Queensland's LNP opposition has called for the $5.4 billion Cross River Rail project to be renamed after the late Queen Elizabeth II.
LNP leader David Crisafulli said it was "only fitting we honour her service" as he launched a petition for the name change on Wednesday.
"Queenslanders across our state have loved and admired Queen Elizabeth II," he said.
"Today we launch a petition to rename Cross River Rail, Queensland's first underground rail line, to the Elizabeth Line.
"This is a once-in-a-lifetime opportunity for Queensland to forever honour her life and legacy."
But Queensland Treasurer Cameron Dick accused the opposition of harvesting petitioners' data.
"Why are they hosting a petition on a party political website, why are they not using a parliamentary petition?" he said.
Mr Dick said it was disrespectful to launch the petition on such a website before the monarch's funeral.
Meanwhile, a complex mix of design and engineering principles continue deep underground on the project.
Stretching from Dutton Park to Bowen Hills, Cross River Rail is a new 10.2-kilometre line that includes 5.9km of twin tunnels under the Brisbane River and CBD.
The project is scheduled to be completed in 2024 and operational in 2025 after testing and safety checks.
These engineering feats are making it all possible.
Underpinning
Underpinning is the method used to ensure the project team can tunnel safely beneath the inner northern busway at Roma Street while buses are still running over it.
It was also used to tunnel under the freight flyover, which takes freight trains off the suburban track straight to the port, near the Boggo Road site.
Cross River Rail senior project engineer Yasmine Eldin said underpinning was "a transfer of load from one structure to another".
Ms Eldin said the bridge footings for the freight flyover had to be demolished to allow excavation to create the Boggo Rd site.
"We set hydraulic jacks, fixed them on top of those beams to lift the weight of the bridge up, we then grouted those beams to the existing structure, and lowered the jacks," she said.
"Once we let the jacks go, the weight of the whole bridge support structure now sits on the new underpinning structure."
Twisting, lifting beams
Installing the mezzanine levels of Cross River Rail's underground stations — the last level before passengers take an escalator down to the station platforms — uses a "world-first method of construction", according to a project spokesman.
The engineering team is twisting and lifting 180 beams weighing 70 tonnes within station caverns to put them in place, with only millimetres to spare on each side.
Queensland Deputy Premier Steven Miles said it was "the engineering equivalent of keyhole surgery, or a ship in a bottle".
About 458 individual segments are being cast to make the mezzanine beams at Woolloongabba.
Up to three segments are used per beam.
Way down below
The project's Albert Street station box now holds the title for deepest hole excavated in Brisbane.
Reaching 50 metres below ground, crews generated more than 47,000 cubic metres of spoil while excavating the hole, which will house the first new train station in Brisbane's CBD in 120 years.
Twin tunnels
Twin tunnels 5.9 kilometres long now stretch from Dutton Park to Bowen Hills under the Brisbane River and CBD.
The massive excavation task, which used 165-metre-long tunnel boring machines and 115-tonne roadheaders to remove more than 400,000 cubic metres of spoil was completed at the end of 2021.
Jumpform construction
Cross River Rail's Woolloongabba station is being built using the jumpform method.
It is a self-supporting method of concrete construction where each level is built on top of the last.
"The method has helped crews build the future transport hub up from the bottom of Woolloongabba's 33-metre-deep station box, with the highest point now 21 metres above surface level," a project spokesman said.
