points at the ends of a FFFS zone contributes to more streamlined egress. Firefighters using these egress points to enter the tunnel could experience significant disorientation if entering an active FFFS zone, thereby slowing their subsequent response. Drainage Drainage is another aspect to consider when installing an FFFS. In some systems, the very large flow rates of water mean that not all of the FFFS water will be captured at the drains within the zone of discharge, and practically there may be few design options to achieve this. The travelling fuel can create a risk of fire spread since the water can transport the fuel away from the

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typically accomplished through manual activation by the tunnel operator. The tunnel operator relies on the CCTV system to assist in identifying the fire location, as the CCTV system would typically detect smoke or stalled traffic well before a heat detector senses the fire. Once the fire has been located, the operator activates the corresponding FFFS zone. It is imperative that operators can easily and accurately identify the fire locations. Figure 1 provides an example of effective design integration between a CCTV and FFFS system.

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Figure 3 – Effect on visibility due to FFFS

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fire site. The fuel draining away from the fire site would be unshielded by vehicles and so it will typically be suppressed, if it is burning, prior to exiting the FFFS zone. Flame traps in the drainage system are sometimes used to prevent a secondary fire moving through the drain pipe network.

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Fire Alarm Systems, Control Systems, and Heat Detection Road tunnels can be fitted with automatic and/or manually activated FFFS. In a manually operated system, operators are provided with a CCTV system to identify the fire location, so that they are able to activate the FFFS in the appropriate zone(s), as described above. In some instances a back-up automatic activation system is provided. This system typically uses a linear heat detector (LHD) to identify the fire location. Once the LHD signal is received at the control panel, a countdown timer activates. If no response is made by the operator within the allotted time, the FFFS is deployed. The LHD is an addressable sensing cable which can detect absolute temperature or rate-of-rise, with each detection zone coincident with a specific FFFS zone. In the case of an automated response, the following items support good system integration: • FFFS and LHD zones are to be coincident. • The FFFS should activate in the first LHD zone to detect heat and the adjacent zone upstream. • Any further LHD activations must not trigger any additional FFFS zone activations (as explained below). The system must be programmed such that the operator can override an automated response if necessary. Automated systems are capable of executing ineffective responses, so it is up to the operator to make the final operational decisions. For example, in a tunnel, heat will travel over a large number of FFFS zones and trip the LHD

in zones remote from the incident. If all of these zones were to discharge water, there may not be enough water capacity available in the incident zone to suppress the fire (a FFFS can be feasibly designed with enough water supply capacity to feed two or three zones). Conversely, the fire can propagate or the operator may need to correct their choice, which means the operator needs to have the ability to shut zones off and start others. Traffic and Operations After a fire is identified, traffic must no longer be allowed to flow into the tunnel. In unidirectional traffic, the vehicles downstream of the fire are expected to exit the tunnel while those upstream are expected to stop (a common assumption in tunnel fire-life safety design). The system must be designed so that the FFFS is never activated over live traffic. An activated FFFS will reduce motorist visibility and vehicle traction, which increases the chance of a vehicle collision and exacerbates the emergency, or worse still, creates an unsafe situation (see Figure 3).

Conclusion An FFFS is a useful fire safety tool for a road tunnel. Good integration of the FFFS with other tunnel systems and functions, using the principles outlined above, assists in bringing to fruition its purported benefits for tunnel fire safety. In addition to the engineered systems, it is important that the tunnel operator is well-trained and that tunnel systems are well-maintained to assure good performance. Matt Bilson is a Principal Technical Specialist in the field of tunnel ventilation and fire-life safety in the New York office of Parsons Brinckerhoff. Sal Marsico is a Mechanical Engineer in the field of tunnel ventilation and fire-life safety in the New York office of Parsons Brinckerhoff.

Fire-Life Safety and System Integration: The Functional Mode Table by Matt Bilson, New York, NY, US, +1-212-465-5510, [email protected]; and Andrew Gouge, New York, NY, US

Introduction

INCIDENT AND MODE ID

A fire or other emergency situation in a tunnel environment can be a serious threat to human life and the infrastructure. One of the main tasks of the fire-life safety (FLS) engineer is to develop a response strategy to manage or prevent such events. The strategy will frequently rely on many sub-systems such as ventilation, lighting and signage, traffic management, alarms, operator responses and coordination, and communication with emergency services agencies (e.g., the fire department). The harmonious and correct operation of the subsystems is essential to protecting life and infrastructure during an incident; clear and concise system integration is needed to achieve this goal.

Incident ID (as per the operator’s incident response plans)

Requirements and Architecture

Traffic Devices

Automatic

Communications

Escalation Modes

Lighting/ Signs

Fixed Fire Fighting System

Figure 2 – Functional Mode Table concept outline

Functional Mode Table (FMT) is proposed herein as a tool to assist in this exercise. The FMT, in principle, is a high-level computer program for tunnel operation during a given emergency scenario. It is a matrix of instructions that spells out in a detail how each sub-system must respond for a given emergency incident. It is based on an incident type, the means of detection, and the sub-system responses required (see Figure 2).

Operation and Maintenance

System Verification and Validation

Detail

Integration Test and Verification

Detailed Design

Manual

Implementation Time

The goal of the FMT is to assure that all major players in the tunnel’s fire-life safety – the FLS engineer, the implementation engineers, the operator, and emergency services workers – will work to a common framework, thereby improving implementation, commissioning, training, thereby maximizing the probability of a favorable outcome if an emergency occurs. Subsequent system responses for an incident can be pre-programmed using the FMT, reducing the complexity and burden placed on the tunnel operator.

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Concept

SUB-SYSTEM RESPONSES

Ventilation

Integration is not a new concept as exemplified by the “V” diagram (see Figure 1) which is a well-known concept in systems engineering. However, FLS relies on more than just systems integration; it is also necessary to combine the emergency incident plans with the design concepts and operator training. The concept of the

The functional mode table is set out between Concept and Requirements/Architecture phases. It is then used at every level of the process.

DETECTION METHODS AND LOCATION

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Figure 1 – The “V” diagram and the Functional Mode Table relationship

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NETWORK Case Study – An Urban Road Tunnel To illustrate the FMT concept, a virtual case study of an urban road tunnel several kilometers long is used. For the present discussion the tunnel is taken to have the following principal system features:

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• Unidirectional traffic; • Longitudinal ventilation; • Egress points at 200 meter spacing (to an adjacent tunnel); • CCTV system; • Fixed fire fighting system; • Communications (phones, public address), lighting, traffic controls; and • Full-time tunnel operator.

Response

Sub-systems available

Operator

Activate sub-systems and adjust response as incident progresses, contact fire department and other emergency services, and deploy staff where possible.

Human-machine interface.

Traffic management

Stop vehicles upstream of the fire and have vehicles downstream exit the tunnel.

Lane use signs, signals, portal barriers, and variable message signs.

Ventilation

Direct smoke downstream of the fire, away from people upstream.

Jet fans and axial exhaust fans.

Lighting

Provide direction to exits, assist Low-level lights, door with exit identification. strobes, tunnel lights, and door identification lights.

Detection and

Identify incident, and then

Radio rebroadcast, tunnel

alarms initiate and direct evacuation. public address, variable The ventilation system plays a major role in message signs, CCTV, life-safety, directing smoke downstream of and heat detectors. the fire so that people upstream are protectFixed fire Activate system in the correct Valves and pumps, and ed (see Figure 3). However, the ventilation fighting location. CCTV for identification. system system alone will not necessarily produce a favorable outcome; a successful outcome needs several provisions to operate correctly. Table 1 – Sub-system response for a road tunnel fire During a major incident, ventilation operation • During an emergency an operator’s capacity to is only one of several important steps that need to be perform sophisticated system adjustments may be taken, as explained in Table 1. limited by the enormous flow of information among the operator, the motorists, and the emergency Overcoming Operational Complexity – The FMT and a agencies. An operator’s attention becomes focused One Button Response on specific events and as a result may fail to take into Table 1 outlines a number of sub-systems required account the broader situation, a condition referred to to operate during an emergency, and a major tunnel as “attention tunneling”. will typically have a full-time and well-trained operator. • Emergencies do not occur frequently and so the operator However, it is not reasonable to expect the operator has limited practice at performing the required actions. to manually perform all of the actions required for the • Emergency situations are high stress events within the following reasons: control room. Designers of the systems need to be mindful of the possibility for an operator to “lock up” • Operators are typically not engineers and therefore not which could further delay the correct response. versed in tunnel systems design.

Jet fans are used to direct smoke downstream

Egress: back up the tunnel and via exit

Traffic upstream is told to stop

Figure 3 – Road tunnel fire-life safety concept

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System

Fire

Traffic drives out of the tunnel downstream

Fire-Life Safety and Ventilation Concept Design

Operator Emergency Services Occupants

Control System Design

FUNCTIONAL MODE TABLE

Systems (Detection, Alarm, Egress, Traffic Light, Lighting, Ventilation)

FUNCTIONAL MODE TABLE

Mechanical Design

Electrical Design

Figure 4 – Functional Mode Table links

Figure 5 – Functional Mode Table design links

System integration and programming of the control system to automate much of the incident response is required for the essential actions to take place. It is critical that the responses required with each sub-system for defined emergency scenarios have a simple yet methodical procedure. The FMT provides this procedure. It is the connection among the fire safety engineer, the programmers developing the control system’s detailed automatic routines, the system hardware, and the tunnel operator (see Figure 4). The FMT also forms a critical link at the design level (see Figure 5).

Generating a one button response requires that all stakeholders in the emergency response system are aware of the realistic information available during an emergency situation and the order of actions to be taken. As fire-life safety engineers, it is our responsibility not only to define the spectrum of data and available actions, but also to define the data with language, terminology, and structured presentation that is easily communicated and understood by other stakeholders. This task is challenging but not out of reach.

