With the completion of all tunnelling excavations at the Waterview Connection project, tunnel boring machine (TBM) Alice is now being dismantled into sections and cleaned up before heading back to Germany.
The tunnel team recently completed the excavation of the last of the 16 cross passages that connect the two motorway tunnels.
The cross passages are about 11m long and will be used to evacuate people if there is an emergency underground, and to house equipment to operate the tunnels.
Construction began on 11 November 2013 when Alice started excavating the first tunnel. It ended just over two years later with the excavation of Cross Passage 2.
Although excavation is complete there are still many months of work ahead – constructing the road surface, installing concrete linings, lights, drains, the deluge safety system and signage as well as painting the ceilings and walls – before the tunnel opening in early 2017.
Meanwhile, Alice continues to shrink by the day.
Crews have been busy dismantling the TBM since she broke through from the Owairaka (southern) end of the tunnels in October.
In what is a technically difficult operation, the huge machine is being taken apart in large sections, lifted out of the trench and cleaned before shipping back to Herrenknecht, the German company that designed and built the TBM.
“Dismantling Alice has taken a lot of work and planning,” says NZTA Auckland Highways Manager Brett Gliddon.
“It’s a very tight fit to get some of these pieces out, and sometimes there’s been as little as 200mm to spare.”
The giant 322-tonne cutter head that carved through underground spoil to drill the tunnels was recently lifted out of the trench.
Six hydraulic jacks were used to push the cutter head from the 184 studs that held it in place on the main drive of the TBM.
A 600 tonne and 300-tonne crane were then used to lift it out of the trench and onto a concrete slab where it was cleaned and separated into five smaller sections for transportation.
“Lots of people have asked us whether we can use Alice for other tunnelling projects in New Zealand, but each TBM is built specifically for one job,” says Gliddon.
It’s designed to take into account the size of the tunnel and the type of material it’s boring through, which are individual for each project,” says Gliddon.
The dismantling process for Alice is expected to be completed by the end of summer.
