CROSS RIVER RAIL | PROJECT
“The spoil goes by conveyor belt back to an acoustic
shed, again at the Woolloongabba site. From there it is sent by truck to various construction locations including Brisbane Airport and the Port of Brisbane.” Luong’s remit includes the Woolloongabba station
cavern. “Station shaft sizes vary between the four new underground stations” he says. “On average, they are around 30m below ground level. The caverns are 280m long, except at Albert Street where it is 10 metres longer. They are an inverted ‘D’ shape, about 15m high and 23m wide. “The temporary retention structures for all the
station boxes have been constructed with soldier piles supported by stress anchors. The drop shafts, also temporary, are primarily being used for removal of the excavated cavern spoil by kibble crane.” The Boggo Road cavern is less deeply buried than the
others. Its roof lies just below the surface under existing public transport infrastructure, including above-ground rail lines. For this reason, canopy tubes were installed to reinforce the cavern roof. Before excavation, 19 steel tubes were drilled horizontally in an arch shape to form a pipe umbrella. Each tube was 506mm in diameter and 102m-long; once inserted they were filled with grout. The cavern was then excavated beneath the resulting concrete arch, which gave additional support to the roof. Part of the Albert Street cavern was in fact excavated
by TBM. In June 2021, TBM Else tunnelled beneath what had so far been excavated of the cavern. It carried on through and once it was clear the cavern excavation team blasted their way down to the tunnel, completing the lower section of the cavern. The advantage was that the TBM itself had excavated a good proportion of the cavern’s final cross-section – about a quarter of it in fact – which meant in turn that the spoil from that section was sent by the TBM’s conveyor back to the Woolloongabba portal, instead of having to be craned out and trucked through the inner city. Around 2,000 truck movements were saved. Altogether, the TBMs will mine around 290,000m3
of spoil. “The traverse below the Brisbane River has been one
of the project’s most challenging aspects so far,” says Luong. “The stretch under the Brisbane River is about 400m long, and 42m below the river. While they were tunnelling beneath the river, crews undertook probe drilling around 35m in front of the TBMs, which allowed our workers to determine what type of geology they would be passing through. The TBMs can change to single-shield mode, which allows them to excavate more safely in areas of potentially low rock strength, and there are systems in place to ensure that the machines and tunnels are watertight. Our lead TBM, Else, was able to complete her tunnel under the river in about three weeks. That was a massive milestone for the project.”
USING RECYCLED GLASS An interesting initiative on the project is that it is trialling a type of sand made from recycled glass as pipe-bedding fill for stormwater pipe relocation works. The first trial was at the Boggo Road site in 2020, and
mat2.indd 1
a second trial at Mayne Yard has also proven to be a success. The crushed recycled glass is used in the same way as any other sand or aggregate. Because the glass has been reduced to the granular size, shape and consistency of normal sand it does not cut hands or cut into pipes. This sustainable method reduces the amount of glass
ending in landfill and also reduces the amount of sand or gravel from excavation. Cross River Rail will use around 10,000t of the material, which represents about a quarter of the glass sent by southeast Queensland to landfill each year. “As of September 2021, TBM Else has travelled 3,017m,
and TBM Merle has gone 2,614m,” says Luong. “Both have passed through the Roma Street cavern and have begun the final leg of their journey to the northern portal at Normanby. TBM progress has averaged around 20 or 30m per day, and both machines are expected to break through at the northern portal by the end of the year. “And the roadheaders have excavated the rest of the
twin tunnels from Woolloongabba south to Boggo Road. The project so far is on course for commissioning in 2025.” That should be in plenty of time to prepare for visitors to the 2032 Olympic Games, assuming we have no more disruptions from an erratic pandemic.
MAT HELLAS VENTILATION DUCTING S.A is specializing in manufacturing and exporting various kinds of Flexible Ventilation Ducting. Having four decades of experience, the company has supplied ventilation systems to many tunnelling and mining projects to over more than 40 countries worldwide.
according to European Directive 94/9/EC.
Kompoti, Arta Epirus, Greece
Postal code: 47040 /
P.O.BOX: 416
Phone: (+30) 26810 26455 Mobile: (+30) 6946844648
www:
mathellas.com Email:
info@mathellas.com
November 2021
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