Given the number and complexity of tunnel systems, the burden on the tunnel operator needs to be minimized. If the operator has “too many clicks” to initiate at his/ her interface, it will slow the response and increase the chances of errors. In the “one button response” the systems are configured in a way that, once the operator provides essential information, a pre-programmed response is enacted. The FMT provides a framework for this and a simple example is provided in Table 2. Detection Devices ID

Comment

For example, with a well-designed FMT and incident response plan, during a fire in a road tunnel the operator would need to answer some basic questions at each stage in order to then activate the physical tunnel systems. Table 3 provides a simplified account of the response stages, questions, and system actions. The outline of questions in Table 3 minimizes the amount of information that the operator must give, thus reducing the time it takes for a response and maximizing the chances that the correct system actions will be taken and all the essential sub-systems will be activated. Traffic Devices – Incident Tunnel

Egress Devices

Ventilation

Manual

Auto

Escalation mode

Upstream from incident

D’stream from incident

Portal

Lights, PA, VMS

Jet fans

1

Suspected fire

CCTV

Heat sensor

Mode 2

Stop traffic

Exit with caution

Stop traffic

N/A

On, emergency mode

2

Confirmed fire

Operator

N/A

N/A

Stop traffic

Exit with caution

Stop traffic

On, egress mode

On, emergency mode

DECEMBER 2014 http://www.pbworld.com/news/publications.aspx

Incidents and Response Plans

Fire and Life Safety

NETWORK

Table 2 – Functional mode table example (showing a limited number of incidents and devices)

21

Fire and Life Safety

NETWORK

Stage of response

Operator inputs (to generate the “one button” response)

Pre-programmed system actions once incident confirmed (via the Functional Mode Table programs)

1. What kind of incident? Initial – suspected fire in roadway

2. Where is the incident (camera ID)?

Activate radio rebroadcast message warning people.

3. Confirm incident?

Activate emergency ventilation mode.

Operator has provided enough information, and the system can now simultaneously execute commands to operate the many sub-systems.

Close tunnels to traffic, change traffic signals and messaging in tunnel to tell people to stop if they are upstream of the fire.

Secondary – evacuation required

Is evacuation required?

Tertiary – fixed fire fighting required

Is fixed fire fighting needed?

Activate messaging, public address and radio rebroadcast to require evacuation. Activate lighting to guide people and warn vehicles in the other tunnel. Activate the system based on the incident location determined from the camera ID or linear heat detector zone.

Table 3 – Operator response concept – “one button” concept

The operator may need to make adjustments later, possibly manual adjustments, but with this framework the initial response and activation of critical systems for firelife safety are certain.

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The example presented assumes an automated control system that will activate all appropriate systems. However, in preliminary discussion with tunnel operators that work with antiquated or ill-equipped control systems, a similar approach can be taken with the use of clearly defined hardcopy instructions. In summary, the format, language, and terminology of the FMT are critical for operator interpretation and response in an actual emergency situation.

22

Fire-Life Safety Standards NFPA 502: Standard for Road Tunnels, Bridges, and Other Limited Access Highways 2014 edition requires that a road tunnel have an emergency response plan, developed by the agency responsible for operating the tunnel. The standard requires that the plan state how the various systems will operate for a given incident. The FMT paradigm encourages a one-to-one match between the emergency response plan incidents used by the operator, and the subsequent incidents used by the system developers in the system programming. This can have significant advantages for an integrated response between the operator and the system programmers because both parties are working to the same terminology. In addition, NFPA publishes a standard that is pertinent to the role of the FMT. NFPA 3: Recommended Practice for Commissioning and Integrated Testing of Fire Protection and Life Safety Systems, outlines a systematic approach

for the owner and the design team to provide documented confirmation that fire protection and life safety systems function as intended. The standard addresses the procedural concepts of fire-life safety system commissioning and also provides direction on the integrated system tests—tasks with which the FMT can assist.

Conclusion A well-integrated tunnel system will provide better functionality at all stages of a project including planning, implementation, commissioning, training, and operation. The FMT is a tool to assist with integrating the key stakeholders in the tunnel system design process including the operator, the designer, people who use the facility, the implementation staff, and emergency services. One of the greatest advantages of the approach is that it can be used to simplify the operator’s actions during an emergency, thereby improving the chances of a favorable outcome and greatly contributing to public safety. As a leading consultant in fire-life safety engineering, Parsons Brinckerhoff is well placed to improve the delivery and perception of fire-life safety training and operation within tunnels for our clients. The FMT can help to achieve this and provide a safer road or rail facility. Matt Bilson is a Principal Technical Specialist in the field of tunnel ventilation and fire-life safety in the New York office of Parsons Brinckerhoff. Andrew Gouge is a Senior Controls Engineer in the field of tunnel ventilation and fire-life safety. He left Parsons Brinckerhoff in 2014 to pursue an MBA.

Using Quantified Risk Assessment to Inform Ventilation System Responses by Kate Hunt, Godalming, UK, +44 (0)1483 528966, [email protected]

The tunnel ventilation system for the metro line described in this article was designed in the late 20th century. It provides comfort cooling and smoke control and was based on a fixed block signalling system that allowed only a single train in any ventilation section. Commercial pressures to enhance timetable capacity resulted in a signalling upgrade to train-based control (“moving block” signalling), which permits up to three trains to simultaneously occupy a ventilation section. The client wished to understand the risk impact of this change and in particular how the ventilation system should now be operated to best effect in the unlikely event of a tunnel fire. Parsons Brinckerhoff performed a comparative quantitative risk assessment (QRA), using available fire frequency data, to understand the impact of the ventilation system operation on the level of risk. This article describes the work and presents our findings.

Review of available fire frequency and consequence data The client had comprehensive data covering fire events on its network over the past 20 years. Of the 7,291 records reviewed, 384 related to the line on which we were working and only 18 related to the area of interest. Electrical arcing initiated the majority of the relevant fire events, at 175 (45.6 percent); arson accounted for 32 fires (8.3 percent); overheating equipment a further 22 (5.7 percent); and the remainder had a variety of causes, or were listed as “other/unknown”. The data demonstrated that the operator experiences a modest number of fire events, the vast majority of which are small events that are managed by day-to-day operational staff with minor to insignificant consequences for passenger and staff safety. We concluded that fires could be categorised broadly as:

• “Small” in-car fires (up to around 200kW) – “common arson events” using readily available materials such as newspapers and unlikely to cause a major fire; • “Small” undercar/track/tunnel fires; • “Large” in-car fires (greater than 1MW) – “determined arson events” involving a quantity of accelerant and sufficient to cause a major conflagration (thankfully, to date no such event has occurred on the network); and • “Large” undercar/track/tunnel fires.

The QRA analysis A set of event trees was developed, using known initiating events and with various possible outcomes shown on different branches. The significant inputs were as follows: • Frequency of initiating fire event (small or large fire, incar or undercar/track/tunnel); • Number of trains in section (1, 2, or 3); • Train reaches next station (yes/no); • Ventilation mode selected (remain in comfort cooling, switch off, select optimum smoke control mode, select sub-optimal smoke control mode); • Smoke control achieved (yes/no); • Smoke ingress into passenger compartment (yes/no); • Driver controls passengers (yes/no); • Passengers remain on train (yes/no); and • Protection implemented for evacuating passengers (yes/no). The probability of each outcome was determined in consultation with the client. Some were easy to define, such as the number of trains in a single ventilation section (33 percent probability of each possibility under new signalling system), while others required more detailed consideration, for example the probability of smoke being drawn into the passenger compartment. The client’s own modelling team undertook computer analyses to determine whether smoke control would be achieved with multiple trains in a ventilation section.

DECEMBER 2014 http://www.pbworld.com/news/publications.aspx

Abstract

Ventilation Fire Tunnel and Water Life Systems Systems Safety Power

NETWORK

23

Ventilation Fire and Life Systems Safety

NETWORK Event

Small in-car fire

Large in-car fire

Small under-car / tunnel fire

Large under-car / tunnel fire

Trains in section (1, 2, or 3 max)

33.3%

33.3%

33.3%

33.3%

Train reaches next station (not immobilised) (IT = incident train), AT = adjacent train, TT = third train)

IT 99.8% AT 99.8% TT 99.8%

IT 99% AT Null TT Null

IT 95% AT Null TT Null

IT 66.5% AT Null TT Null

Change of ventilation mode (4 modes) (No change, Off, Optimal smoke control mode, Other smoke control mode)

25%

25%

25%

25%

IT = 10% or Null

IT = 5% or 50%

IT = 10% or Null

IT = 5% or 50%

AT & TT = 50% or Null

AT & TT = 5% or Null

AT & TT = 50% or Null

AT & TT = 5% or Null

Critical velocity achieved IT = Null

IT as appropriate

Smoke ingress into passenger compartment

Null

Driver effectively controls passengers (client data)

96.367%

96.367%

96.367%

96.367%

Passengers remain in situ

85%

85%

85%

85%

Protection implemented for evacuation

96.7%

96.7%

96.7%

96.7%

Maximum fatalities per incident

IT = 3 AT = 0 TT = 0

IT = 1400 AT = 1050 TT = 700

IT = 3 AT = 0 TT = 0

IT = 1400 AT = 1050 TT = 700

AT & TT 0% or 100% as appropriate

As appropriate

AT & TT 0% or 100% as appropriate

Figure 1 – Probabilities and consequences used in the QRA event trees

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These analyses suggested that critical velocity1 would be met with two trains in section but if three trains were present, critical velocity would be lost at the incident train but achieved at the non-incident trains due to cooling of the smoke along the tunnel length. The probabilities agreed are shown in Figure 1 above. Four event trees were then constructed and the resulting relative risk levels were reviewed.

Results of the QRA Figure 2 shows the impact on each scenario of leaving the ventilation in a comfort cooling mode (no change), switching it off, setting it to a non-optimal mode, and setting it to the optimal smoke control mode. Note that with a moving block signalling system, the following trains could be close to the train in front (around 25 metres apart). The train positions shown in Figure 2 are not intended to convey an accurate location for each train. Shaded results show an appreciable increase in risk due to the ventilation configuration selected. The worst case outcome for a small fire was essentially the same for all ventilation configurations: operating the ventilation system gave no material benefit, regardless of the number of trains in the ventilation section. However, there was no disadvantage in using it. Therefore, since staff may not

know whether a fire is “small” or “large”, the ventilation response derived for large fires was considered acceptable for small fires as well. For large fires, the presence of additional trains has a marked effect on likely risk level. For a single train event, there is a modest benefit in operating the ventilation system in the optimal mode (although for a fire near the centre of the train, even the optimal mode may incur a large loss of life). When there are multiple trains in a section, however, the impact of using the optimal ventilation mode offers a substantial benefit for a large fire incident, even if critical velocity is lost over the incident train.

