Tunnelling on – the NZ Transport Agency’s Waterview Connection in Auckland – will stop for two to three weeks on Monday (5 May) for essential maintenance work on Alice, the project’s tunnel boring machine (TBM).
Hundreds of steel fibre brushes installed on the shield (front section) of the TBM need to be replaced. The brushes help to form a waterproof seal as the concrete segments that line the tunnel are lifted into place by Alice as she journeys underground.
NZTA highway and network operations manager, Tommy Parker, says replacement of the brushes was expected sometime during Alice’s 2.4km journey from Owairaka and Waterview to build the first of the twin tunnels.
“We decided it would be prudent to replace the brushes now, before we possibly encounter more onerous groundwater conditions later in Alice’s journey.”
Parker says tunnelling is continuing until Monday and approximately 800 metres of tunnel is now constructed. About a third of the 12,000 concrete segments that form the southbound tunnel’s lining have been erected.
“The maintenance work on the steel fibre brushes will not affect other construction work in the tunnel. In fact, we can use the time to make faster progress on the concrete service culvert which is being built behind Alice.”
The culvert will carry the services needed to operate the two completed tunnels, which are due to open in early 2017.
Parker says Alice may now “break-through” at Waterview in late September, two to three weeks later than was originally planned. She and her trailing gantries will then be turned around over the following three months, ready to begin building the second tunnel from Waterview to Owairaki.
The twin tunnels, both 13.1m in diameter, are being constructed to connect Auckland’s Southwestern (SH20) and Northwestern (SH16) motorways as part of the city’s Western Ring Route. Each tunnel will carry three lanes of motorway traffic.
