Alice the boring machine breaks through the end of the first tunnel. Photo / NZTA
We know that Alice, the boring machine at Waterview, has reached the northern portal of the tunnel, and now has to be turned around for the return journey. How is this done? Anne Martin, Henderson.
Devilish clever, these engineering chaps. They use whatever is at hand.
In this case, it's
sheep. About 200 litres of lanolin - the wax or grease extracted from sheep's wool - will be used to help slide the project's giant tunnel boring machine into position so that it can start excavating the second of the twin motorway tunnels.
"Shifting Alice is probably one of the most technically challenging tasks of the whole Waterview project," says the Transport Agency's highway manager, Brett Gliddon. "It's not unusual internationally to turn a tunnel-boring machine, but what makes this operation extraordinary is the sheer size of Alice - she is the 10th largest of her kind in the world - and the very tight space the project team has to manoeuvre and turn her. "That's where the lanolin from our sheep plays its part. It has the right qualities to be added to the cocktail of grease necessary to help slide Alice around in such a constrained area."
Alice is almost 88m long and too big to be turned in one piece. She is now being separated and brought out one big piece at a time. The first section - the 2400-tonne shield that includes the cutting head - is waiting to be turned and moved across 20m. The shield will be re-launched southwards in late November to bore the first 300m of the second tunnel to allow the other sections to be reconnected. Tunnelling will fully resume next March and the final breakthrough is expected by September.