Conclusions and recommendations The comparative QRA proved an important tool for decision making. The structured event trees allowed various ventilation options to be tested and the clear outcome guided changes to maximise safety on this railway. It showed that the optimal smoke control mode gave a significant benefit for large in-car and undercar fires, with the greatest benefit when there are multiple trains in the ventilation section. For small undercar fires, using the optimal smoke control mode also gave a fractional benefit, since it reduced the tendency for smoke ingress into the incident train.

Critical velocity – the air flow required to prevent smoke from moving upstream of the fire location.

1

24

Results: Worst case average number of fatalities per 1000 years

Direction of travel

critical velocity met

Scenario

No Change

Switch Off

NonOptimal

Optimal

“Small” in-car fire (common arson event)

2.34

2.60

2.60

2.60

“Small” undercar/track/ tunnel fire

26.35

29.27

30.90

30.90

“Large” in-car fire (determined arson event)

1.21

1.27

1.27

0.46

“Large” undercar/track/ tunnel fire

29.24

30.78

32.49

4.28

Ventilation Fire and Life Systems Safety

NETWORK

Results: Worst case average number of fatalities per 1000 years

Direction of travel

critical velocity met

critical velocity met

Scenario

No Change

Switch Off

NonOptimal

Optimal

“Small” in-car fire (common arson event)

2.34

2.60

2.60

2.60

“Small” undercar/track/ tunnel fire

26.35

29.27

30.90

30.90

“Large” in-car fire (determined arson event)

118.97

125.23

125.23

0.46

“Large” undercar/track/ tunnel fire

98.35

103.53

105.24

4.28

Results: Worst case average number of fatalities per 1000 years

Direction of travel

critical velocity lost

critical velocity met

critical velocity met

Scenario

No Change

Switch Off

NonOptimal

Optimal

“Small” in-car fire (common arson event)

2.34

2.60

2.60

2.60

“Small” undercar/track/ tunnel fire

26.35

29.27

30.90

30.90

“Large” in-car fire (determined arson event)

197.48

207.87

187.88

0.68

“Large” undercar/track/ tunnel fire

144.42

152.02

153.73

8.58

Figure 2 – Impact of differing ventilation responses to various scenarios Incident train condition

Recommended actions

1

Incident train can move to next station

Move train to next station using any driving mode. Evacuate train and respond to fire incident at station.

1

Incident train cannot move (incident train immobilised or platform not available)

1) Establish driver’s intended evacuation direction. 2) Use optimal smoke control mode to move smoke in opposite direction. 3) Evacuate train and respond to fire incident in situ.

2 or more

Incident train can move to next station

1) Use optimal smoke control mode to move smoke forward, and 2) Move train(s) in front to the next station at low speed, and 3) Move incident train to next station using any driving mode. Evacuate train and respond to fire incident at the station. 4) Move or evacuate trains behind the incident on a case-by-case basis.

2 or more

Incident train cannot move (incident train immobilised or platform not available)

1) Use optimal smoke control mode to move smoke forward, and 2) Move train(s) in front to the next station at low speed, and 3) Evacuate train and respond to fire incident in situ. 4) Move or evacuate trains behind the incident on a case-by-case basis.

Figure 3 – Table of recommended actions

When there is one train in a ventilation section, the optimal smoke control mode should be determined based on the fire location along the train and the driver’s intended direction of evacuation. When there is more than one train in the ventilation section, trains in front of the incident train should be driven forward at low speed, out of the ventilation section. The preferred direction of ventilation should then be forward, to avoid passing smoke

over the trains that follow. Figure 3 summarises the recommended actions. Kate Hunt is the Tunnel Ventilation & Fire Engineering Service Leader for the UK. She has over 20 years’ experience in the design and analysis of tunnel ventilation systems and in developing operational strategies for tunnel ventilation systems for road, rail, metro, and cable tunnel applications.

DECEMBER 2014 http://www.pbworld.com/news/publications.aspx

Number of trains in section

25

Ventilation Fire and Life Systems Safety

NETWORK

A Risk-Based Approach to Jet Fan Optimisation by Anthony Ridley, Godalming, UK, +44(0)1483-52-8661, [email protected]

Introduction In addition to providing adequate air quality and maintaining temperatures within acceptable limits, tunnel ventilation systems need to be designed to move smoke in the event of a fire with a ‘good’ level of confidence. Wind and other meteorological forces can negatively affect the performance of the ventilation system, but for how much wind force should the system be designed?

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Parsons Brinckerhoff’s UK tunnel ventilation team is working on a large railway project with a number of tunnels, so it was important to answer this question confidently and with a solid basis. Risk analysis was used as a tool to help the decision-making process.

26

This article focuses on the optimisation of a range of rail tunnels that would utilise jet fans to provide smoke control in the form of longitudinal ventilation. Longitudinal ventilation prevents smoke from back-layering, providing a tenable evacuation environment upstream of the fire. In total, seven tunnels with lengths ranging from approximately 500 metres to 3 kilometres were analysed.

was provided to handle other random failures. A further question arose as to the probability of both a high wind and a failed jet fan. Was the investment in the redundant jet fan warranted? A quantitative risk analysis was therefore undertaken to understand the acceptability of this risk of removing the redundant jet fan. The combination of a fire in the tunnel, a high wind force, and a failure of one of the required jet fans might lead to the back-layering of smoke within the tunnel. Backlayering occurs when the ventilation flow rate is not high enough to meet ‘critical velocity’1 (CV). The critical velocity will depend on factors such as the fire heat release rate and tunnel gradient. The consequences associated with providing less than critical velocity required evaluation.

Methodology An event tree was generated to consider the probability of various scenarios (see Figure 1). Each branch or scenario of the event tree had an overall predicted event frequency and consequence assigned. This was subsequently used to estimate risk.

The optimisation was carried out after an initial design phase where the tunnels were found to be sensitive to atmospheric wind. At that stage of the design, questions still remained as to whether the wind force that was being designed for was reasonable. We based the design on a 1 percent probability of exceedance in any year, but should it be 10 percent, 1 percent, 0.1 percent, or something different?

A tunnel fire frequency rate was estimated through interpretation of statistical data from the UK’s Railway Safety and Standards Board. Various probabilities were then assigned to each scenario.

The design included an assumption that the jet fan nearest the fire was inoperable. In the emerging design, approximately one jet fan per portal was required to overcome the wind forces, two jet fans were required to control the smoke, and one standby/redundant jet fan

• Bulk-flow simulations were undertaken using the Subway Environment Simulation (SES)2 software for three representative tunnels. This provided information about the tunnel air flow rate for every different configuration of ventilation mode, train location, fire heat release rate,

Each event path required an evaluation of consequences to passengers. The consequence analysis was broken down into two constituent parts:

Critical velocity – the air flow required to prevent smoke from moving upstream of the fire location. Subway Environmental Design Handbook. Volume II. Subway Environment Simulation Computer Program (SES). Part 1. Prepared by Parsons Brinckerhoff as part of a joint venture for the U.S. Department of Transportation, in 1975.

1 2

Common Tunnel fire Ventilation frequency with cause failure mode achieved consequence No

Design

Fire magnitude

Wind direction

7MW

Adverse

Wind strength Consequence (percentage exceedance)

Consequence*final event frequency

10% 1%

Ventilation Fire and Life Systems Safety

NETWORK

0.1% 0.01%

Beneficial

All

1MW

30MW Base

Fail SUM Yes

ventilation direction, and wind force that was tested. From this, average percentage of critical velocity was determined for each combination of tunnel, ventilation mode, and wind condition. • A 3-D analysis was then performed on a characteristic short tunnel section using the Fire Dynamics Simulator (FDS) software. The evacuation model was enacted within the software which allowed the coincident location of the smoke and passengers to be predicted. These simulated the evacuation of 1,100 passengers within the tunnel with different fire heat release rates and air flow rates. Predicted effects or consequences to passengers during the evacuations were recorded based on the Fractional Effective Dose (FED) method, but adjusted for these simulations to also account for the effects of irritant gasses. The simulations were undertaken for different airflow rates to allow the outcomes to be mapped to the SES simulations.

Results The results of the consequence analysis can be seen in Figure 2. It is evident that for the larger fires simulated there is always a base equivalent fatality rate of approximately 55 persons. This represents the inherent consequence involved with longitudinal ventilation systems; there is a risk that passengers may be located downstream of the fire location. To minimise passenger numbers downstream of the fire, the ventilation direction is decided by the fire location. To model a condition where an “average” number of passengers were downstream of the fire, the fire was set to be a quarter of the length down the train. As the percentage of critical velocity achieved reduces, the backlayering of the smoke advances. This process is illustrated in Figure 3. The jump in the predicted number of equivalent fatalities from 55 to 250 as seen in Figure 2 was due to the back layering of smoke past an upstream passenger exit (illustrated by scenario C in Figure 3).

DECEMBER 2014 http://www.pbworld.com/news/publications.aspx

Figure 1 - Event tree (dotted arrows represent uncompleted branches of the tree, only one complete branch is fully shown)

27

350.0 300.0

Equivalent Fatalities

Ventilation Fire and Life Systems Safety

NETWORK

250.0 30MW

200.0

7MW

150.0

1MW

100.0 50.0 0.0

0%

20%

40%

60%

80%

100%

% Critical Velocity Figure 2 - Predicted relationship between percent of critical velocity achieved and total passenger fatalities and weighted injuries for different fire magnitudes. a) CV is achieved

b) CV not achieved but no additional passenger fatalities (60 - 100% CV)

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c) CV not achieved and resulted in additional passenger fatalities (27%)

3280

Point A: 3748 (>14%) Point B: 3632 (>11%)

1st Peak (Pa)

492

Point A: 571 (>16%) Point B: 557 (>13%)

667

Point A: 719 (>8%) Point B: 700 (>5%)

2nd Peak (Pa)

554

Point A: 470 (5%)

Table 2 - Comparison of pressure parameters from experiment and ThermoTun results

58

2

-400

ThermoTun software is for studying pressure waves within high speed train tunnels. Since ThermoTun is a 1-D approach, some Figure 8 - Cisalpino ETR 470 natural disadvantages that may affect the accuracy are raised below:

DECEMBER 2014 http://www.pbworld.com/news/publications.aspx

500

The time required to complete the analysis was several hours from modelling to result analysis. With the balance between result accuracy and time requirement, ThermoTun has its own advantage over the 3-D CFD approach.

