The four-storey-high cutterhead has been lowered 27m into the ground in Footscray bringing the project another step closer to start tunnelling.

The positioning of the 450t cutterhead was undertaken using a 500t gantry crane to first lift it from horizontal to vertical and then moving it over the launch site before being lowered into place.

The cutterhead is the main boring tool that sits on the front of TBM Bella, made up of five separate pieces welded together and featuring 96 mounted cutters.

The cutterhead breaks through the rock and dirt in front of it like a huge drill bit. As it rotates, the cutting discs break down the rock and dirt to dig the tunnel.

The cutterhead will rotate up to almost two times per minute during normal tunnelling operation and up to 3.5 times per minute when cutting through dense rock sections.

With the TBM being assembled from back to front, Bella's cutterhead, which is located at the front of the machine, is one of her last components to make its way underground.

The assembly of the second TBM Vida will soon commence for tunnelling to start later this year.

Bella and the other TBM Vida will build two tunnels ready to opening in 2022 to provide a vital alternative to the West Gate Bridge, quicker and safer journeys and remove over 9000 trucks from residential streets in the inner west.

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