News Articles | 25 October 2018

TBM Grace has made good progress in the last month and has now tunnelled 44 per cent of the entire tunnel length between Forrestfield and Bayswater Junction.

She has successfully tunnelled under the main runway and is expected to reach Redcliffe Station early next year.  

TBM Sandy is just under 500m behind Grace, and is currently stopped for scheduled cutterhead teeth replacement before recommencing tunnelling. Together the machines have installed almost 21,000 tunnel segments.

While the TBMs are progressing well, the recent leak at the project's first tunnel-to-tunnel cross passage requires ongoing assessment and repair. Jet grout was injected into the ground late last year in preparation for the cross passage to be constructed. In this instance, a leak occurred during construction allowing groundwater and silt to flow into the cross passage and one of the tunnels. As a result, a sink hole formed at the surface above the cross passage, about 200m north of the Forrestfield Station site where the tunnels follow the alignment of Dundas Road. The leak has now been stopped and efforts have shifted to repairing damage caused by the leak, including the reinstatement of Dundas Road.  

Main focus on excavation at Bayswater 

A few changes have occurred at Bayswater Junction in the last month. A new piece of work has commenced at the dive portal, where construction of the dry box is now in progress. The dry box will be the final structure the TBMs have to tunnel through in order to resurface at the Bayswater dive structure. 

As part of the dry box construction, piling work is currently being undertaken between the dive structure and the existing principal shared path (PSP), used by both cyclists and pedestrians at Guildford Road. The works are scheduled to finish within the month and some localised stop-and-go traffic management will be implemented outside of peak periods. All cyclists should approach the area with caution.

Excavation of the 400m long dive structure is ongoing with the Midland Line overpass now fully excavated and water blasting of the d-walls underneath the overpass in progress.

Forrestfield Station taking shape

Forrestfield Station is starting to take shape with the construction of the station’s platform foundations now in progress. The island platform will be 150m long, 11.5m wide and will help move an estimated 9800 passengers to and from the new station daily.

Installation of the southern retaining wall is on track. At the same time, excavation of the stowage area is taking place to enable hydraulic services (water, sewer and fire) to be installed. The stowage area is the northern most area of the station and will be used for servicing and cleaning of trains. It is planned that brick and steel works to construct the stowage building will start by the end of November.

Backfilling of the station retaining wall is progressing well, with the closed section of Dundas Road now fully covered. Once finished, the ground level will have been raised by six metres to form the at-grade entrance to Forrestfield Station.

Redcliffe base slab pours nearing completion

Construction of the base slab at Redcliffe Station is now more than halfway complete with the fifth of nine pours finalised. There will be two additional pours in October, with the final two due for completion by the end of November. An up-to-date schedule of pours can be found on the project website.

The 1.5m deep slab will then be prepared for the arrival of the tunnel boring machines (TBMs) later this summer. Works will include construction of columns and removal of temporary struts.

By the time the TBMs reach Redcliffe Station they will have constructed 1573 rings over 2517m since departing Airport Central Station.

Rings and columns at Airport Central Station

Infrastructure works at Airport Central Station continue with the casting of the final column to support the different levels within the station box. Construction of the elevator pit has commenced, as has construction of the elevated walkway which will be part of the main station entry portal.

A milestone was reached earlier this month with the completion of the first staircase for the station.

In progress is work on the ring beams for the eastern end of the station box. These are circular concrete structures connecting the tunnel segments and diaphragm walls, providing a waterproof seal at the tunnel entry and exit. The first concrete pour is currently curing.

Emergency egress shafts on track

Emergency egress shafts (EES) provide emergency exit points for passengers along the tunnel alignment. In the event of an incident, commuters will access the EES using the cross passages and walkways within the tunnel. They will then be able to use either the stairs or the lift contained within the EES to reach ground level.

All three EES - Abernethy, Airport West and Wright Crescent - are currently at different stages of construction.

Excavation of the shaft and construction of the base slab for Abernethy EES are complete and focus has shifted to installing the permanent electrical services which will support the building on top of the shaft.

At Airport West EES the base slab is ready to be poured with steel reinforcement installed and concrete due to be pumped to the 35m deep base of the shaft in the coming weeks. Work will then stop for a short period of time to allow wet curing of the concrete.

Last, but not least, excavation at Wright Crescent is almost at the halfway mark, with 16m of 34m complete.

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