MELBOURNE METRO RAIL PROJECT
BUILDING THE TUNNELS
A range of construction techniques will be used to build the Melbourne Metro Rail Project, with an
emphasis on reducing impacts to local residents and the business community.
Overview
Melbourne Metro’s twin nine kilometre tunnels will take two of the busiest rail lines out of the City
Loop creating space for more trains to run more often across Melbourne.
The project will create a new end-to-end rail line from Sunbury in the west to Cranbourne / Pakenham
in the south-east and five new underground stations.
Feedback received during the planning process will inform the development of project designs and
construction strategies.
Building rail tunnels
Building Melbourne Metro presents a number of challenges, including:
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Managing disruption to residents, businesses and events
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Mitigating the impacts on road traffic, pedestrians, cyclists and existing public transport and
freight services
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Navigating existing underground infrastructure – including utilities, the City Loop and CityLink
tunnels
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Excavating through a range of geological conditions including rock, clay and silt
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Tunnelling under two significant waterways, the Yarra River and Moonee Ponds Creek
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Managing the logistical task of removing large amounts of excavated material
Site investigations at various locations along the proposed alignment are helping to understand the
existing geological conditions and confirm the location of underground services. This information will
also assist in determining the preferred construction methodology for different sections of the project.
Construction methods
A number of different construction techniques will need to be used to successfully deliver a project as
large and complex as Melbourne Metro.
Tunnel boring machines (TBMs) will be used to build the rail tunnels between most stations, with
mined tunnels likely to be built in the CBD. Excavation and earthmoving equipment will be used to
create the entrances to the tunnels and three new stations outside the CBD. To minimise the impacts
on Melbourne’s city centre, and specifically Swanston Street, mined cavern construction will be used
to build the CBD North and CBD South stations.
The proposed construction techniques have been used to build many underground rail projects
around the world and are tried and tested under a range of conditions.
The Melbourne Metro Rail Authority will work with our contractors (once appointed) to identify ways to
reduce the unavoidable construction impacts of the work required.
Mined cavern construction
It is proposed to use a technique known as mined cavern construction to build Melbourne Metro’s two
CBD stations.
Access shafts are dug from the surface to build the caverns, in this case on land adjacent to
Swanston Street where the station entrances will be. These shafts are then used to transport
machinery, equipment and workers underground to the station cavern. Multiple road headers are
used to excavate the station caverns under the surface of Swanston Street.
This engineering technique will minimise disruption at surface level and is commonly used overseas,
particularly in constrained city environments. Under this solution, trams will continue to run up and
down Swanston Street during construction and the above ground disruption to businesses, cyclists,
pedestrians and cross streets will be greatly reduced.
Cut and cover
The new Arden, Parkville and Domain stations and the entrances to the tunnels will likely be built
using a construction technique known as cut and cover.As the name suggests, this type of
construction involves using excavation equipment to dig a large trench or rectangular hole in the
ground which is then covered by a concrete deck. Once the deck is in place, surface activity can
largely resume as construction works continue below.
During construction of the stations, poured concrete or pre-cast panels are used to form the various
levels and internal structures, similar to the construction of the underground basements of high rise
buildings.
Connecting tunnels to the Sunbury and Cranbourne / Pakenham rail lines in Kensington and South
Yarra (known as portals) will use a similar approach, with excavation equipment used to dig a
descending trench from ground level to a depth where the Melbourne Metro tunnels begin.
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Tunnelling under the Yarra River
Melbourne Metro’s rail tunnels will also be constructed under the Yarra River, which is up to four
metres deep in this location. The top of the twin tunnels, each around seven metres in diameter, will
be around seven metres below the riverbed, east of the Princes Bridge.
To minimise impacts on the Yarra River and surrounding areas, tunnelling using TBMs has been
selected as the preferred method of construction for this section of the project. Other options
considered include an ‘immersed tube’ and a cofferdam construction method.
Tunnel Boring Machines
TBMs are large machines that tunnel through ground, progressively installing concrete linings to
support the excavated tunnel. The excavated material is transported through the machine to the
surface for removal by trucks.
TBMs are typically used in the construction of long underground tunnels. They are tailored for specific
conditions and can be several metres in diameter, more than 100 metres long and weigh up to 1,000
tonnes.
