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VSL strand jacks and pumps were used to lower the TBM shields for burial.

The Airport Link is a tunnelled motorway-grade road that is under construction in the northern suburbs of Brisbane. It involves 15km of tunnelling, including 5.7km of twin tunnels for the road, bus-way tunnels and connecting ramps, as well as 25 bridges. Together this results in more than 7km of new road.

In order to achieve the ambitious deadlines set for the project, two tunnel boring machines (TBMs) were used for the construction of the main tunnels under the city of Brisbane.

The primary contractor responsible for the prestigious AU$4.8 billion scheme is TJH, a joint venture of two major Australian companies, Thiess and John Holland. VSL carried out a key operation to relocate the TBMs once tunnelling was complete.

Not only are TBMs one of the most cost and time efficient ways to build tunnels, but they also offer a high level of safety for one of the most dangerous activities in construction.

Modern TBMs typically consist of: a rotating cutting wheel called a cutter head TBM shield; a main bearing; a thrust system; and trailing support mechanisms.

TBMs are generally only designed to move forward, and can only be recovered at the end of tunnelling if there is sufficient open space available.

The configuration of the project and the size of the TBMs meant that, on completion of the tunnelling, the TBM shields had to be lowered into a specially dug pit and buried in mass concrete underneath the future roadway.

VSL Australia was appointed by TJH at the end of 2010 to design the temporary lowering structure and supply and operate the TBM lowering equipment.

In turn, VSL Australia appointed VSL’s Technical Centre Asia/Australia (TCAA) to design the temporary works required for the lowering. VSL proposed its own unique solution using its strand jacking equipment to perform the challenging lowering operation, which was completed in record time. It was able to do this as a result of experience gained on a similar project at CERN in Switzerland.

Scope of works performed

  • Design and engineering of the lifting structure
  • Supervision of the lifting structure installation
  • Supply of strand jacks and pumps
  • Lowering of the TBM shields


The first step of the project was the design and installation of a temporary steel structure to support the TBM over the burial pit and lower it into its final position.

The steel structures were installed under VSL supervision. An independent check was completed to certify the structure before proceeding any further with the operation.

The second step was the installation of the VSL strand jack and pump that held the lowering structure and allowed the TBM shield to slide in ready for the lowering operation.

It took six VSL hydraulic jacks to lower each TBM shield, which weighed approximately 1,300t and had a diameter of 12.45m. The jacks were divided into three groups of two and the lowering operation was a similar arrangement to a three-point lift. The operation used SMU330/550 jacks combined with EHPS 32 hydraulic pumps.

A crew of five VSL staff was required to perform the lowering operation. The team consisted of a lifting technician from Switzerland, a site engineer and three supervisors/leading hands.

Lowering was carried out at a rate of approximately 300mm every five minutes and the TBM shield was lowered 13.5m into its final position in less than five hours, without any incidents.

Using an inclinometer and pressure monitoring devices on the jacks, the orientation of the lowering structure was kept level to avoid any lateral movement of the TBM shield.

Once the final position was reached, mass concrete was poured below, around and on top of the shield to encapsulate it and mitigate any risk of pollution.

The ambitious project has proved a huge success for VSL, which was able to showcase its technical capability on such a demanding project. The client TJH expressed satisfaction on several occasions.

VSL’s Heavy Lifting equipment is reliable and performs perfectly, making VSL the partner of choice for such projects.