Excavation has been completed on Cross River Rail's four underground stations: Woolloongabba, Roma Street, Albert Street, and Boggo Road.
The focus is now on fitting out the new stations, part of the $5.4 billion transport project set to come online in 2025.
From working close to existing rail lines to making sure works did not compromise existing residential towers, senior project managers and engineers have explained the complex and mammoth task of excavating the sites in a new video.
Boggo Road station acting senior project manager Kelly Pearson said a special canopy tube system was deployed in the Dutton Park construction project to help reinforce the roof.
"One of the key complexities is the locality — we're building in an urban environment where we've got residents and sensitive stakeholders and the road network directly adjacent to our site," she said.
"Also just the physical real estate that's available for our construction teams for lay down, between cranes and workshops and water treatment plants — real estate is prime.
"Different construction techniques have been used across all the different railway stations due to the locality, or the alignment, that's the geometry of the rail line.
"For example, at the Boggo Road station, the reason we had to use the canopy tubes system, or the umbrella system, is because it's directly located under the Park Road rail line. We just don't have the depth of material above that rail line to physically put in anchors."
Crews are now working around the clock on the Cross River Rail project.
Albert Street intricacies
Albert Street station senior project manager Dusan Ilic explained how the inner city station comprised three "much more constrained" sites along Albert and Mary Streets.
"In lot one, we're digging the biggest hole in the CBD, almost 50 metres deep, and having two 150m towers either side of us, to understand that geotech and being able to provide a design to support the ground is one of those crucial things to understand and be across," he said.
Mr Ilic said with "incredibly hard" ground conditions, a staged process had to be used to excavate the tunnel with road headers and blasting before a tunnel boring machine (TBM) could be used.
Roma Street site to 'transform' city
Under the current Roma Street train station, workers have installed waterproofing and steel fixing, assembled bespoke formwork systems and laid thousands of cubic metres of concrete.
The project's senior project engineer Beau Vidler said the station would "really open up the city".
"The Roma Street station will really transform this area of the city. I think it's really going to open up the city, as we look forward to new infrastructure coming in, as well as the Olympics in 2032," he said.
"In terms of complexities on this job, for the excavation portion, our biggest challenge was making sure we had the cavern excavated and ready to receive the TBMs when they were barrelling down from Woolloongabba.
"We hit quite a few complexities along the way in terms of the ground conditions. The rock we encountered was probably much harder than we anticipated."
Under a new Cross River Rail network plan, south-east Queensland trains will operate in three sections, all connecting at the existing or new underground Roma Street stations.
Existing rail lines will be shifted to reconnect at new or upgraded stations — significantly altering how residents on the Gold Coast and Sunshine Coast access Brisbane.
Sector One will connect the Gold and Sunshine Coasts directly, operating trains from Varsity Lakes and Beenleigh through to Redcliffe Peninsula, Nambour and Gympie.
Sector Two will link the Rosewood and Springfield lines through Central to the domestic airport and Shorncliffe.
Sector Three will run Ferny Grove trains through Central and Southbank to Cleveland.
The new rail plan will shift multiple suburban services, splitting the Ferny Grove line from the Beenleigh line, placing the airport spur along the Ipswich line, and extending the Doomben line from Roma Street to Indooroopilly.
In a major shift, commuters on the Beenleigh and Gold Coast lines will need to change at Boggo Road or Roma Street to access South Brisbane stations and Central station in the CBD.
The Gold Coast and Beenleigh lines will instead travel through the city via Albert Street, Woolloongabba, and Boggo Road.
