Gi­ant tun­nel ma­chine test­ing be­gins

Auckland City Harbour News - - NEWS - By JOE DAW­SON

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.

Pho­tos: JOE DAW­SON

Deep down: The enor­mous three-storey high, 100m long tun­nel bor­ing ma­chine will be­gin its jour­ney here in Oc­to­ber.

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