Giant tunnel machine testing begins
The big dig is continuing.
It has been a year since physical work began on New Zealand’s largest infrastructure project and progress is slowly but surely edging towards the moment when the much-anticipated tunnelling work can begin.
An enormous tunnel boring machine that will spend two years creating the Waterview Connection has been built in China and is being tested next week.
Once testing is complete, the monstrous machine will be broken down into 90 pieces, each weighing up to a couple of hundred tonnes, and shipped to Auckland in July to be reassembled on site.
Those working on the job describe the boring machine as a ‘‘living, breathing building’’.
Actual tunnelling is set to begin in October and will see the giant machine – three storeys high and 100m long – spend a year trundling north before exiting the tunnel, turning around and heading back south for the other lanes.
It is the tenth largest tunnel boring machine ever used in the world, will be guided by satellite and will travel at a speed of 0.005kmh, churning through 4 metres of material a day.
As it travels it will spit the spoil out behind it by conveyor belt, which will be stockpiled and removed by trucks running every five minutes, 24 hours a day.
As it progresses it will also install curved concrete walls which are being precast now at a purpose built factory in East Tamaki.
The Well-Connected Alliance of New Zealand and international contractors are doing the work.
New Zealand Transport Agency Auckland and Northland State Highways manager Tommy Parker says it will be a mammoth task but one the alliance is confident of seeing through without any dramas.
‘‘The critical target now is getting ready to bore, which is the coordination of a number of work streams that we need to come together,’’ he says.
‘‘Primarily it’s the southern access trench which the machine will be lowered into.’’
Getting the trench ready has involved blasting through 15m of hard basalt rock to reach the softer limestone sediment rock below.
Diggers need to go down another 15m before the 40m wide trench will be ready to accommodate the vast machine.
Mr Parker says the basalt has proved to be harder than anticipated and has taken a huge effort to break through.
It has made the early part of the project more difficult but bodes well for the next phase.
‘‘We’re not expecting any tunnel vibration. It’s an absolute bedrock, hard as.’’
As with any major project, there are potential pitfalls ahead.
‘‘The biggest risk is hitting unforseen rock forms, but we’ve done all the testing we can. We have a very detailed model but there’s always the risk of hitting something.’’
A big focus of the job is to leave the area surrounding the job site in an improved state once the work is complete.
Major efforts are being put into improving Oakley Creek, and walk and cycle ways will better link the Waterview suburb with Pt Chevalier and the city.
Mr Parker says improving the skill set of the industry is also a goal and there will be a concerted effort to train New Zealanders in the art of tunnelling.
‘‘We have a scheme where trained drivers and technicians are brought in and they will train up local staff.
‘‘We want tunnelling capability in New Zealand.’’
Big dig: NZTA Auckland and Northern State Highways manager Tommy Parker and Fletcher surface works construction manager Malcolm McDonald in front of what will be the southern access point for the Waterview Connection tunnel. Workers have to dig down another 15m before tunnelling can begin.
Deep down: The enormous three-storey high, 100m long tunnel boring machine will begin its journey here in October.