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New record for McConnell Dowell’s micro tunnel boring machine

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World Trenchless,

McConnell Dowell’s micro tunnel boring machine (mTBM) beat its previous project record by 80 m on 20 November 2020.

The AVN2500 mTBM set a new pipe-jacking record for the longest single drive in the Southern Hemisphere by a tunnel boring machine greater than 2.6 m in diameter. The project set a 1216 m record on completing the second drive for the pipeline earlier in 2020.

The new record is an achievement for the team delivering the 3.5 km water mains upgrade for Watercare. The final 1296 m drive consisted mostly of basalt rock and tough clay ground conditions, but despite the geological challenges, the crew completed the final drive in less than three months.

With 2.9 km of tunnelling now completed, Amiria, one of McConnell Dowell New Zealand’s three mTBMs, will be refurbished by the company’s in-house mechanical and maintenance team. The next step for the project team is the installation of the 1575 mm diameter concrete-lined steel watermain pipes inside the tunnel, which is planned for early 2021.

McConnell Dowell’s proposed trenchless methodology won the contract to design and construct the final section of the Hunua 4 pipeline in 2018. Rather than digging trenches through some of Auckland, New Zealand’s busiest roads, the tunnelling approach meant traffic continued to flow between Epsom, New Zealand, and the Auckland, as the pipeline was built underneath.

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