TBMs have been used to build Sydney Metro Northwest’s rail tunnels and London’s Crossrail tunnels.
How do they work?
TBMs have two main elements. The first part uses a rotating cutter head that excavates through the
ground and disposes of the excavated rock and soil via a conveyor belt that runs behind it. The
second part lines the tunnel with pre-cast concrete segments to support the ground and minimise
groundwater seepage into the tunnel.
At the start of the process, a large shaft is dug from ground level down to where the TBM needs to
start tunnelling. A launch chamber is then excavated, allowing the TBM to be lowered into the shaft in
sections and reassembled before it begins excavating towards a station or tunnel entrance. It is then
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moved through the station to begin excavating the next section of tunnel, or extracted at a station or
retrieval shaft and taken back to the launch site to start digging another section.
A number of TBM launch and retrieval shafts will be needed to support tunnelling activities for
Melbourne Metro.
The TBM launch site for the western section of the project will be located at Arden station and there is
a TBM retrieval site planned for the Western Portal (western tunnel entrance) area.
A number of TBM launch sites are being considered to support tunnelling activities in the eastern
section of the project. These options include part of St Kilda Road just to the north of the new Domain
station as well as a section of Fawkner Park near Toorak Road West. A TBM retrieval shaft is planned
at the Eastern Portal (eastern tunnel entrance) area.
A range of activities need to take place around the TBM launch shafts to support tunnelling
operations. These include office and site facilities, the processing and management of excavated
material prior to disposal, as well as storage of the concrete segments used to line the tunnels. There
will also be cranes installed to lower the TBM components into the shaft. A concrete plant within the
Arden station site will produce the concrete segments, which will be transported by road to the
eastern section of the project.
The TBMs to be used on Melbourne Metro can work up to 40 metres underground and will likely
operate around the clock.
Mined tunnels
Another method of tunnelling is proposed to excavate beneath Swanston Street to construct the new
Melbourne Metro tunnels between the two CBD stations.
Due to the expected ground conditions and the number of building basements and foundations in the
area, a mined tunnel is considered to be the most appropriate method of excavation.
The proposed mined tunnelling method uses road header machines to dig the tunnel. These
machines have a rotating cutter head that is mounted on a boom. After the road headers carve out
the tunnel, it is reinforced with a combination of rock bolts, lattice girders and sprayed concrete.
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Using this technique rather than ‘cut and cover’ reduces the impact of construction on the CBD, as the
tunnel between the two new CBD stations can be built completely below the road surface, meaning
trams, pedestrians and cyclists can continue to access the heart of the city.
Did you know?
TBMs cost around $20-$30 million each and can move between 300 and 360 metres a month,
depending on ground conditions.
The scale of Melbourne Metro means it needs to be supported by a number of construction sites.
Construction sites
These sites are currently proposed to be located at the station precincts or at other suitable locations
along the alignment. Using these sites may also require the protection, relocation, or in some cases,
the removal of trees. The Melbourne Metro Rail Authority (MMRA) is continuing to refine the
construction approach to determine the best way to reduce impacts on the surrounding parklands.
Western Portal (western tunnel entrance)
It is proposed to locate a construction support site in the industrial area between the Maribyrnong
River and Kensington Road. There will also be construction along Childers Street from Kensington
Road to Bakehouse Road. This may require the construction of a widened retaining wall as well as
the excavation of the tunnel entrance from the surface down to the level of the Melbourne Metro
tunnels. A temporary TBM retrieval shaft will also be built in industrial land near Bakehouse Road.
The track works at Kensington, to connect Melbourne Metro with the existing Sunbury rail line, will
require some temporary rail line closures to enable works to proceed safely.
Arden station
Arden station, located in industrial land in North Melbourne, will be used to launch TBMs, store
materials, manufacture the concrete segments that will be used to line the Melbourne Metro tunnels,
process and manage excavated material and support construction across the western parts of the
project.
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Parkville station
The construction site for Parkville station will extend along Grattan Street between Royal Parade and
Leicester Street and require Grattan Street at this location to be temporarily closed for an extended
period. Areas on top of the University Square car park, parts of Barry Street and along Elizabeth
Street may be temporarily occupied to support construction activities.
CBD North
Part of Franklin Street between Swanston and Victoria Streets may be temporarily occupied to
support construction of CBD North station, along with a site on the corner of La Trobe and Swanston
streets. Excavated material from the mined cavern construction of the station will be removed through
these sites.
