QUEENSLAND'S GERMAN CONNECTIONS - PAST, PRESENT AND FUTURE

Brisbane being bored

Tunnelling Construction of the Airportlink and Northern Busway tunnels was carried out using a combination of three techniques:

• Roadheader tunneling – approx. 8.7km length • Cut and cover construction – approx. 2.3km • Tunnel Boring Machine (TBM) – approx. 4km Roadheader tunnelling

A total of 17 boom-type roadheader machines, the largest number on an Australian infrastructure project, excavated sections of the Airportlink and Northern Busway tunnels. Each machine: • weighs 135 tonnes and is 18.2m long • cost between $2.5 and $5 million • requires 7 workers required to operate • has a conveyor belt to transfer the excavated soil and rock to a spoil truck • has a rotating cutting head with up to 72 picks for hard rock and up to 57 picks for soft rock • has a high-pressure pick-flushing system to minimise dust and cool the cutting tool Cut-and-cover construction A technique often used to build underground structures in busy inner-city areas rather than open excavation, which would cause significant disruption to traffic. This was used in parts of Bowen Hills, Windsor-Lutwyche, Toombul, and Kedron for both the Airportlink road and Northern Busway tunnels. It involves: • Piling to support the tunnel excavation area • Excavation of soil to the tunnel rood level • Construction of the tunnel roof • Earthworks to fill the site • Excavation of the remaining soil underneath the tunnel roof concrete slab • Construction of the tunnel wall and floors TBMs • Cost $45 million each • At 12.48m diameter, the largest ever operated in Australia • Each 195m long • Each weighs 3.600 tonnes • 12 months to manufacture each one • 3 months to assemble on arrival in Brisbane • 22 people to operate each machine Workers watch as one of the TBM cutting wheels is carefully lowered from the ‘launch box’ at Kalinga on 27 April 2010, to begin its subterranean re-assembly and journey into Brisbane’s underground history. Image courtesy BrisConnections

Two identical TBMs were specially designed and manufactured by Herrenknecht in Germany for use on the Airportlink project. State of the art tunneling machines are extremely safe to excavate in softer ground (found in the Toombul area) while also cutting through rock 6-8 times harder than concrete. The TBMs were custom made for the project and were the largest to ever operate in Australia.

295