Discussions and Conclusions We conducted and compared 3-D CFD simulations against the full-scale experimental results. With the two train speeds analyzed (177.5kph and 204kph), the comparison of the pressure values at a specific measurement point inside the tunnel indicate that 3-D CFD simulations could generally model the pressure wave variation with a proper prediction of the wave pattern. However, the exception is the peak values of the first maximum positive pressure. The 3-D CFD simulations appear to provide an improper pressure magnitude. The findings in fact are similar to the axisymmetrical model used in a previous study6. To enhance the accuracy of CFD approach, further investigation of the numerical methods used is necessary. Due to the long turn-around time for the 3-D CFD simulation, it is recommended that such further investigation first be conducted on the axisymmetrical model before being extended to 3-D.

Even with the use of the latest high performance parallel processing technique, the overall progress of 3-D CFD simulation is very slow. The computational resources and time span required also prohibit the use of the 3-D CFD method as a design tool for high-speed railway aerodynamics analysis. The 1-D ThermoTun approach cost less to run the same scenario compared to 3-D. Although the ThermoTun simulation amplifies the pressure peak, for design applications this can be treated as a safety factor. In short, with more numerical method refinement and enhancement of computer speed and capacity, 3-D CFD is expected to perform more accurately and provide more detail when simulating tunnel pressure waves. However, with the current computational resources and the time span required, the 3-D CFD approach cannot achieve more accuracy within reasonable time and cost. It is concluded that 1-D ThermoTun is the best choice for engineering design purposes under current technology. Dr. Dicken K.H. Wu specializes in computational fluid dynamics (CFD) simulations and various types of computer simulation analysis. He has designed pressure comfort control systems for high-speed subway systems in Hong Kong, Mainland China, and Taiwan.7 Rambo RB Ye was formerly a specialist in simulation methods at Parsons Brinckerhoff.

“Aerodynamic design of underground station with high-speed train passing”, D.K.H. WU, 13th International Symposium on the Aerodynamics and Ventilation of Vehicle Tunnels, Organized by BHRA Fluid Engineering, 2009. An abstract of the same paper is in Network #70, November 2009, p 26. 7 For a previous Network article by Dicken Wu and YF Pin about FLUENT, see “New and Efficient Techniques for Modeling and Meshing with FLUENT and FDS,” in “The Engineer’s Crystal Ball,” Network #70, November 2009, pp 4-6. 6

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The time axis is so adjusted that the pressure values and pattern could be compared in detail. Table 2 summarizes the key pressure parameters for detailed comparison.

Fire Pressure and Life Transient Safety

NETWORK

59

Climate Change Fire Tunnel and Water Stormwater Life Resiliency Systems Safety Power

NETWORK

Railway Cooling Challenges by Mark Gilbey, Godalming, UK, +44 (0)148 352 8506, [email protected]

Parsons Brinckerhoff has been providing engineering support to London Underground, the Buenos Aires Metro (Subterráneo de Buenos Aires), and the proposed UK High Speed 2 project in identifying, understanding, and overcoming the challenges associated with warming railways.

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The Challenges

60

Most of the heat in a rail tunnel emanates from the trains and train operations. London Underground and the Buenos Aires Metro are examples of metros currently accommodating passenger demand well above what was originally envisaged. With improvements in train signaling and control technology, higher train frequency can often be realized, creating the potential for warmer tunnels and reduced thermal comfort and safety. The higher train frequency can also be coupled with higher train speeds to meet passenger demands for reduced journey time. This means more braking kinetic energy to dissipate, and thus more heat. Another issue common to both of these metros is the desire to meet passenger expectations for rolling stock air conditioning. Failure to manage temperatures can increase discomfort for passengers, making the railway a less attractive transport mode. However, retrofitting air conditioning adds further heat into the tunnels. High Speed 2 (HS2), a planned UK high-speed rail network from London to Birmingham and to Manchester and Leeds, presents similar challenges, but the key factor in this railway has proven to be the very high train speeds, meaning that a very large quantity of kinetic energy is generated when the trains brake. A good proportion of this energy can be regenerated, but the remainder still presents a great thermal stress on the tunnel environment. An external challenge to railways relates to the changing climate. Railway infrastructure has a life of over 100 years and over this period reasonably foreseeable climate

change could cause warming of 1½ to 2 degrees C in the UK. Over time, the inside tunnel environment would experience change similar to the outside environment. Compounding the challenge, passengers entering a railway from a warmer temperature would be less willing and able to accept a warm condition on the trains. Failure to manage increasing temperatures in tunnels can also drive up operating costs by increasing the amount of energy required to cool the trains and stations. It could also cause safety concerns for passengers and staff if tunnel temperatures became so hot that the air conditioning of trains in tunnels cut out because their condensers could not reject their heat. Other in-tunnel equipment, such as electronic wayside communications and signalling equipment, can become less reliable and have a shorter life when operated in higher temperatures. For example, an average temperature increase of 10 degrees C (18 degrees F) may more than halve the useful life of an electronic component when calculated using the techniques given in MIL-HDBK-217F (Reliability Prediction of Electronic Equipment).

Mitigating Heat Energy efficiency is first and foremost a measure that can be employed to take on the challenges; this tackles the heat release at its source. Optimizing rolling stock and traction power specifications, train speed operating profiles, and maximizing regenerative braking1 receptivity all play a major role in reducing temperatures, as well as reducing energy usage. For example, it might be preferable to provide more motored axles on the train to allow more regenerative braking (the number of motored axles might otherwise be rated on acceleration requirements alone). Such energy efficiency was an important part of the scope of work for London Underground where Parsons Brinckerhoff played a key role in the optimisation of

Regenerative braking is when the train motors are used to slow the train down. When they work in this way the motors act as generators, providing energy back to the traction power system for use by other trains. Without this technology the braking energy would be released as heat.

1

the cooling and traction energy demands for the recent Victoria Line upgrade. This was part of a suite of three London Underground projects that recently won the Institute of Civil Engineers 2014, Greatest Contribution to London Award.

Where mechanical cooling is required, natural water sources may offer significant energy savings. The use of groundwater in tunnel cooling systems can be traced back to New York City’s Brooklyn Bridge subway station in 1906, and it is still viable today. The technology has recently been successfully delivered by London Underground at Green Park station where Parsons Brinckerhoff provided engineering support across a range of disciplines. The Green Park system uses a submersible pump located approximately 60 metres (197 feet) below ground to extract 25 litres (6.6 US gallons) per second of water from an aquifer below London. The water is naturally at 13 degrees C (55 degrees F) and is pumped through a heat exchanger belonging to the main station cooling system. The borehole water is warmed by about 8 degrees C (14.4 degrees F) before being re-injected back into the aquifer via re-injection wells (see Figures 1 and 2). Note that Figure 2 shows only the wellhead chamber, the borehole is about 450mm diameter and starts at the base of the wellhead chamber. The main cooling system uses a secondary water circuit with air handling units (a cooling coil and fan) located at the platform level of the Green Park station (see Figure 3). The system successfully cools the station and tunnels and was awarded the first prize in the Environmental and Sustainability category for the 2013

Figure 1 - Borehole locations and pipe routes near Green Park station

Figure 2 - Borehole wellhead near Green Park station.

Figure 3 - Air handling unit delivering 100 kW of cooling to the platform of Green Park station

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When practicable traction energy optimisation methods have been adopted, the next logical step is the provision of cooling. For new systems, measures such as platform edge doors, air-tempering of platforms, and night time cooling may be used. For existing systems it can be significantly more challenging. Sustainable methods can be evaluated as a first alternative. For example, underplatform or over-track exhaust provides air extraction points near the heat sources, allowing the heat to be taken away in the ventilation ducts before it influences conditions in the station or tunnel. For the Victoria Line upgrade it was possible to upgrade 13 existing mid-tunnel ventilation shafts. This, however, generated challenges in mitigating the noise from the larger fan shafts that are now surrounded by dwellings and offices. In hotter climates, ventilation might be inadvisable on hot days and mechanical cooling may be preferred.

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Figure 4 - Thermal analysis of the heat recovery potential for pipework embedded into a 300mm tunnel liner with a soil depth of 20m

UK Rail Industry Awards. Parsons Brinckerhoff is reviewing the potential application of this technique to one of the High Speed 2 railway stations. Note that borehole cooling is just one of the techniques being used by London Underground; numerous other mitigations, including ventilation shaft upgrades and the use of mechanical cooling via air cooled chillers have recently been implemented.

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Sustainability may be further improved by heat recovery. For example, a heat exchanger in the tunnel may capture the heat from the tunnel, and a water circuit transfers the heat to the heat-sink side of a heat pump. The heat-source side of the heat pump may be connected to a third party’s building or small-scale district heating system, again by a water circuit, and provided with monitoring systems to record the amount of heat captured and utilised. Capturing the heat from the tunnel in a cost-effective manner remains a key challenge. Parsons Brinckerhoff has been involved in the investigation of several technologies including tunnel cooling pipes2, pipework embedded within the tunnel liner (see Figure 4), and the location of air source heat pumps in exhaust air plenums. For High Speed 2 we have developed a finite difference model of tunnel wall heat transfer and airflow within the tunnel (called Dynamo, see article in this issue on Dynamo by Jolyon Thompson) and are looking at the most cost effective way to re-use the heat from these tunnels.

