The laying of tracks on one of Melbourne’s biggest ever rail tunnel projects is set to begin.

The Victorian Government has announced that work is now underway to prepare for laying of track through tunnels on the $11 billion Metro Tunnel Project.

Set to link the Sunbury line in Melbourne’s north-west with Cranbourne and Pakenham lines in the south-east via twin nine kilometre tunnels and five new stations when it opens in 2025, the project will untangle the City Loop and enable more trains to run more often in Melbourne, save 40 and 30 minutes on return journeys for Sunbury and Cranbourne/Pakenham commuters respectively and connect to the future Melbourne Airport Rail line via Sunshine in Melbourne’s west.

Work on the rail tunnel and station fitouts has been ongoing since four tunnel boring machines completed excavating the two tunnels last May.

Inside the tunnels crews are fixing brackets and cable trays to the tunnel walls (see above image) to hold electrical and communication cabling in place, as well as installing fire safety pipework and signaling equipment.

A particular feature of the tunnel preparation works are specially designed gantries with bespoke lifting arms which travel the length of the tunnel on wheels.

These enable workers to carefully maneuver the equipment into place as they go and enhance safety by reducing the need for manual handling.

Across the 18 kilometre of tunnel length, workers will install almost 50,000 brackets, 15km of elevated steel walkway for emergency and maintenance access, almost 500km of electrical and fibre cables, 16km of pipework to carry fire retardant, and more than 3,000 lights.

Installing the track itself will take up to a year.

First, crews will lay 4,000 high-performance precast concrete panels through the twin tunnels.

The panels form up to 300 different shapes to account for varying curvature and election of the tunnels a as they wind from Kensington to South Yarra up to 30m underground.

Similar to track used in other world class metro systems, these panels require less maintenance compared with conventional surface railways tracks which use sleepers laid on ballast.

Beginning in mid-2022 crews will install 165 metre lengths of steel rail. The rail will be progressively clipping to the concrete panels and welding together to form a continuous rail line along the length of the tunnels.

After this, power and new high-tech signaling will be installed into the tunnels and stations along with more than two kilometres of platform screen doors.

Finally, testing will begin in the tunnels with a fleet of larger and more modern trains.

In terms of the station fitouts, meanwhile, platforms are taking shape up to 30 meters underground along with ceilings, stairs, walls and mechanical and electrical systems.

Crews are currently installing escalators and lifts as well as fitting out back of house equipment rooms.

Victorian Premier Daniel Andrews welcomed commencement of the track laying.

“The Metro Tunnel will slash travel times and create space for hundreds of thousands more passengers across the network, making travel faster, more reliable and more comfortable,” Andrews said.

“Whether it’s building schools, hospitals, upgrading roads or building the Metro Tunnel – we’re delivering our promises and getting things done.”