Kia ora neighbours,
We hope that you and your loved ones are safe and well following the move to COVID-19 alert Level 4 restrictions.
The Karangahape Station site, along with all City Rail Link sites, have ceased construction for a minimum of seven days (from 17 August 11:59pm).
In this update we will provide you with the latest - pre lockdown - construction news from Beresford Square, Mercury Lane and the mined tunnels; in addition an update on the progress of the Tunnel Boring Machine (TBM).
Excavation has been continuing at both Mercury Lane and Beresford Square.
In Mercury Lane we hit a major milestone with the tunnel breakthrough from the main station box to the pilot tunnel. Check out the video of the break through moment: https://www.youtube.com/watch?v=PuwFIHNmaK8
The southbound tunnel (MC30) profile is complete and work is now directed to the northbound tunnel (MC20). It is expected to be completed early next year.
Key milestones for Beresford Square were the last two concrete pours for B2 and the commencement of excavation from B2 to B3.
A surveyor walking through the tunnels and station boxes uses a laser scanner to take the images seen below. They scan the interior of the tunnel and station box and capture their environments in 3D and in real time. This is called a Building Information Model (BIM).
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Progress in Mercury Lane
As mentioned above, a key milestone was reached in Mercury Lane last week with the breakthrough from the station box to the mined pilot tunnel below.
The breakthrough occurred 18 metres below the station entrance under construction at Mercury Lane – the building is now connected directly to the mined tunnel excavations underway for the Karangahape platforms.
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The BIM image above shows where the breakthrough point was located. Also shown are the completed first three levels of the station, entrance/L0, B1 and B2.
The Mercury Lane team is excavating to the deepest floor B7 and the methodology will change to 'bottom up' construction, that consists of excavating / rock bolting / shotcreting.
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The images above and below show the vibro ripper breaking through from the station box to the pilot tunnel.
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 below that had been used to excavate the platform tunnels.
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Excavation under the street-level slab began in early March and within five months, with two floors completed and 16,000m3 of spoil removed the station structure is now connected to the mined tunnels beneath.
The pilot tunnel was constructed underneath the footprint of the station box in advance of the station construction, in order to provide access to multiple work fronts for the mining team.
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With access now available from both the station box and the mined tunnel shaft, resources can be shared between the teams to excavate the remaining 16,500m3 of rock required for the station box.
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We have completed L0 / B1 / B2 now and are excavating / rockbolting / shotcreting down to B7.
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Mined Tunnels
Excavation work is now complete on the southbound tunnel closest to Mercury Lane and work has now begun on the northbound tunnel closer to East Street.
The completed tunnel is seen as the green section in the image below. The blinding (temporary concrete floor) is on the ground and 100% ready for the arrival of the TBM rails.
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The white section of the BIM image above depicts MC20 - the northbound mined platform tunnel that is now being excavated with completion expected this September.
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Above is Adit 5 with excavation complete to beneath Beresford Square.
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With the completion of the tunnels the floor is lined with a sacrificial layer of concrete called blinding, making it ready for the installation of temporary rails for the arrival of the TBM. Wet sandstone from the excavation can form a muddy looking film on top of the blinding layer.
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Tunnel Boring Machine
The 130-metre Tunnel Boring Machine (TBM) named after Dame Whina Cooper has so far travelled over 320 metres towards Mercury Lane.
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The machine excavates the bored tunnels by cutting rock with a massive cutter head and transporting the spoil to the surface, through the tunnel, on a conveyor belt. Precast segments are then installed as the permanent tunnel walls.
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Check on the photos for an explanation of each and you can follow the TBM progress at https://www.digcrl.co.nz/
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When the TBM arrives at Karangahape Station the TBM will push itself through the mined tunnel on temporary rails.
The TBM will first pass through MC30 - the southbound mined tunnel - that has been excavated using a combination of road headers and excavators.
This methodology was selected to enable both parts of the project – the station entrance box and tunnels - to be constructed concurrently, creating efficiencies for the project program. |
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Learn more about the TBM at the Te Manawa visitor centre at 1 New North Road, Eden Terrace to view a model of the TBM and learn more about his amazing piece of machinery.
The centre is open on Mondays 11am to 1pm, and 4pm to 6pm; and on the first Saturday of every month, 11.30am - 1pm.
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Progress in Beresford Square
Key milestones for the Beresford Square entrance were the first two concrete pours for the B2 level and the commencement of excavation from B2 to B3.
In the BIM image below you can see the entire surface area of the station entrance floor, the completed southbound tunnel MC30 shown in green, and the white section is the northbound tunnel MC20 that is now being excavated.
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Steel fixing for B2 is almost complete and the last of the concrete pour is scheduled for later this month. Now excavation has begun for B3.
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Trucks line up in Beresford Square for the last of the concrete pours.
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Concrete trucks feed the concrete pump at Beresford Square.
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The white arm is the concrete pump at Beresford Square.
Excavation has now begun from B2 to B3.
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It is now too deep for the long reach excavator so all the spoil is coming out via a crane with a bucket that is lowered into and out of the cavern.
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Trucks drive under the gantry frame, the bucket is maneuvered above and the spoil is dropped into the truck.
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Ongoing excavation at Beresford Square B3.
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