COOL ENGINEERING! City Rail Link is a complex transport infrastructure project and the largest ever to be undertaken in New Zealand.
While construction of the new CRL stations has yet to start, the project has already seen some awesome engineering feats since work began in 2015, including the weight transfer of a 106-year-old heritage building and construction of underground tunnels through busy urban environments. Our construction areas in downtown Auckland and Mt Eden have also seen their fair share of cool construction equipment from big piling rigs to tunnel boring machines.
Trenching and tunnelling under the central city
intersection thanks to a one-metre deep concrete bridge deck constructed over the top, enabling tunnelling to continue underneath.
More than 600 metres of CRL tunnel box has already been constructed under Albert St between Wyndham and Customs Sts, joining the CRL tunnels built under the Commercial Bay development, Lower Queen St and Britomart Station.
Over the past three-and-a-half years, over a million hours were worked on this Albert St site, 2,500 tonnes of steel bar reinforcement tied together and over 10,000 cubic metres of concrete poured. In that time, many kilometres of stormwater, electrical, gas, sewerage and internet lines were also relocated or strengthened.
During the trenching and tunnelling works on Albert St, traffic has been able to continue using the road, safely separated from construction trucks, due to the building of 400 metres of special construction road made of concrete slabs sitting 18 metres above the trench.
The Link Alliance will build the remaining CRL tunnel sections from Albert Street to Mt Eden.
Traffic was also able to continue using the busy Customs St
An uplifting experience
Before we could start constructing CRL’s rail tunnels under Britomart Station and Lower Queen St, we spent two years carefully preparing the station’s historic Chief Post Office (CPO) building to be transferred on to 20-metre-deep temporary foundations. Safely transferring the stone building’s 4000-tonne weight was one of the most complicated engineering feats undertaken in New Zealand to date. It’s also the heaviest building ever to be moved in this country – and a Category 1-listed heritage building to boot!
Pipe-jacking power
Two mini tunnel-boring machines (TBMs) have helped pave the way for CRL tunnel and station works by ‘pipe-jacking’ new stormwater lines away from future tunnel and station construction zones. Sometimes referred to as a “mole”, a TBM excavates tunnels using a circular cross-section of blades. We used a TBM named Jeffie to divert a 420-metre section of stormwater main that was in the path of the future CRL tunnels at Mt Eden, creating a new alignment between Water and Nikau Streets. Sixteen-metre-deep shafts were constructed to provide underground access for Jeffie, who simultaneously excavated and installed the new watermain, using 215 separate concrete pipe segments. In Albert St, a TBM named Valerie (after Olympic shotputter Dame Valerie Adams) installed 490 metres of replacement stormwater main on the eastern side of Albert St, away from CRL tunnel construction. At the same time, the central city’s main sewer line, sitting 20 metres underground, was strengthened and rebuilt – all the while keeping Auckland’s traffic flowing above ground.
Painting the town red
Reaching new heights
A bright red 90-tonne piling rig named Sandrine played a major part in preparing for tunnel construction under the CPO building, helping to construct 64 diaphragm walls (or D-walls) to provide structural support. D-walls are constructed using an engineered fluid, typically a sodium bentonite mud (an absorbent clay that expands when wet), which is later replaced by permanent concrete. A specialised bentonite plant with large red silos was shipped over from France and set up on Lower Queen St for this work.
A nine-storey-high piling rig - affectionately named after 1960s TV character Gomer Pyle - was a common site at the lower end of Albert St in the early days of CRL construction. Gomer dug a total of 372 piles of up to 20 metres to provide ground support for the CRL trench stretching from Wyndham to Customs St.
Visit
CityRailLink.co.nz CityRailLink
for more information on CRL construction methods and machines.