Building the Case One of Parsons Brinckerhoff’s key roles on railway projects is the modelling and financial appraisals of cooling demands and cooling schemes. Typical methods include multi-train simulation to understand and optimize train energy usage, often done in conjunction with tunnel ventilation modelling. We have industry-leading tools for the evaluation of transient thermal comfort, and have developed methods in which changes in thermal conditions can be mapped to customers’ willingness to pay.

A Sustainable Outcome Sustainability is a key factor in railway cooling, and in the broadest possible sense. Social sustainability can be enhanced by providing the temperature control to support railway capacity upgrades that improve the quality of life for transit users and city dwellers. Environmental sustainability can be enhanced by reducing heat release in the railway through increased energy efficiency and low energy cooling methods such as groundwater cooling systems. Economic sustainability can be enhanced by optimising the cooling provisions and customer benefits to minimize whole-life costs with a demonstrable benefit to cost ratio. Parsons Brinckerhoff has an enviable track record in balancing these sustainability needs. Mark Gilbey is EAME Head of Discipline for Tunnel Ventilation. He is a Mechanical Engineer and has worked for Parsons Brinckerhoff since 1998 in Hong Kong, US, and the UK.

For the abstract of a previous article by Ting, Drake, and Gilbey on “CFD Estimation of Heat Transfer Enhancement on a Cooling Pipe in Underground Railway Tunnels,” see Network #70, November 2009, p 42.

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Dynamo – Enhancing Tunnel Ventilation Modelling by Jolyon Thompson, Godalming, UK, +44 (0)1483 528666, [email protected]

The Subway Environment Simulation (SES) software program was co-developed by Parsons Brinckerhoff for the US Department of Transportation in the 1970s. It allows engineers to mathematically model aspects of the subway environment on a second-by-second basis and continues to be regarded as an industry standard tool in the field of tunnel ventilation. SES is used worldwide for a variety of underground construction and tunnel applications, including high speed rail, commuter rail, metros, freight tunnels, road tunnels, and cable tunnels. A supplement to the SES has been developed by Parsons Brinckerhoff to enhance the capabilities of SES and to meet specific requirements of other tunnel system projects. This supplement is called Dynamo. Dynamo is a one-dimensional (1-D) model of a single length of tunnel which can simulate the effects of a ventilation shaft connected at any point along the length of the tunnel. Dynamo predicts the thermofluid interactions

using a variety of boundary and initial conditions which can be specified at each tunnel portal. Dynamo has been developed for use in tunnel ventilation and, as such, all relevant properties of air are encoded into the analysis engine. However, the Dynamo approach would work for any Newtonian fluid1 providing the relevant fluid parameters were input to the model. Dynamo has been used by Parsons Brinckerhoff on projects, two of which are described below.

Cable Tunnel Design A recent project consisted of an 18 kilometre (11-mile) long cable tunnel carrying 132kV cables beneath a natural bay. The cable circuits emitted a considerable amount of heat (over 800 watts per metre of tunnel length). The tunnels must be kept cool enough to limit the conductor temperatures in the cable and provide a safe environment for maintenance workers.

DYNAMO Parsons Brinckerhoff created a calculation tool to estimate the annual temperatures of long tunnels and with the ability to calculate the heat transfer from heat recovery mechanisms such as embedded liners and tunnel cooling pipes. The tool is named Dynamo. Dynamo uses a similar set of modelling assumptions to SES and therefore a single Dynamo file can and may need to take input from several SES simulations to account for variations in fan, train operations, or other significant variations in the system. The most significant difference is in the treatment of the deep heat sink effect through the surrounding soil. Dynamo uses a fully transient finite difference approach to allow thermal evolutions to be calculated in response to the tunnel environment, allowing complete year profiles to be developed. Dynamo uses an energy balance approach to determine the thermofluid interactions. The energy balance is at the core of the flexible Dynamo methodology. Any technology or system which can be formulated into an energy effect upon the system (input, output, or storage) can be included. Dynamo is a modular program which enables additional functions to be easily added and tested. All that the function requires is to be formulated to add to the energy balance in the correct manner. Examples of technology systems that have been added in this manner include cooling pipes and embedded tunnel liners. A Newtonian fluid is any fluid that exhibits a viscosity that remains constant regardless of any external stress that is placed upon it. This could include mixing or a sudden application of force. A Newtonian fluid can change viscosity if the temperature or pressure changes. The fluid would still be regarded as Newtonian providing the viscosity remained constant at these new temperatures or pressures.

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Due to the length of the tunnel, considerable airflow would be needed to prevent the air from becoming too hot. It was initially proposed to divide the tunnel into short sections and construct artificial islands within the bay which would provide ventilation inlets and outlets. However, this design would be expensive and could negatively impact the marine environment. An analysis of a cooling pipe system was therefore considered necessary.

nel for summertime peak hours only. Dynamo provided an hourly temperature prediction along the length of the tunnel for the whole-year. The temperatures predicted by Dynamo for both a ventilation only situation and the ventilation cooling pipe solution can be seen in Figure 1 and Figure 2. The x-axis (horizontal) shows the length along the tunnel and the y-axis (vertical) shows the time of year (summer being in the middle of the y-axis).

Previously a two-stage approach using an initial SES simulation supplemented with an Excel calculation sheet would be used. This required iteration between the two models to get the final result. If the cooling pipes loop and return to the portal-based cooling plants, this would result in a circular formula within the Excel analysis. The calculation therefore required a macro to control the process. The system was then iterated to ensure the accuracy of the calculation. The calculation process was thus bespoke to the situation and would need adjusting before it could be used with another tunnel layout option and it also took several days to complete.

The summer peak hours predicted by Dynamo compared very well with those predicted by the combination of SES and the Excel spreadsheets. The reduced time to set up the Dynamo simulations allowed for more options to be considered to optimise the cooling pipe design by comparing different water flow temperatures and pipe arrangements. This resulted in improved economic and environmental sustainability for the final design. The use of Dynamo also allowed for whole-year temperature predictions to be made, allowing annual system energy usage to be evaluated for each of the options and providing more accurate whole-life costing to be used in the design. This is an increasingly important facet of delivering sustainable design and represents a significant improvement in Parsons Brinckerhoff’s predictive capability.

Dynamo, in contrast, can be set up to evaluate the system in an integrated way. Since the only source of air flow is that generated by the fan against a constant resistance, the ventilation rate is also constant. The Dynamo analysis took less than four hours to set up, check, and simulate.

Dynamo for Waste Heat Recovery Dynamo can also be used to enhance the capabilities of SES in the analysis of recovery of waste heat from railway tunnels. This is an area which has received increased attention in recent years but is one which SES alone is not able to directly analyse.

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energy usage for nearby properties and developments. Dynamo was used to analyse the impact of using cooling pipes and embedded liners as the means of cooling the tunnel and for waste heat recovery. The heat and flow rate predictions from SES were used in the Dynamo analysis and similar temperatures for the summer peak hours were predicted. The cooling systems were then added into the Dynamo file and an assessment was made of the tunnel temperature reduction and the available temperature for heat recovery. The results of the tunnel temperature predictions can be seen in Figure 3.

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In a recent project, a 13.5 kilometre (8-mile) long highspeed rail tunnel was analysed using SES and predicted to be at a significantly elevated temperature over a substantial length of the tunnel during summer. To allow the tunnel to meet the design criteria, a cooling system was proposed and designed with a total peak cooling capacity of approximately 4MW.

Figure 3 - Annual tunnel temperature predictions before heat recovery

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The heat recovery system used a cooling pipe system that operates with a water flow rate of 70 kilograms per second (kg/s) supplied at 15°C (59°F) in 200 millimetre nominal diameter pipes. These cooling pipes are in the form of two loops which originate from chainage 10.7km and operate in opposite directions. Heat recovery may not always be considered as a method of reducing tunnel air temperatures appreciably despite producing significant benefits to other systems. The chart shows that heat recovery provided a minor tunnel temperature reduction of approximately 1.5°C (approximately 3°F), but an impressive 1500kW of heat from the tunnel environment as an annual average. The heat recovery from the tunnel can then be matched to the demands of a local area. In this case, illustrative demand profiles are shown in Figure 4. Dynamo enables the load profile variations to be accurately established and therefore matched to the demand profiles. Where the variations are in keeping with the available heat it is a relatively simple linkage between the heat source (the tunnel) and the heat sink (the heat load profile). Where there is significant variation, which is usual, the base level loading can be established and

any supplementary load requirements can be included in the design of the heat network.

Conclusion Two examples of Dynamo usage have been provided in this article. Dynamo has been shown to be capable of supplementing SES predictions in some areas which enhances the analysis capabilities of Parsons Brinckerhoff. References • Subway Environmental Simulation User Manual, 2003, prepared for the U.S. Dept. of Transportation • Thompson J.A., Missenden J.F., Gilbey M.J. and Maidment G.G., Response of wall heat transfer to steady and transient flows along a cylindrical cavity, Int. Symp. Aero. & Vent. Vehicle Tunnels, New Brunswick 2009 Jolyon Thompson is a Senior Tunnel Engineer in the UK office with a PhD in sustainable cooling of underground railways. He has a keen interest in heat recovery and improving the sustainability of tunnels through holistic design and was the lead developer of the DYNAMO analysis tool.

Asset Management Database for the Brooklyn Battery Tunnel by Ferdinand Portuguez, New York, NY, US, +1- 212-631-3891, [email protected]; and Debra Moolin, New York, NY, US, +1- 212-465-5443, [email protected]

Facility Description The Brooklyn Battery Tunnel (see Figure 1) crosses New York Harbor, connecting Brooklyn and lower Manhattan. The tunnel consists of two adjacent tubes, the east and west tubes, each approximately 9,000 feet long making it the longest continuous underwater vehicular tunnel in North America. Construction of the tunnel began in the 1940s but was suspended during the Second World War. The tunnel was opened to traffic on May 25, 1950 and now carries over 50,000 vehicles per day.

