Tunnelling
Construction of Airport Link and Northern Busway (Windsor to Kedron) involved a total of 15 kilometres of tunnelling, which encompassed road and busway tunnels and their connecting ramps.
Airport Link
The 6.7 km toll road features twin 5.1 kilometre tunnels connecting Brisbane city with the northern suburbs and airport precinct, with entry and exit portals at Bowen Hills, Kedron and Toombul.
Northern Busway (Windsor to Kedron)
The 3 km busway features a 1.5 kilometre busway tunnel between Truro Street in Windsor and Sadlier Street in Kedron.
> Tunnelling Operations fact sheet
Tunnelling Progress
Tunnelling operations occurred around the clock, 24 hours a day, 7 days a week at the following worksites:
- Bowen Hills
- Lutwyche
- Northern Busway
- Kedron
- Wooloowin
- Toombul
Tunnelling Techniques
Construction of the Airport Link and Northern Busway tunnels was carried out using a combination of three techniques:
Roadheader tunnelling – approx 8.7km- TBM tunnelling – approx 4km
- Cut and cover construction – approx 2.3km
Roadheader Tunnelling
A total of 17 roadheader machines, the largest number on an Australian infrastructure project, excavated sections of the Airport Link and Northern Busway tunnels.
The machines are powerful, boom-type roadheaders with unique cutting technology to excavate hard rock.
Fast Facts
- Weight – 135 tonnes each
- Length – 18.2 metres
- Cost – Between $2.5-$5 million each
- 7 workers to operate each machine
- Each machine has a conveyor belt to transfer the excavated soil and rock to a spoil truck
- The rotating cutting head features up to 72 picks for hard rock and up to 57 for soft rock
- High pressure pick flushing system to minimise dust and cool the cutting tool
TBM Tunnelling
The two largest Tunnel Boring Machines (TBMs) to operate in Australia excavated the Airport Link mainline tunnels.
Two identical TBMs were specially designed and manufactured by Herrenknecht in Germany for use on the Airport Link project. These state-of the-art tunnelling machines are extremely safe to excavate in softer ground (found in the Toombul area) while also capable of cutting through rock 6-8 times harder than concrete.
- TBM tunnelling fact sheet
- TBM spoil operation fact sheet
- TBM mechanical and electrical fit-out fact sheet
- Frequently asked questions
- TBM alignment map
Fast Facts
- Model—Earth Pressure Balance
- Cutterhead diameter—12.48 metres
- Weight—3,600 tonnes
- Length—195 metres long, slightly longer than Suncorp Stadium playing field
- Cost—$45 Million each
- Cutterhead contains up to 80 x 17 inch cutters made of hardened steel
- Approx. 22 workers to operate a TBM
- Travels up to 55m below the surface
- Equipped to install full-circle concrete tunnel lining during excavation
Cut-and-cover construction
Cut-and-cover is a construction technique often used to build underground structures in busy inner-city areas rather than open excavation, which would cause significant disruption to traffic.
Cut-and-cover tunnel construction was used in parts of Bowen Hills, Windsor-Lutwyche, Kedron and Toombul for both the Airport Link road and Northern Busway tunnels. It involves the following steps:
- Piling to support the tunnel excavation area
- Excavation of soil to the tunnel roof level
- Construction of the tunnel roof
- Earthworks to fill the site
- Excavation of remaining soil underneath the tunnel roof concrete slab
- Construction of the tunnel floor and walls
