Airport Link TBMs buried

The TBMs that excavated the Brisbane Airport Link were last week entombed with concrete in reception pits beneath the Link tunnels. Excavation finished on the project with the final breakthrough on 6 July.

The two burial pits were 14.5m wide and 16.5m deep and were excavated by drill and blast and rock hammer by contracting JV Thiess John Holland. The TBMs were fully encased in 2,500m3 of concrete over 24 hours. The process finished on 22 July.

A spokesman yesterday told T&T, “The machines were lowered using a purpose designed and built steel bridge structure, connected to six 330-tonne specialist strand jacks. The lowering took around 6 hours from the initial pickup of the beams until completely lowered in the shaft.

“The final lining in the burial shaft area will be formed insitu concrete on the walls and permanent shotcrete in the roof. By encasing the machines in concrete, no ground water will be able to come into contact with the machine shields and cutterheads, eliminating any possible contamination.”

The spokesman added, “The last 180m of each machine, containing the backup gantries and conveyor belts, are currently being removed for recycling and reuse where possible. With tunnelling now complete across the project, demobilisation is underway of the tunnel support facilities located in Kalinga Park including the 2km long overland conveyor, grout plant and chilled water.

“With less than 12 months until project completion, the project is in its final phase of construction and fit out, ready for a mid 2012 opening.”

The machines, Rocksy and Sandy, were 12.48m-diameter Herrenknecht EPBMs equipped with 80 cutters of 17-inch diameter.