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28 Jun 2022, by Amy Sarcevic
As Brisbane gears up to host the 2032 Olympic and Paralympic Games, millions of dollars are being funnelled into new infrastructure projects throughout the city, and nearby suburbs across South East Queensland (SEQ). One of the most prominent of these is the Cross River Rail project – a 10.2 km rail line from Dutton Park to Bowen Hills, including a 5.9 km stretch of twin tunnels under Brisbane River and the Central Business District (CBD).
Cited by State Premier Annastacia Palaszczuk in her address to the International Olympic Committee as a key reason why Brisbane was a suitable host for the games, Cross River Rail is believed to have played a key role in helping Brisbane secure the Olympic deal. The project – which includes four new Brisbane underground stations, two station upgrades, six station rebuilds, three new Gold Coast stations, and a world class signalling system – will improve access to at least four venues earmarked for Olympic events.
Chief Executive Graeme Newton says the project – which currently employs more than 2700 workers and has provided opportunities for 1700 local suppliers and subcontractors and 315 apprentices to date – will play an equally key role in boosting the city’s economic recovery in the aftermath of COVID-19.
“Cross River Rail is more than just a rail project. It is a critical public transport infrastructure project that will improve our quality of life, help our economy keep growing, generate thousands of jobs, and activate urban development across the whole region,” said Mr Newton ahead of the Urban Rail Conference, hosted by Informa Connect.
“It is also a catalyst for wider rail transformation – a fix at core of rail network that makes a number of possible future rail improvements across SEQ more viable. Ultimately, journeys will be quicker, stations will be in more convenient locations, and greater passenger volumes will be accommodated.”
Overcoming geotechnical hurdles
Currently the project is progressing well, with a 3.8 kilometre stretch of twin tunnels excavated beneath the Brisbane River and CBD – from Woolloongabba to the project’s Northern Portal – and 900 metres from Woolloongabba to Boggo Road.
However, Mr Newton admits this work has not been without challenges. Tunnelling under the river was a particular issue, he says, with the site known for its complex geology. Here, tunnel boring machines (TBM) were pivotal in determining – and allowing for varying degrees of – rock strength.
“The TBMs undertook probe drilling to assess geology and changed the way their shields were used to excavate more safely in areas of lower rock strength. Systems in place on the machines and the tunnel design itself also ensured tunnels were watertight,” Mr Newton said.
Work at the Albert Street site was also a challenge. Akin to “key hole surgery” in the inner city, excavation at this site had to extend 50 metres below ground, making it the deepest hole ever excavated in Brisbane.
Given the significant depth, 19 steel propping beams, each weighing 50 tonnes, had to be installed in the station box to ensure the stability of excavation and nearby buildings. Significant rock anchors were also needed – some over 30 metres long. Meanwhile, traditional excavation techniques, like hammering, had to be complemented with drilling and blasting, given the rock strength. All of this work taking place in a busy CBD environment.
“There was a lot of focus on keeping stakeholders happy across progress and works. For example, at Albert Street we excavated a 290-metre-long station cavern up to 34 metres underground; all the while people were walking through CBD with no idea of work beneath their feet,” Mr Newton said.
“Meanwhile Boggo Road was next to a research facility with sensitive instruments and heavy traffic inflow. It was delicate work trying to minimise the amount of traffic and keep the work progressing at a suitable pace.”
Constraints at Boggo Road also required specialised techniques. Each piece of equipment had to be lowered down into the 27-metre-deep station box by crane, including other cranes used in the station box. “Two of the strongest tower cranes in the world were used for this purpose – each capable of lifting 330 tonnes each, equivalent to 47 African elephants,” Mr Newton said.
The project’s southern portal was one of the most challenging aspects of the project. It required a new rail line to be threaded through what is already a congested and complex corridor.
“It was a challenge to build a tunnel portal and connect to the rail network with the least amount of disruption. We went from a split portal structure to single cut and cover structure – where both tracks went down into the same tunnel. We then realigned tracks at Dutton Park station. All of this meant working closely with Queensland Rail and contractors,” Mr Newton added.
Finally, the recent flooding presented some issues.
“We had some impact – not a catastrophic one, but with volume of rain, we had to manage water on some sites. Thankfully, our team did a fantastic job in doing that.”
Looking ahead
With the 2021 “year of tunnelling” now complete, Mr Newton and team are looking ahead at the next project phase.
“The focus this year is on tunnel fit-out and stations taking shape, given that we now have huge underground caverns and station boxes fully excavated. I’m proud of what we have achieved so far and am looking forward to seeing the construction of these steam ahead.”
Hear more from Graeme Newton at the Urban Rail Conference hosted by Informa Connect. This year’s event will be held 18-19 July at the QT Gold Coast.
Learn more and register your place here.
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