The $13 billion Metro Tunnel is the biggest upgrade of Melbourne’s train network since the City Loop opened in 1981.

The Metro Tunnel will create a new end-to-end rail line from Sunbury in Melbourne’s west to Cranbourne and Pakenham in the south east, with bigger and better trains, next generation signalling technology and five new stations.

With its twin 9km tunnels, it will give passengers direct train access to new destinations including St Kilda Road (Anzac Station), Melbourne’s major health and education precinct (Parkville Station) and North Melbourne (Arden Station). Passengers will save up to 50 minutes a day on a return train trip, and there will be capacity for an extra half a million passengers across the network every week.

The Cross Yarra Partnership (CYP)—a joint venture between John Holland, Bouygues Construction Australia and Lendlease—is building the twin tunnels and five new stations.

In conjunction with fabricators Stilcon, GB Galvanizing undertook the galvanizing and installation of 50,000 brackets and 16km of elevated steel walkway for emergency and maintenance access between two of the new Metro Tunnel stations: Anzac Station (located at the intersection of St Kilda Road and Domain Road) and Arden Station in North Melbourne.

In total, GB Galvanizing hot dip galvanized over one million components—equivalent to approximately 1,600 tonne of steel—including:

• 1,000 tonnes of chequer plate
• 400 tonnes of mild steel plate
• 100 tonnes of 75PFC
• 90 tonnes of 100PFC
• 40 tonnes of 50x5EA

Commenced in July 2021, the Metro Tunnel is expected to open in 2025, a year ahead of schedule.

MARKET DEVELOPMENT POTENTIAL FOR THE INDUSTRY (30 POINTS MAX)

According to Vince Gucciardo (Operations Manager, GB Galvanizing), Galvanizing was the perfect solution for the internal structures of the Metro Tunnel Project. “This project demonstrates that not only is galvanizing is the most suitable anti-corrosive coating for infrastructure, it is also economical during construction and maintenance, fast to erect, and provides better damage resistance compared to paint.”

“While the use of galvanizing in infrastructure isn’t ground-breaking, the innovation in the Metro Tunnel Project lies in its modular design. This design was pivotal in ensuring that fabricators, transporters, galvanizers, and installers collaborated efficiently and safely. A hallmark of the project was the significant emphasis on communication among stakeholders. This wasn’t just crucial for the galvanizing aspect, but also for safe handling by all involved, setting a precedent for similar large-scale projects in the future,” said Gucciardo.

PERFECTING THE PROCESS

When it comes to large-scale infrastructure projects, innovation does not always involve reinventing the wheel, but rather refining it for efficiency, safety, and adaptability. In the Metro Tunnel Project, the technical approach to galvanizing embodied this principle—it was centred around practical adaptability and efficient processes.

“One of the challenges of the project was the shapes, sizes, and safe handling weights of the project components. The inherent flexibility in our design allowed brackets and support frames to adjust and fit the tunnel’s unique dimensions. A quick glance at the installed product’s photographs showcases this innovation: platforms with adjustable angles ensured perfect alignment and level surfaces. Moreover, keeping the components’ weights within manageable limits eliminated heavy-lifting equipment for many items, streamlining the installation process,” said Gucciardo.

During the design phase, detailed planning and discussions were essential given the tunnel’s limited access and the need to assemble components in situ over its 16km length.  Galvanized components could not be too heavy for people to handle; the brackets and smaller items had to remain under 20kg to 30kg each so that they could be lifted without a forklift.

“One of the primary challenges we faced was the stringent turnaround times. With over a million components, many of which needed individual hanging, the logistics were demanding. Handling plates required quick jig creation, and the sheer volume of components necessitated countless hours of hanging and cleaning,” said Gucciardo.

“Moreover, during certain periods, such as site shutdowns, managing storage space became particularly challenging. At one stage, we had 15 loads stored in our yard, all of which had to be kept separate. Ensuring components from different loads were kept distinct was another logistical concern.”

ECONOMICAL AND EFFICIENT

The use of hot dip galvanizing on the Metro Tunnel Project plays an instrumental role in achieving the economic benefits desired by the asset owner. These benefits stem from three key aspects: lower initial cost; reduced maintenance requirements; and efficiency in fabrication to installation.

Lower Initial Cost

When viewed against comparable coatings and paint solutions, hot dip galvanizing provides an economical alternative without compromising quality or durability.

For a project as vast and significant as the Metro Tunnel, this translates into substantial initial cost savings. The sheer volume – over 1,600 tonnes of steel and one million components – underscores the magnitude of cost efficiency achieved.

Reduced Maintenance Requirements

“In the challenging environment of a metro system, the long-term resistance to wear and tear delivered by galvanizing means a substantial reduction in ongoing maintenance costs—particularly important given that undertaking maintenance works on an operational train network is expensive and poses health and safety challenges for workers,” said Gucciardo.

Less maintenance not only translates into direct financial savings but also minimises service disruptions, delivering indirect economic benefits by optimising usability of the train network.

Efficiency in Fabrication to Installation

With a compressed delivery timeframe, Stilcon and GB Galvanizing were able to fabricate, galvanize and install all critical components between Anzac and Arden stations in line with the client needs. The efficient streamlining of this process played a key role in the Metro Tunnel’s anticipated early opening – a year ahead of schedule.

GREEN INNOVATION: METRO TUNNEL’S SUSTAINABLE BLUEPRINT

Sustainability is at the heart of the Metro Tunnel Project. For example, all five of the new stations boast 6-star Green Star design accreditation from the Green Building Council of Australia.

The expansive roof space at the new Arden Station has been used to install 125kW of solar panels – 392 panels in total. These solar panels will generate approximately 140MWh of electricity annually, enough to power about 50 homes. The renewable energy replaces 15% of grid electricity used by the station, and helps power lighting, ventilation, escalators and lifts. It is expected that use of renewable electricity at Arden Station will reduce carbon emissions by approximately 146 tonnes per year.

Given the emphasis on environmental sustainability throughout the design and construction of the Metro Tunnel, it is little wonder that galvanizing was specified. The long-term durability provided by galvanizing is achieved at a relatively low environmental burden in terms of energy and other globally relevant impacts, particularly when compared to the energy value of the steel it is protecting.

Project Team:

• Client: CYP Design & Construct JV (joint venture between John Holland Pty Ltd, Bouygues Construction Australia Pty Ltd and Lendlease Melbourne Metro Pty Ltd)
• Galvanizer: GB Galvanizing
• Fabricator: Stilcon
• Structural Engineer: TTW Structural Engineers
• Steel Suppliers: BlueScope and Infrabuild
• Steel Detailer: RMS Engineering Services
• Acoustics Works Contractor: Baron Forge