By Lynda Myer
Connection of two sections of New Zealand’s deepest railway station have been done due to underground advancement at City Rail Link’s Karangahape station in Auckland.
While the location of this breakthrough is18m beneath the station entrance under construction at Mercury Lane, currently the building is linked straightly to the mined tunnel excavations that are underway for Karangahape’s platforms.
The Link Alliance’s project manager for the Karangahape station Jonathan Hill said: “It’s quite a milestone for us – one that shows we’re overcoming challenging ground conditions to ensure we are ready for the arrival of CRL’s tunnel boring machines from Mt Eden next month.”
“Within five months, we’ve laid the concrete slabs for two of the station’s floors, removed 16,000m3 of spoil, and joined up with the mined tunnels beneath,” added Hill.
The determined date for commencing the construction of the station building below street level is in early March.
A combination of Vibro-ripper and hammer working inside the station entrance excavation chiseled its way through layers of rock to open the hole in the roof of a pilot tunnel. That pilot tunnel had been used to excavate the platform tunnels.
Increasing the flexibility for sharing resources among teams to dig the remaining 16,500m3 of rock for the station, is due to the current access from both the underground station and the mined tunnels.
The risk of machinery collapse into the tunnel from above, or debris falling if the breakthrough had been tackled from below, are the potential safety challenges existing for Link Alliance workers. However, this was solved before the breakthrough by backfilling the pilot tunnel with spoil from the mined tunnel.
The Karangahape station’s underground construction, which will be 32m beneath the ground, commenced in July 2020. While the digging process of the southbound platform tunnel closest to Mercury Lane has ended, the work is underway on the adjoining northbound one. The platforms are 203m long to accommodate nine-car trains instead of the current six used on the Auckland network.
In order to improve access into central Auckland and to better link the city’s entire rail network, Karangahape is one of two underground stations being constructed for the City Rail Link project. The estimated date of opening the CRL’s tunnels with 3.45km length is in late 2024 and they are due to convert Auckland’s rail network and the way people travel around the city.
