Alice makes progress underground
The boring machine responsible for Auckland’s Waterview tunnels has burrowed underground on the first part of its two-year return trip from Owairaka to Waterview.
Known as Alice, the 2200-tonne machine has so far chewed through 12 metres of soil. The first of the 2414 reinforced concrete rings that will line the two tunnels have been installed.
NZ Transport Agency highways manager for Auckland Tommy Parker says it’s a balancing act.
‘‘It’s been important to temper the machine’s enormous power to prevent her from damaging temporary support structures as she entered the ground.’’
The machine stops work every two metres to lift the concrete tunnel lining rings into position. Each completed ring is then grouted into place.
Mr Parker says Alice is boring at 40mm per minute compared with her top speed of 80mm but will work at a faster pace when more lining rings are installed.
A conveyor system will remove about 800,000 cubic metres of excavated material from the tunnels and take it to a building almost one kilometre from the tunnel portal. From there it will be taken to a disused quarry which is being rehabilitated for industrial development.
Alice operates 24 hours a day with crews of about 20 people and at least as many others working in support of the tunnelling operations. Tunnelling will be put on hold for several weeks in the new year to prepare for the construction of a ventilation shaft building at the southern portal. The tunnels are due to open in early 2017.