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Figure 1 - Brooklyn Battery Tunnel

The database for the Brooklyn Battery Tunnel (BBT), now officially known as the Hugh L. Carey Tunnel, is the key tool in the management of the various facility assets – the tunnel and four major building systems. The database was developed by Parsons Brinckerhoff in collaboration with the client, MTA Bridges and Tunnels, in 2012 with the objective of maintaining the facility in a “state of good repair”. Assets included in the database are: • Tunnel tubes, crossover passages, and construction shafts; • Manhattan Blower Building; • Manhattan Underground Exhaust Building; • Governors Island Ventilation Building, pedestrian bridge, fender structure, and riprap; • Brooklyn Ventilation Building; • Brooklyn Service Building and parking structure; • Manhattan Plaza, portal, and cellular structure; • Manhattan Plaza Emergency Garage; • Brooklyn Plaza and portal; and • Streets ancillary to the Brooklyn and Manhattan plazas.

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The database was populated with inventory information for each facility asset. Existing documents, reports, and construction plans were reviewed by Parsons Brinckerhoff before the start of the inventory inspection. Information on deficiencies and functionality of the mechanical and electrical systems were collected during interviews with maintenance staff, conducted by Parsons Brinckerhoff, and incorporated into the database. An overall condition rating of the electrical and mechanical systems was assigned based on this information.

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The database includes structural, architectural, mechanical, and electrical components – this article is focused on the tunnel systems which include:

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NETWORK Database Architecture The database of tunnel tubes and plazas includes an inventory of 65 different structural, mechanical, and electrical element types. These element types were inventoried by location with over 23,000 uniquely identified database elements or “entries” resulting. The database identifies over 150 element types housed in the buildings. These elements are defined by: • Asset – Identifies tube, plaza, building, or pedestrian bridge; • Discipline – Structural, Mechanical, Electrical, or Architectural; • System – Various tunnel and building systems; and • Location - Tubes - subdivided by wall marker stationing; then Construction Type - cut and cover steel bent, cut and cover concrete, light cast iron ring, heavy cast iron ring; and then Level - exhaust duct, roadway, fresh air duct; - Plazas - subdivided by expansion joints; - Buildings - subdivided by floor/(sub) levels; and - Pedestrian Bridge - subdivided by bents. See Figure 2 for a sample listing of element types. The comprehensive database also provides the following: • Identification of element-level electrical and mechanical deficiency types for use in future inspections; • Identification of element level deficiencies observed during the 2012 inspection with links to photographs of conditions; • The ability to sort and search the data within the database to facilitate condition management and reporting; • The ability to summarize condition ratings, deficiency types, and quantities of deficiencies; • Installation year, age, and expected service life – Parsons Brinckerhoff worked with the TBTA, to identify the estimated service life. Data from Federal Transit Administration (FTA) ‘assumptions regarding useful life for effective cost comparisons’ was considered as well

Figure 2 - Sample listing of element types

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as data being used for the Queens Midtown Tunnel inventory; and • System Element Condition Rating – Each system element includes a condition rating from 1: Continue in-service (Satisfactory Condition) to 4: Remove from service (Unsatisfactory – High Priority).

Database Worksheets The database was developed in coordination with the client using Microsoft Office Excel 2007. This format was chosen in order to create an asset management tool that is commonly understood by the engineering staff that would be working with the system. The Excel spreadsheets provide ease in the creation and manipulation of the large amount of data through simple functions such as sorting and filtering, and provide the ability to produce reports summarizing filtered and sorted data through pivot tables. Different groups of worksheets make up the Brooklyn Battery Tunnel’s database: • Support/Reference worksheets; • Master-Administrator Only worksheet; • End-User Database worksheets; • Database Expansion worksheets; and • Summary worksheet(s). Support/Reference worksheets These worksheets are the source of defined and known information contained in the Master-Administrator Only worksheets. These include: a summary of the repair/ rehabilitation projects and the coding used to define the element level that is inventoried and rated, along with the deficiency types applicable to each element. The Support/Reference worksheets standardize the terminology throughout the databases and minimize manual work during database updates by simplifying the steps for modifying or expanding the current range of data in the databases. The vast majority of the current

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Figure 3 - Identified elements for the tunnel ventilation system

information included in the Master-Administrator Only worksheet comes from the support worksheets through equations and links. The identified elements for the Tunnel Ventilation System within the tunnel worksheets are shown in Figure 3. Master-Administrator Only worksheet The Master-Administrator worksheet contains all the original data from the inventory and condition inspection. This worksheet is locked and can only be manipulated by users with necessary rights and passwords. End-User Database worksheets The End-User Database worksheets include a Filter worksheet and a Pivot Table worksheet and are intended to be used for queries, data access, sorting,

filtering, and reporting without working directly in the database spreadsheet. The data is therefore protected from inadvertent changes while sorting and filtering are being performed. The Filter worksheet is set-up with Microsoft Excel tools to filter specific data by area, regions, stations, element(s), and element ratings and/or deficiencies. This worksheet includes a sum of the quantity column and average of the rating column. This is also a dynamic calculation and provides the values for the elements that are visible during the filtering process. As an example, to manage the elements associated with the tunnel fireline, such as the fire hose valves and gate valves, the worksheet can be filtered as shown in Figure 4. The Pivot Table worksheet allows users to extract specific data from the databases by turning on specific columns from the master database and then filtering them to specific values. In contrast to the Filter worksheet, the Pivot Table allows for more specific extractions of data and allows users to display and print only the columns and rows that are needed (see Figure 5). On the right hand side, the “Pivot Table Field List” lists all the columns that are referenced from the Master-Administrator Only worksheet. As part of the tunnel drainage system, pumps are located in the Brooklyn Portal Pump Station, the Manhattan Blower Building, and the Governors Island Ventilation Building. A query of the tunnel drainage system housed on the Brooklyn side would result as shown in Figure 5. Database Expansion worksheets The ‘New Element’ tabs within the tunnel and buildings database workbooks are intended for use only when adding

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Figure 4 - Filter worksheet with elements associated with the tunnel fireline

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Figure 5 - Pivot Table worksheet showing query of the tunnel drainage system

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new elements to the Master-Administrator Only worksheet. This allows the database to be expanded to include new items that are added as part of the facility’s updates.

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Summary worksheets These worksheets are provided for the tunnel systems and sum each element’s total quantity and the element’s quantity per rating value, and quantity per deficiency type. The east and west tubes of the Brooklyn Battery Tunnel are tallied separately. Therefore the condition rating of various tunnel elements can be reviewed per query.

Conclusion The asset management database is an essential tool that can be used on a day-to-day basis or when scheduling and budgeting projects that will maintain the facility in a “state of good repair”. Within the database there are several worksheets that can be used to manage the various assets. Some are better suited for reports while other worksheets are better suited for obtaining data for monitoring the asset condition. Each worksheet aids in obtaining the necessary data, in the desired format, to make an informed decision.

During the aftermath of Superstorm Sandy, the database was used to determine replacement quantities for items damaged in submerged sections of the tubes (water filled approximately 6,000 feet of the 9,000 foot-long tunnel) and in the flooded sublevels of the buildings, and to obtain pertinent sump pump information. Its use during the operational response to that storm in 2012 contributed to the east tube reopening to limited bus service after 13 days and the west tube soon afterwards.

Ferdinand Portuguez is a Supervising Engineer with 22 years of experience in structural design, construction management, condition inspections, and cost estimating and assessment. He has a structural background and is a registered PE in New York State. Debra Moolin is a Structural Engineer (PE) with over 30 years of experience and a focus on bridge and tunnel repair and rehabilitation. She has worked on all project phases, from inspection, evaluation, and testing through design and construction support services.

SCADA System Security for Two UK Road Tunnels by Peter Massheder, Manchester, UK, +44 (0) 161 2005 015, [email protected]

Parsons Brinckerhoff is providing technical support to our client in specifying and procuring a new SCADA (supervisory control and data acquisition) system and associated equipment to replace seven obsolete control systems in use at two UK road tunnels. One tunnel was opened in the 1930s the other in the 1970s.

• Progressively expand and upgrade what is monitored in order to deliver improved visibility of the tunnels’ operational status; and • Move toward a decision support environment where incidents are detected and responses identified to the operator, simplifying the resultant control actions.

The project seeks to unify currently isolated tunnel control functions into a single SCADA interface, thereby reducing the number of separate control systems the tunnel operators have to access. Modern SCADA is no longer separated from other systems and only used by those who supervise the process under control. It is a system that collects an increasing array of data from increasingly ‘smart’ equipment and provides greater levels of analysis or access to this data by users whose principle roles are business-related, such as forecasting, billing, asset management, or planning.

Having defined this approach with the client and procured the services of a SCADA system integrator, we are now at the beginning of the journey to realize this vision, and to face and meet the challenges of delivering the programme and achieving the client’s objectives.

• Introduce a new SCADA platform and new programmable logic controllers (PLCs) which will communicate via the client’s converged Ethernet network; • Initially connect SCADA to existing mechanical and electrical equipment in both tunnels for tunnel environmental control (ventilation, lighting, dewatering, etc.); • Expand the system at a later date to connect to new traffic management equipment (signage, barriers, etc.) that is planned; • Latterly expand to take control of the emergency refuge areas installed in the 1930s tunnel, a four-lane single bore tunnel; • Interface with other tunnel management systems, such as the automatic incident detection system, in order to deliver improved connectivity to the operation of the tunnels;

Challenges The client’s primary objective is to ensure the safe and secure operation of the tunnels. Whilst a multitude of factors play a part in this, the security of the new control system is an important element and the requirement that the new SCADA and PLCs migrate onto the client’s converged Ethernet network becomes relevant. This network has both operational uses (the management of road tunnels and bus, rail, and ferry terminals) and business uses (office and enterprise IT for staff). Therefore a traditional separation and isolation of the control system is not straightforward. The challenge is specifying security requirements at the outset. This needs to happen ahead of the design work that will identify how the control system is integrated on the converged network, and these requirements will need to remain relevant as the control system is upgraded over the next four years. Equally, whilst the SCADA system integrator will hold overall responsibility for the SCADA system design, the client - through its IT department – will be involved in the design and delivery of the communications, server, and workstation environment. Here there is a need to ensure that a secure system can be implemented and to identify which party will be responsible for delivering the various elements of this. Our solution to this challenge has been to specify, within the SCADA system technical specification, adher-

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The method of project delivery presents the challenge here. In order to avoid disruption to tunnel users and at the same time align the SCADA works to a wider programme of tunnel maintenance and upgrade work, a four-year SCADA programme was developed by Parsons Brinckerhoff in collaboration with the client. This programme will:

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NETWORK ence to two international standards, ISO/IEC 27000 and IEC 62443.

