INTRODUCTION: Global Perspectives on Tunnel Systems

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Image courtesy of Well-Connected Alliance

The needs of future tunnel owners, operators, and users, as well as developing tunnel systems that respond to those needs, are discussed on a global basis.

For decades, Parsons Brinckerhoff (now part of WSP | 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 co-developed 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, WSP | Parsons Brinckerhoff’s Hong Kong office was established. Over 40 years later in 2015, Dr. Norman Rhodes of WSP | Parsons Brinckerhoff chaired the 2015 16th International Symposium on Aerodynamics, Ventilation, & Fire in Tunnels to be held in Seattle, Washington. 

Advances in tunnel systems have evolved to account for a changing world, and WSP | 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). 

WSP | 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 programs such as the Memorial Tunnel Fire tests1 in West Virginia, led by WSP | 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, WSP | 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 built-in 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. WSP | 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 present and future. WSP | 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

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, WSP | 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 WSP | 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 U.S., 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 performance-based 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 U.S. 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. WSP | Parsons Brinckerhoff has continually developed and refined our 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. 

High speed rail projects frequently involve long tunnels and long distances between stations. WSP | 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

The U.K.’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 U.K. 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). 

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. WSP | 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 U.K.’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.

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 with the U.K.’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 WSP | 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 U.K., our team of engineers is at the forefront of innovation. 

WSP | Parsons Brinckerhoff continues to retain its high profile in tunnel systems capability through many of the major projects being undertaken. WSP | 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. 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 WSP | Parsons Brinckerhoff. 

Tunneling Overview in Asia 

by Steven Lai

WSP | 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, WSP | 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, WSP | 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. WSP | 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. WSP | 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. WSP | 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. WSP | 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. WSP | 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.) 

WSP | 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; 
  • 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.) 

New challenges in tunnel systems. Nowadays, exceptionally long tunnels with large cross-sectional areas and/or multi-purpose tunnels create new challenges to engineers. WSP | 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 meters (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. WSP | 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 tunnel 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, WSP | Parsons Brinckerhoff has designed and developed cost-effective 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, WSP | Parsons Brinckerhoff is the first company in Hong Kong to use building information modelling (BIM) for the tunnel systems of a road tunnel project. WSP | 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

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 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. 

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

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 Selection 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. WSP | 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 cost-effective design for both construction and maintenance. 

WSP | 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 WSP | 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 ventilation 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 tunnels. 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 WSP | 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. 

1See “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.

2NFPA 130 (2014) and NFPA 502 (2014), National Fire Protection Association,

3For 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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