Construction techniques

The West Gate Tunnel Project uses various construction techniques and some of the biggest pieces of machinery in the southern hemisphere to build the twin tunnels under Yarraville and the elevated road above Footscray Road.

Elevated road builder

Another important part of the West Gate Tunnel Project is an elevated road above Footscray Road which links the tunnels to CityLink, Dynon Road and Wurundjeri Way.

It will also include direct connections to the Port of Melbourne for trucks.

The machine will continue west towards Footscray for 1.2km to build the outbound lanes before it changes direction to build the city-bound lanes. In total, the machine will travel 2.5km to build 6 new lanes.

Keeping Footscray Road open

The construction method means Footscray Road can stay open with less disruption for cyclists and motorists and maintains uninterrupted access to the port for our important freight and logistics industries.

  1. Concrete segments are transported to site.
  2. They are lifted piece by piece until a total of 17 segments are in place.
  3. Steel cables are threaded through the segments and tightened to form a span. Grout is then poured, encasing the steel cables to secure and strengthen the span.
  4. The machine then moves forward to make the next span.

Tunnel boring machines

We are building twin tunnels between the Maribyrnong River and the West Gate Freeway, providing a vital alternative to the West Gate Bridge. The project will ensure quicker and safer journeys and remove over 9000 trucks from streets in the inner west.

The tunnels are being built using 2 tunnel boring machines (TBMs) so the community and businesses can continue above ground while work happens below ground.

Digging the 4km outbound tunnel and 2.8km inbound tunnel will be a 24/7 operation. To do this, the TBMs will excavate 1.5 cubic metres of rock and soil from the tunnel, which is enough to fill the MCG.

How do TBMs work?

TBMs operate like moving underground factories, using their giant cutting heads to dig through the soil and rock. The 2 TBMs on the West Gate Tunnel Project, named Bella and Vida, will dig up to 27m under Melbourne’s west while progressively installing a watertight concrete lining behind them to create the new tunnels.

Each machine weighs around 4000 tonnes, are 90m long and span 15.6m in diameter – as tall as a five-storey building. Behind the TBMs, crews will work to build the road surface and install electrics, ventilation and safety systems.

The cutter heads on the front of the machines are powerful enough to spin 2 A380 aeroplanes, with a total of 2 revolutions per minute.

The TBMs have started tunnelling from our site on Whitehall Street in Yarraville where the inbound exit and outbound entry are located and they move south west towards the West Gate Freeway near South Kingsville where the inbound entry and outbound exits to the tunnel will be located.

Work has started on the outbound tunnel first, closely followed by the inbound tunnel. The longer outbound tunnel will take around 18 months to dig.

In February 2023, TBM Vida broke through in Yarraville, completing a 2.8km journey that started on the west side of the Maribyrnong River under Yarraville and finished at Williamstown Road near the West Gate Freeway. Relive the moment when TBM Vida broke through the head wall.

Introducing our TBMs Bella and Vida

Tunnelling tradition dictates a TBM cannot start work until it has been given a female name, a sign of good luck for the project ahead. This tradition dates back to the 1500s when miners and military engineers working with explosives, for underground excavation, prayed to Saint Barbara for protection.

Our TBMs are named after 2 notable Victorian women:

What’s it like working inside a TBM?

Specialised training is required to operate a TBM. This training includes spending time inside a special hyperbaric chamber so workers can learn about operating in pressurised conditions.

Workers will work up to 35m below ground level and will need to spend up to 2 hours depressurising before returning to the surface.

Up to 20 people will work in the TBM at any one time.

Noise and vibration

To provide peace of mind while we build the tunnels, the project will also:

  • inspect properties above the tunnel before and after construction
  • monitor ground movement and vibration levels at all times
  • meet strict targets set to manage vibration and minimise disruption.

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