CBD South
A number of sites are required to support the construction of CBD South station. City Square will be
temporarily occupied to facilitate construction of the station cavern, a station entrance and also act as
a material storage area.
There will also be a construction site facing onto both Swanston and Flinders streets (around, but not
including, the Young & Jackson Hotel). Another construction site will be located at the proposed
Federation Square entrance.
Linlithgow Avenue
A construction site will be required to build a small emergency access shaft near Linlithgow Avenue in
Queen Victoria Gardens or at an alternate site at nearby Tom’s Block.
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Domain Station
Part of St Kilda Road, to the north of Domain station, may be used as a TBM launch site. Additionally,
construction support sites for Domain station are proposed to be located on the Edmund Herring Oval
on Domain Road, in Albert Road and on edges of the Shrine of Remembrance grounds fronting St
Kilda Road and Domain Road.
Staged closures of St Kilda Road will allow for the excavation work for Domain station and enable
trams and traffic to keep moving. The temporary closure of Domain Road at St Kilda Road will require
trams to be re-routed down Toorak Road West for the duration of the works.
Fawkner Park
A section of Fawkner Park, facing Toorak Road West, could be temporarily used as a support site and
staging area for the project’s use of TBMs. In this event, MMRA would work closely with the City of
Melbourne and local residents to minimise the impacts on local amenity during these works.
A small structure would remain at this site following completion of the tunnel to provide emergency
services access to the Melbourne Metro tunnels.
Eastern Portal (eastern tunnel entrance)
The Eastern Portal site at the South Yarra Siding Reserve will be a construction site to support the
required works within the rail corridor to accommodate the Melbourne Metro tracks and as a TBM
retrieval site. The track works at South Yarra to connect Melbourne Metro with the existing
Cranbourne / Pakenham rail line will require some temporary rail line closures to enable works to
proceed safely.
Managing excavated material
More than 1.7 million cubic metres of excavated material - soil and rock - will be produced during the
construction of Melbourne Metro. This is expected to require more than 140,000 truck movements
from construction sites along the tunnel route during the tunnel and station construction process.
Acknowledging the importance of roads to local communities, effective traffic management plans will
be developed to manage this large number of truck movements. Traffic studies are currently being
completed to enable planning to minimise the impacts on Melbourne’s road network.
Construction hours
The timing of works on Melbourne Metro will be determined in consultation with the project
contractors, local councils and the EPA, and through the planning approvals process. Under certain
circumstances, above ground works may be needed after hours, and neighbouring residents and
businesses would be notified in advance of these works.
Underground tunnelling works are expected to generally occur 24 hours a day, seven days a week.
Construction sites that support tunnelling activities could also operate around the clock. Additionally, a
variety of noise-reducing structures including noise walls and acoustic sheds would be used at sites
required to operate 24 hours a day.
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How can I get involved?
Melbourne Metro is a project for all Victorians, and community members are encouraged to learn
more and provide feedback to the project team during the planning approvals process.
You can have your say by phone, email, post or via the project website (see contact details below).
Feedback received from the community and key stakeholders, along with technical and environmental
assessments, will be incorporated into the project’s Environment Effects Statement (EES).
Following the development of the EES, the public will be able to view planning documentation and
provide further feedback during the EES public exhibition phase in mid 2016.
Planning for Melbourne Metro
The Melbourne Metro Rail Project is being assessed through an Environment Effects Statement
(EES) process.
The EES for Melbourne Metro is assessing the environmental, social and planning impacts
associated with the project. This process is supported by a range of technical investigations that will
assess the project’s environmental, heritage, urban design traffic and transport, economic and social
impacts.
For more information see the Melbourne Metro Rail Project – Planning Approvals Process fact sheet.
Have your say
Please visit the following website to have your say about the Melbourne Metro Rail Project:
yoursay.mmrailproject.vic.gov.au
More information
To find out more about the Melbourne Metro Rail Project and register for future updates:
Website: mmrailproject.vic.gov.au
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Phone: 1800 551 927
Twitter: @mmrailproject
LinkedIn: https://www.linkedin.com/company/melbourne-metro-rail-authority-mmra
Postal address:
Melbourne Metro Rail Authority,
PO Box 4509, Melbourne, VIC 3001
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