Mega TBM arrives in Melbourne 07 Mar 2019

The first of two 15.6m diameter mega TBMs has arrived in Melbourne, Australia to prepare for its 4km long drive on the city’s West Gate twin tube highway tunnel project.

15.6m cutterhead preparing for TBM assembly

After arriving by ship from the Herrenknecht factory in China, the components of the machine were trucked to the north portal of the drive where it is now in assembly for launch on the outbound tunnel by mid-2019. The second twin machine, also manufactured by Herrenknecht and to be shipped from its factory in China, is programmed to arrive in mid-2019 and be assembled and launched before the end of the year to complete the shorter 2.8km inbound tunnel of the project. Both machines will begin their journeys at their northern portals and progress south-west towards the southern portal junctions to the existing West Gate Freeway (Fig 1).

The two mega machines are procured by the 50/50 design-build CPB/John Holland JV which is engaged by the toll highway concessionaire Transurban under its PPP (private-public-partnership) agreement with the State Government of Victoria. Transurban is commissioned to build and operate the new highway which will provide a bypass, particularly for heavy truck traffic away from the city centre of Melbourne and create a new access across the Yarra River to relieve serious congestion and vulnerability of the West Gate bridge as only existing link across the river and links with the city’s City Link toll highway tunnels on the east side, also operated by Transurban.

Fig 1. New highway link creates tubes of 2.8km and 4km long

The massive 15.6m diameter cutterheads are dressed with 96 x 19in cutters - six sets of twin cutters and 84 single cutters - and a triple ring hydraulically operated over-cutter. In addition there are 152 scraper tools and 16 outer scrapers on each cutterhead. The machines are designed as EPBMs to work through sedimentary deposits on their alignments under the Maribyrnong River (a tributary of the Yarra River) and with a section of hard rock to be negotiated on the longer 4km long drive outbound drive.

The giant machines have about 12MW of total installed electrical components and a new substation has been built on the northern portal launch site to supply about 10 MW of electricity from twin mains feed supplies to power each on a 24 hrs/day, 7 days/week schedule. With a variable speed of 0 to 1.9 rev/min in normal operation, and up to 3.5 rev/min for the outbound machine through its section of rock, maximum nominal torque on the cutterheads is 68,000kNm.

As the machines advance, 500mm x 2.4m long rings of 10 segments line the three-lane highway tunnels to their 14.1m internal diameter. The segmental ring is a universal taper ring with a taper of 40mm (+/-20mm) so that the key can be built in all 20 possible locations.

With major tunnelling works set to start this year, legislation has also been introduced into the State Parliament to provide the framework for the management of the new highway when it opens in 2022. The West Gate Tunnel Bill and amendments to the CityLink Concession Deed will provide a fairer tolling regime for traffic users and remove historical clauses that would see Transurban compensated for State projects that divert traffic off its existing toll network.

Estimated in last report at AUD$6.7 billion, the project has included provision of better city connections, additional noise walls, and extending air quality monitoring.

In speaking of the new highway investment State Premier Andrews said: “All it takes is one crash to turn the West Gate bridge into a car park. We desperately need this second river crossing and we are not wasting a minute delivering it. The West Gate Tunnel will cut travel times dramatically and get trucks off the local streets of Melbourne.”