Application of Cybersecurity Standards Cybersecurity standards have been created because sensitive information is now often stored on networked computers. This holds the potential for unauthorised access from within an organisation’s network or even via the Internet. With the greater integration of SCADA with other computer systems there is also a heightened risk that unauthorised access and manipulation of the process under control could occur; therefore, there is a need for information assurance and security. ISO/IEC 27000: Information Technology – Security Techniques was published some time ago and is generally applied by organisations to help define a security management system for their enterprise information systems. However, this standard does not consider the specific requirements of a time-critical control system and, whilst relevant to the wider security context in which the SCADA system will reside, we need something more to shape the design. This is where IEC 62443 comes in. IEC 62443: Industrial Communication Networks – Network and System Security is an emerging series of standards with parts still under development. The scope of the standards is specific to defining procedures for implementing electronically secure ‘industrial automation and control systems’. This guidance applies to end-users (i.e., asset owners), system integrators, security practitioners, and control systems manufacturers responsible for manufacturing, designing, implementing, or managing industrial automation and control systems. Whilst some parts are yet to be completed, what is published defines enough of a relevant approach to control system security to make its adoption beneficial. This recognises that during the four-year programme of SCADA work, the IEC 624443 series of standards will mature and its adoption at the outset, a strategic move, will ensure future SCADA system upgrades are able to build upon sound foundations. Further, the series is designed to build upon the guidance of ISO/IEC 27000 series and expands on ISA-99: Industrial Automation and Control Systems Security, a standard published by the International Society for Automation that has been in use and evolving for a number of years now. In summary we have judged that, whilst not yet complete, the IEC 62443 standard is mature enough to adopt.

Conclusion Work on implementing the SCADA programme is now underway. It is at the initial concept design stage and the high-level design necessary for the full SCADA system as envisioned is being explored. To this end the application of the IEC 62443 standard is coming into play. Although experience applying the standard across all parties is still in its infancy, we are learning valuable lessons as we go. For example, one such lesson is what we are calling our ‘levelling layers into zones lesson’. This lesson, put simply, is to ensure that there is a mutual understanding and use of terminology among all stakeholders. This is a common lesson in collaborative work and in this case is not one that reflects negatively on the standard itself, which is well constructed and clear. Rather the distinct uses of relatively interchangeable words such as ‘level’, ‘layer’, and ‘zone’ within the specification are recognised and highlighted for the stakeholders. Whilst seemingly a minor point, the current design work needs to ‘correctly’ define a logical segmentation of the control system in order to build defence in depth1 (in this instance, segmenting the system into zones within the operational level, a level that corresponds to layers 0 to 4 of the standard’s reference model – you see the potential for confusion if words are interchanged when communicating). To conclude, where other security guidance gives equally valuable insight into good practice, the IEC 62443 series of standards also helps in the development of a security management system that meets the needs of a SCADA control system. Further, as the standards build on guidance of ISO/IEC 27000 the resulting security approach may integrate better with an organisation’s information security management system, helping an organisation’s IT and automation control functions to more effectively collaborate on securing a SCADA control system. Whilst the full suite of the IEC 62443 series of standards is not yet complete and its application is in its infancy, we are seeing that this standard does form a valuable point of reference on security when specifying, developing, and ultimately maintaining a tunnel SCADA control system. Peter Massheder is a Principal Engineer with 26 years of experience in delivering automation, computing, and ecommerce solutions to clients across the utilities, transport, environment, and banking sectors.

Defence in depth is a concept in which multiple layers of security controls are built into an information technology system rather than relying on a single layer of security control. Its purpose is to provide more than one line of defence in case any one layer fails.

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CCTV Design for a US Road Tunnel by Ryan Williams, New York, NY, US, +1-212-631-3875, [email protected]

Safety is always the main factor for tunnel operation and control systems. Roadway tunnels are closed environments that must be monitored and controlled for the safety of vehicle occupants and tunnel personnel. The restrictive nature of tunnels, compared to open routes, makes it extremely hard to remove disabled vehicles and to evacuate or rescue accident victims. Congestion and incidents such as breakdowns, fire, or above-limit carbon monoxide (CO) levels must be detected and dealt with in a timely manner and the most effective way for operators within the control room to monitor the safe operation of the tunnel is via the tunnel’s closed-circuit television (CCTV) system. In addition to verifying roadway incidents, monitoring current traffic conditions, and fire and smoke detection, CCTV systems can be used for security surveillance of the tunnel facility and fire control zones. CCTV cameras are the main traffic monitoring devices for highway and transportation systems.

caused by the passing of heavy vehicles. Since vibration can negatively affect devices and their connections, hardened enclosures should be considered. Prior to commencing detailed design of the new CCTV system, the following design criteria needed to be addressed: • Coverage (including sensor type, lenses, aspect ratio, and camera angles); • Mounting; and • Communication System.

Coverage It is extremely important to identify the right locations for CCTV cameras and associated equipment panels. Cameras should be located to provide a clear line of sight with minimal obstructions. Tunnel cameras used in low light conditions should be located such that the main view is with the camera looking away from bright light. This is because video images in bright light taken from low light vantage points tend to appear washed out. Where changeable message signs (CMS) are installed, cameras should be located so that the message of an adjacent CMS can be read. This allows for visual verification of CMS status.

Parsons Brinckerhoff was engaged to design a new digital IP CCTV (internet protocol closed circuit television) system, replacing the existing analog system whilst maintaining the existing operation.

Large trucks and buses are moving obstructions to CCTV camera views. To overcome this obstruction issue, the design provided additional cameras with overlapping coverage to increase CCTV coverage. Overlapping cameras were also provided for curved tunnel sections and any other location with slower traffic movement. An option of using pan-tilt-zoom (PTZ) cameras was reviewed, which would give the operators additional functionality. This option was rejected, however, as it would introduce a risk of misaligning the cameras, and it would change the existing operational procedures in the control room.

The tunnel environment presents several challenges for proper design and implementation of CCTV, including humidity, dust, salt, and frequent vibration of equipment

In a CCTV system, the camera visualization options or functions for different types of applications or surveillance are measured by “pixels per foot”. A higher num-

The tunnel’s existing CCTV system is an analog system, with fixed cameras providing continuous views of the tunnel to tunnel operators in the control room. In other words, each camera provides a separate feed on a screen (four cameras per screen) in the control room.

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Parsons Brinckerhoff was engaged by a client to undertake remedial and resilience design work on a tunnel in the US that serves as an important thoroughfare for motor vehicles and was flooded in a storm.

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Figure 1 - Simulated view of camera coverage.

ber of pixels gives a higher resolution (e.g., in order to read license plates and recognize faces) and a lower number of pixels gives a lower resolution (e.g., to get a general idea of what is happening). The camera functions can be classified as: • Monitoring (a minimum requirement of 10 pixels per foot-vertical); • Object Detection (a minimum requirement of 20 pixels per foot); • Observation (a minimum requirement of 30 pixels per foot); • Recognition (a minimum requirement of 40-60 pixels per foot); • Identification (a minimum requirement of 60-80 pixels per foot); and • Strong Identification (a minimum requirement of 80100 pixels per foot). To fulfill the application requirements for the tunnel project, the Object Detection and Observation functions (a minimum of 20-30 pixels per foot) were designed to be maintained throughout the whole tunnel. Recognition and Identification functions were provided for some strategic locations. To verify full CCTV coverage, a CCTV simulation tool with three-dimensional (3D) view capability was used to assess coverage and provide simulated views at each of the proposed camera locations (see Figure 1).

Mounting Three camera mounting hardware mechanisms were analyzed for the tunnel installation: • wall-mounted hardware with short arm; • ceiling-mounted hardware; and • surface-mounted camera enclosure. Most camera manufactures have wall and ceiling hardware accessories but a surface camera enclosure would require a special order.

During the conceptual design, the possibility of mini camera integration to the lane-use sign (LUS) was also studied. This option would be an alternative to ceiling mounting and could provide better view angles as the lane-use signs are installed on the ceilings, above the road lanes. However, there are limited mini cameras available for such integration. This camera assembly also requires full integration of LUS and mini camera in NEMA 4X (IP 66/67) rated housing, which has limited space constraints. Three mounting options are described and depicted below: Wall-Mounted Figure 2 shows the arm and wallmounted option for the CCTV camera. The height of the camera may lead to obstructed views when large trucks and buses are in the tunnel. This location also poses a problem for maintenance, requiring the wash trucks to be Figure 2 - Typical Wall-Mount particularly careful around the fixtures. Despite the disadvantages, fixtures at this height would be easily installed and maintained. This mounting option also provides more selection of cameras. Ceiling-Mounted Figure 3 shows the ceiling-mounted dome camera option. This option provides adequate height for the camera to minimize the obstruction of views by large trucks or buses. The height also moves the camera out of the way of the maintenance trucks, but this type Figure 3 - Typical Ceiling-Mount of mounting could still be knocked loose and installation may be more difficult due to the height.

