Linking Brisbane to the airport

Australia’s largest infrastructure project Airport Link will connect Brisbane’s airport and northern suburbs to the north-south bypass tunnel and inner city bypass. Holcim Australia’s Southeast Queensland concrete team is one of the main suppliers for this impressive project.

The Airport Link, some 6.7 kilometers long (mainly underground) with costs of AUD 5.6 billion (USD 5.1 billion), is being built to an extremely tight timetable. Therefore, scheduling deliveries of supplies and undertaking construction according to the precise requirements of the project managers are critical.

2,800 cubic meters in one night
Earlier this year the Southeast Queensland (SEQ) concrete team was awarded the task of providing and placing more than 2,800 cubic meters of concrete in a marathon engineering effort over just one night. The contract called for a single pour, to create the roof for a section of the tunnel. “On the night selected, a team of 50 concreters, engineers, and laborers spent nine hours pouring the concrete at the site,” says Pauline Elliott, Key Account Manager for SEQ. “We used 48 trucks to deliver 380 loads of concrete, which were scheduled to arrive every two minutes. Four concrete pumps were needed to ensure that concrete could be poured at a rate of 300
cubic meters an hour, throughout the night.” The project is using three different methods for tunnel construction. This particular pour was the first part of the cut-and cover method. In this interesting construction technique, the pour creates the roof of the tunnel that is yet to be built. The tunnel roof is built first and then the ground below is excavated to create the tunnel itself. 

 


“This is a much faster technique and, on a project of this size, eliminates the need to set up huge
areas of formwork to support the roof. It also allows construction work to continue both above and
below the tunnel roof, speeding project completion,” says Elliott.

Continuing supply 
The SEQ concrete team continues to pump up the volume on the project, recently taking the
amount of concrete supplied to an astounding 425,000 cubic meters. “We’ve now been supplying this project since November 2008 and it’s been an outstanding effort from the whole team,” says
Mark Taylor, Sales and Marketing Manager for SEQ concrete. The team recently commenced supply of another huge section: 115,000 cubic meters of arch-lining concrete and 40,000 cubic meters of concrete pavement. For this section, the tunnel method called for road headers to excavate the tunnels.

“The arch-lining concrete is used inside the excavated tunnels and cast up against a waterproof membrane that sits against the shotcrete, which we have already supplied,” says Taylor. “It requires a high early strength and some smarts from our technical team to achieve the performance criteria. As a bonus it also looks like we can reduce the stripping time on the program for the arch lining. Concrete pavements become the structural roadway on which an asphalt overlay will be applied. Both the pavement and the arch-lining concrete are critical elements on the project and we won the supply due to our performance in service and quality.”

New concrete mix designs
To date the project has demanded many new mixes with plenty of challenges for the technical and production team, including a score of trial mixes. “We have submitted over 100 individual mix designs for approval to the various project locations,” says Peter Ney, Technical Manager for Southeast Queensland. In addition, supply on the project has broken production records at two of Holcim Australia’s busiest concrete plants late last year. Brisbane North had a record day in September with 3,303 cubic meters and then a record month in October with 52,663 cubic meters, while the Brisbane city plant also scored a new record for October with 31,209 and then a record day in November at 2,226 cubic meters. 

 


Tunnel boring machines

Mark Taylor, Rhett Duncan, General Manager of SEQ Concrete, and Bruce Thompson, General Manager Sales and Marketing, recently had the privilege of getting up close to the project during a site visit. The trio saw firsthand the impressive tunnel boring machines, or TBMs as they are commonly known, which is the third method used to excavate the tunnels on this project. “These incredible machines are 200 meters long and perform a number of functions at the same time,” says Thompson. “They bore the tunnel, remove the spoil via conveyor, and then place the tunnel lining segments as they go. The two machines will bore two 2.3 kilometer sections of the road tunnel before ultimately being sacrificed under concrete. The infrastructure around the operation of these machines is amazing right down to the need for on-site hyperbaric chambers to deal with workers who may be affected by working in compressed air environments.”

 

Acknowledged competence
The professionalism of SEQ is acknowledged externally: "Our contact persons at SEQ were upfront, proactive and responsive in a most professional manner," says Airport Link major projects director, Lee Price. "They were a credit to their company and that professionalism has flowed on into the delivery of product to the site."

The Airport Link project is scheduled for completion in mid-2012 and will use in excess of 800,000 cubic meters of concrete.