Final tunnelling breakthrough for City Rail Link (CRL) completed in Auckland

Tunnelling

Auckland, City Rail Link, CRL, tunnelling,

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Auckland Mayor Phil Goff welcomed the milestone for Auckland’s transport network:

“The final tunnel breakthrough is the culmination of 13 months of hard work by the tunnelling teams. When complete, City Rail Link will make it faster and easier to get into and around central Auckland, doubling heavy rail capacity and ultimately carrying up to 54,000 passengers per hour in peak times. “

“It will stimulate investment, business opportunities and housing growth. It will be a critical part of the world-class public transport network that Auckland needs to succeed as New Zealand’s international city,” Mayor Goff says.

City Rail Link Chief Executive Dr Sean Sweeney said the significant achievement of boring twin 1.6km tunnels up to 42m below New Zealand’s largest and busiest city was completed under the most challenging construction conditions.

“Building an underground rail network has never been attempted in New Zealand before,” says Chief Executive Dr Sweeney. “To have achieved what this team of 2,000 people have in the face of a global pandemic, multiple lockdowns, restricted Covid-working conditions and multiple other challenges is nothing short of extraordinary.

“There is so much more to do on the CRL project, but the final breakthrough is an appropriate moment to pause and reflect on the extraordinary job our people have done in building these twin underground tunnels,” says Chief Executive Dr Sweeney.

“These tunnels are the cornerstone of the country’s first rapid transit rail network and will enable a transformational change in our biggest city.”

Key achievements during the tunnel boring phase include:

  • Completion of the tunnel-boring phase of the City Rail Link project, comprising two 1.6km tunnels

  • The TBM travelled more than 3.2 km, placed 2,118 segment rings and removed 260,000 tonnes of spoil during the boring of the twin tunnels – each 1.6kms long from Maungawhau/Mount Eden Station to Te Waihorotiu Station (Aotea)

  • More than 64,200 cu m of concrete was used to build the City Rail Link tunnels – the equivalent of 25 Olympic-sized swimming pools.

The Dame Whina Cooper tunnel boring machine weighs 910 tonnes, is 130m long and has a diameter of 7.15m

Francois Dudouit, project director for Link Alliance, the group of companies building the main contract of tunnels and stations for CRL, says the swifter finishing of the second tunnel reflected operational improvements and efficiency gains.

“I’m delighted at the performance of our team of 2,000 people who have brought their very best to this important project,” says Francois Dudouit.

“Everyone understands we are building the future of public transport in Tāmaki Makaurau, and it will leave a lasting legacy for all its people”. Whānau of Dame Whina Cooper, including daughter Hinerangi, was also present at the event:

“What a journey this has been. I think back to our beginning at Mt Eden and am so grateful we are here, together at the end,” says Hinerangi Cooper-Puru.

“Two wāhine toa have been with us throughout the TBM’s journey – my Mum and Saint Barbara (the patron saint of tunnellers). They have both endeavoured to protect our people and guided us through the tunnels’ completion.”

Now the tunnel boring is complete, Dame Whina Cooper will be dismantled and lifted above the ground. It will then be transported to the port for shipping back to its manufacturer, Herrenknecht. Parts of it will be repurposed.

About the breakthrough

  • This is the TBM’s final of four official breakthroughs for the City Rail Link project and will occur 15m underground at Te Waihorotiu Station (Aotea)
    • Boring of the second tunnel began in April 2022
    • The first tunnel took seven months, starting in May 2021 and finishing in December 2021
  • The TBM has now bored two near-identical 1.6km tunnels up to 42m below Auckland’s city centre
  • The TBM-bored tunnels will connect to the cut-and-cover tunnels previously constructed below Albert and Lower Queen Streets. The total tunnels between Waitematā Station (Britomart) and Maungawhau/Mount Eden will be 3.45km each.
  • To mark this significant achievement, members of Dame Whina Cooper’s whānau will join representatives from our Mana Whenua Forum, City Rail Link workers, the Minister of the Crown and the Mayor of Auckland to witness the occasion.

About the TBM 

  • The Dame Whina Cooper TBM is an Earth Pressure Balance machine which means it balances the pressure of the earth it excavates, which stabilises the tunnel face and reduces any possibility of settlement occurring
    • This means people above ground will feel little to no impact as it moves deep below ground
  • The TBM was custom-built for central Auckland soil conditions by the German company, Herrenknecht
  • The TBM worked 24/7, operated by an underground crew of 12 alongside another dozen workers above ground
  • At peak operation, the TBM  travelled 32m a day
  • The TBM operated at depths of up to 42m underground and averaged a speed of about 15m per day
    • This makes it faster than the average garden snail but slower than the average starfish
  • Traditional GPS tracking does not work underground, so to ensure the TBM’s accurate arrival, survey instruments called Total Stations were used to determine the machine’s exact location
  • Total Stations measure angles and distances very accurately, within 0.0001 of a degree for angles and distances to 1mm. This meant the TBM arrived in the exact right position
  • Following the breakthrough, the Link Alliance team will dismantle the TBM into separate pieces underground and lift each element by a crane above ground
  • The TBM will then be transported to Ports of Auckland and shipped back to its manufacturers overseas for repurposing

The TBM’s name 

  • In 2020, City Rail Link asked the public to name the TBM after a ground-breaking Kiwi wahine (woman) in a national competition
  • Kiwis chose Dame Whina Cooper in honour of the Māori rights champion who led the famous hīkoi to Parliament in 1975

The station 

  • Te Waihorotiu (Aotea) will become New Zealand’s busiest railway station once the CRL opens (a title presently held by Waitematā Station (Britomart)
  • Link Alliance began construction of Te Waihorotiu Station (Aotea) in November 2019
  • In under three years, the team has cleared utilities, built the skeleton of the station superstructure (above ground), and excavated most of the station substructure (below ground)
  • Excavation of the platform concourse continues underground, and teams are working on the two Victoria Street entrances
  • Te Waihorotiu Station (Aotea) will connect via tunnels to Waitematā Station (Britomart) to the north and Karanga-a-Hape Station (Karangahape) to the south, then link up to Maungawhau/Mount Eden Station and the wider rail network.
  • By the end of 2022, the focus for Te Waihorotiu Station (Aotea) will shift from heavy civils to station and tunnel fitout work, followed by urban realm work for the station streetscapes and surrounds.
  • The tunnel boring machine’s shield (the front 30 metres of the machine) will now push itself forward into Te Waihorotiu Station (Aotea) building, where it will be dismantled and lifted above the ground.
  • Te Waihorotiu Station (Aotea) is 15m deep and 300m long, with entrances at both Wellesley and Victoria Streets. It is located in the heart of Auckland’s mid-town precinct, undergoing a significant revitalisation programme.
  • The station will also feature 21-story retail, commercial, and residential tower above the station, provisionally called Aotea Central.

Source: City Rail Link media releases

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