Communication System Migrating from an analog CCTV system to a digital IPbased system enables the tunnel controllers to gain a level of efficiency and control not previously available in overall operations. However, doing so requires a communication network to transmit the CCTV camera footage to the tunnel control center. On this project, various network types (star and ring topology) were considered based on ease of maintenance, redundancy, and resilience. A star topology is when each edge switch (switches in the field equipment panels) is connected to a central switch, typically in a control room. A ring topology is where each edge switch is connected to next and previous edge switch, forming a large ring. This option provides redundancy in that, if one of the switches were damaged, communication to downstream switches can be established through the other side of the ring. For the maintenance department, a star topology was preferred because it meant that all of the back-end equipment would be located in one central location. This means

that if something goes wrong, the maintenance personnel would only need to go to one place. It also means that if one part of the network goes down, it would not affect the resilience of the rest of the network. In an environment where it can be difficult to access and maintain network equipment, the operators can choose to leave a malfunctioning field switch out of service and not worry about a larger part of the network becoming inoperable if another fault occurs. It also means that there is a single point of failure at the core, control room switch (in the control room). That is, if the center of the star in the network went down, the whole network would be inoperable. To overcome the issues of a star network, a modified version of the star network was designed, with backbone switches installed in physically diverse locations (vent buildings and the control center) in a ring configuration and the edge switches (field switches) connected to each backbone switch in a star configuration. This provided the capability to operate the network from the vent buildings, in case the control center went down. Cybersecurity measures were implemented in Parsons Brinckerhoff’s design. Cybersecurity is an important component of all digital networks and requires diligent attention. It is not addressed in this article as it calls for much further discussion.

In Closing CCTV systems are integral to the safe operation and control of roadway tunnels. While CCTV technology can be fairly simple, the tunnel environment, maintenance, project requirements, and number of cameras can make the CCTV system design complex. This approach to CCTV system design is recommended for other projects to facilitate maintenance, whilst providing a robust system that can be verified through simulation prior to construction. Ryan Williams is a Senior Systems Engineer in our New York City office, having spent the last 8 years with Parsons Brinckerhoff in Australia. He is a registered professional engineer with chartered status and has substantial experience in transport and communication projects.

DECEMBER 2014 http://www.pbworld.com/news/publications.aspx

Surface-Mounted Enclosure Figure 4 shows the wallmounted dome camera option. The camera inside the dome enclosure is adjustable to the angle with an optimum view. This Camera option provides enough height to minimize view obstruction by large trucks and buses. The height also allows for easy installation. Finally, this type of mounting will result in minimal damage from maintenance and wash trucks, but limits camera selection options as few fixed cameras are manufactured with this mount. Figure 4 - Typical Surface-Mount

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How Alternating Current Interacts with Direct Current in the Shatin to Central Link Traction Systems in Hong Kong – A Quantitative Approach by Sam Pang, Hong Kong, +852-2963-7777, [email protected]

Background The Shatin to Central Link (SCL) is one of the ten largest infrastructure projects being constructed in Hong Kong. It is a 17 kilometre territory-wide strategic railway corridor with ten stations. The project is linked with a number of existing railways, forming two strategic railway corridors: the “East West Corridor” and the “North South Corridor” as shown in Figure 1. The “East West Corridor” is formed by the Ma On Shan Line (the proposed Tai Wai to Hung Hom Section of the SCL) and the existing West Rail Line. Upon completion, passengers will be able to travel between Tuen Mun in the west and Wu Kai Sha in the east without interchanging (transferring) trains.

DECEMBER 2014 http://www.pbworld.com/news/publications.aspx

Lok Ma Chau

Lo Wu

Along the SCL, there are three (3) underground stations where the SCL interchanges with the existing Urban Rail Lines (URL). They are: Diamond Hill Station (DIH), Ho Man Tin Station (HOM), and Admiralty Station (ADM). As the SCL will be electrified at 25kV alternating current (AC) while the existing URL is electrified at 1.5kV direct current (DC), AC and DC traction systems will coexist in these underground interchange stations (also referred to as “AC/ DC interchange stations” in this paper).

East West Corridor North South Corridor

Wu Kai Sha East Rail Line

Tuen Mun Tai Wai

West Rail Line

Ma On Shan Line

Diamond Hill Shatin to Central Link (Tai Wai to Hung Horn Section)

Hung Horn

Admiralty

Figure 1 - Alignment of the Shatin to Central Link

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The “North South Corridor” extends the existing East Rail Line across the harbor via Hung Hom. Upon completion, it will link the immigration control points at Lo Wu and Lok Ma Chau to Hong Kong’s central business district.

Shatin to Central Link (Hung Horn to Admiralty Section)

All interchange railway lines at Ho Man Tin Station and Admiralty Station are accommodated within the same station structure, whereas the existing Diamond Hill Station (DIH) station and the future DIH station of SCL (hereinafter referred to as “SCL-DIH”) are separate structures connected by an adit. With a common station structure, the earthing (grounding) systems at Ho Man Tin Station and Admiralty Station will essentially be bonded together. For DIH, there was an option in the design of bonding the earthing system of the existing and the future DIH station or introducing an isolation zone between the two station structures. Parsons Brinckerhoff was appointed by the MTR Corporation Limited to carry out the detailed design of the trackside auxiliaries of the SCL. As part of the design, Parsons Brinckerhoff carried out a detailed study on the risks associated with the coexistence of AC and DC traction systems in the interchange stations and established the earthing and bonding strategy to mitigate the risks.

At the time of carrying out the study, apart from a handful of papers on the subject of AC and DC railway interfaces and the European Standard EN50122-3:2010, there were very limited references on the subject of mutual interaction of AC and DC traction systems, in particular on its quantitative analysis. The Parsons Brinckerhoff project team approached the challenges from fundamental theories and developed quantitative analysis methods in order to establish the earthing and bonding strategy for the SCL to mitigate potential problems.

Problems of Mutual Interaction of AC and DC Traction Systems This section gives an overview of the potential issues associated with the mutual interaction of AC and DC traction systems. The AC traction system can affect the nearby DC traction system or vice versa by coupling, which is the physical process of transmission of energy. The effects of coupling can be galvanic and non-galvanic. The galvanic couplings refer to conductive voltages and currents. These occur when the AC traction system is connected or bonded to the DC traction system, in particular at the interchange stations. The major problem is that the DC currents in the DC traction system can flow into the AC traction system and return to the DC traction system through galvanic couplings. The DC currents when flowing through the AC train-borne transformers and AC traction transformers may cause saturation of the core of these transformers. Related studies indicate that a small DC bias can have the following consequences: complete saturation of the core with the generation of harmonics (distortion of signals); a very considerable reduction in the magnetising impedance of the transformer; internal electrical resonance in the transformer winding; increased noise level; increased no-load current and losses. Moreover, when the DC current flowing into the AC traction system returns through the metallic parts of the station structure, stray current corrosion will occur. The non-galvanic couplings are inductive and capacitive in nature. The effects of inductive coupling are induced voltages and currents. These voltages and currents depend on the distance, length, inducing current conductor arrangement, and frequency. The effects of capacitive coupling are induced voltages into a conductor. The induced voltages depend on the voltage of the influenced system, the distance, and the frequency.

Apart from the galvanic and non-galvanic couplings, the following operational issues associated with the design of power supply systems require particular attention in the dual electrified interchange stations: • Electric shock caused by 25kV flashover to common station metallic infrastructure and extraneous metal parts; • Voltages induced by the 25kV traction currents causing interferences to the signalling, communications, and low voltage circuits, or electric shock in the DC electrified railway; • Earth faults in the high tension side of the 25kV AC traction substation may lead to rise of earth potential and rail potential in the AC and DC traction systems; and • Increased AC traction current causing increased mutual couplings, and increased DC traction current causing higher stray current corrosion due to more frequent train service. This article focuses on the quantitative approach taken to analyse the effects of DC stray current corrosion at the underground interchange stations and DC traction currents flowing into the AC traction system.

DC Stray Current Corrosion at the Interchange Stations Figure 2 illustrates the flow paths of the DC traction currents and the voltage thus created at the station structure of an interchange station where AC and DC traction systems coexists. To review the degree of stray current corrosion at the interchange station, it can be reasonably assumed that adverse corrosion will occur at the point where the maximum DC stray current passes through. That should be the point within the interchange station that interfaces with the DC return. At this point of maximum stray current, the voltage with respect to earth is calculated and benchmarked with the reference value of +0.2V as specified in European Standard EN 50122-2:2010. According to clause 5.3 of EN50122-2:2010, experience has shown that there is no cause for concern if the average value of potential shift between the structure and earth in the peak traffic hour does not exceed +200mV for steel in concrete structure. To estimate the maximum voltage or the potential shift of the station structure and metallic parts in the interchange station, a DC equivalent circuit as illustrated in Figure 3 was constructed for the typical rail section as shown in Figure 4 with the circuit parameters given by

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Challenges

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DC OHL Network

DC FEEDER SUBSTATION DC RAIL NETWORK DIODE EARTH

STRAY CURRENT

STRAY CURRENT

DC STRAY CURRENT RETURN PATHS

MAXIMUM VOLTAGE FOR STRAY CURRENT AT AC/DC INTERCHANGED STATION

CONNECT TO STATION STRUCTURE AND OTHER METALLIC PARTS

DECEMBER 2014 http://www.pbworld.com/news/publications.aspx

Figure 2 - Potential Created by Stray Current at the Interchange Station

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Figure 3 - DC Equivalent Circuit for Calculation of Potential Shift at Station Structure

the client and the train modelled as a current source of 4,000A. For a conservative analysis, the train positions that would give rise to higher stray current at the interchange stations were taken in the voltage calculations. With the equivalent circuit, calculations were then performed to estimate the maximum potential shift at the station structure of the three interchange stations for several

different train positions and rail-to-earth resistance (RTE). As as shown in Table 1, for DIH, ADM, and HOM, the results of the estimated maximum potential shift of the station structure are all below the +200mV criterion listed in clause 5.3 of the European Standard, suggesting that there would not be an adverse effect of stray current corrosion at the interchange stations. However, for better

Circuit A Train positioned at middle of rail section

Voltage (V)

0.25 0.2 0.15

Circuit B Train positioned at 250m from interchange station

0.1 0.05

-3.89E-15 0

0.24

0.48

0.72

0.96

1.44

1.2

1.68

1.92

2.16

2.4

Distance (km)

Figure 4 - Potential Shift vs. Train Positions with Rail-to-Earth Resistance Decayed to 15 ohm/km per track

Interchange station

Estimated Maximum Potential Shift at Station Structure (all at RTE1 = 15 ohm/km per track)

DIH

0.12 V (< 0.2V)

ADM

0.1 V (< 0.2V)

HOM

9.4 mV (