Tunnelling was operational for most of the Christmas period and both TBMs have now cleared the airside environment and passed the 25m-deep Airport West emergency egress shaft.
Despite this progress there has been a recent set back to tunnelling, with both TBMs stopped after workers operating TBM Grace reported a potential mechanical issue just short of reaching the 4km mark. Since then damage to the screw conveyor, which moves excavated material away from the front of the TBM, has been identified. As a precautionary measure TBM Sandy was also stopped and inspected, confirming hairline cracks in the same part of the machine.
It is estimated that repair works will be completed late-February, after which the TBMs will continue their underground journey. Two new screw conveyors are currently being manufactured and will be fitted once Grace and Sandy have arrived at Redcliffe Station later this year.
Multiple work fronts at Bayswater Junction
After completing the construction of the base slab for the Midland Line overpass in the second half of 2018, focus has now shifted to the southern retaining wall. Once poured and cured, the 160m-long wall will be backfilled with 4800 cubic metres of soil excavated from the dive structure. The finished construction will enable the city-bound Midland Line to cross over the Forrestfield Line.
Excavation of the dive structure is ongoing and 85 per cent complete. To date, more than 50,000 tonnes of soil have been removed.
Meanwhile in the areas where excavation has reached the required depth, construction continues on the base slab for the 400m-long dive structure. Given the length of the structure, 18 separate pours are required, totalling more than 4000 cubic metres of concrete. Due to the complexity of each pour, some out of hours work will be required. A schedule of pours is available on the project's website.
Later this month the now redundant main drain pipes, replaced by new pipes laid by a micro-tunnelling machine mid last year, will be removed.
Other upcoming works include the construction of the second and third retaining wall for the principal shared path (PSP) along Whatley Crescent, followed by preparation works for the construction of noise walls.
Forrestfield Station taking shape
Forrestfield Station is starting to take shape with the construction of the station’s platform and concourse levels now in progress.
Both platform foundation walls have been completed, as have the escalator and lift pit walls. Backfilling has commenced while hydraulic services installation is being finalised.
At concourse level, five of seven separate concrete pours have been completed for the station’s 130m-long concourse slab. The slab is expected to be finalised by the end of March, by which time a total of 300 cubic metres of concrete will have been poured. Installation of steel, to form the station roof, will commence shortly.
South of the station, brickwork has been completed on the stowage building where trains will be stored and maintained when not in use. Pre-cast concrete piers, which create the stowage platform, are currently being installed.
At the northern end of the site work on the portal building is progressing well with plans to start installation of building services in the next few weeks. Casting of the main slab for the portal building will follow along with construction of lift and stair shafts. The portal building houses the controls to operate and maintain the tunnels.
Works to reinstate Dundas Road, following the incident that occurred at the first tunnel-to-tunnel cross passage in September, have been completed. Survey works have begun in the area to identify any underground infrastructure that needs to be considered while planning of the final road design for the station's precinct is undertaken.
Finishing touches for TBM arrival at Redcliffe
Preparation works continue for the arrival of the TBMs, including construction of in-situ double segment blocks. These will support the TBMs and their 130m-long trailing gantries to be manoeuvred through the station box to where the cutterhead is to be lined up for the next section of tunnelling.
Of the 20 columns being constructed throughout the station to support the ground slab above, twelve have been completed and another eight are scheduled to be installed once the TBMs have left the station box.
Later this month works will begin at the site located behind Central Avenue and Second Street homes, with a new boundary fence and the foundations of the car park scheduled to take approximately three months to complete.
The finishing touches (line markings and landscaping) will not be added until later in the construction program. In the meantime, the area will continue to be fenced off, as it currently is, and used as a laydown area when required.
Adding height to Airport Central Station
While the majority of construction is located underground, a structure of height has appeared at Airport Central Station recently. The building forms the entry to the Skybridge, which will provide passengers with an undercover connection between the train station and terminals.
Learn more about the Skybridge here.
There are two remaining sections of the 150m-long concourse slab to be poured before works are completed. This includes the final section on the eastern end of the station box, which is already underway, and the final section on the western side, which will be completed mid-year.
The new year has also seen construction commence on the second of nine staircases. Once complete it will connect platform and concourse levels as part of the station emergency escape routes. Works on the seven remaining staircases to be built throughout the station will begin in the coming months. Two of these staircases will be accessible by the public and the remainder will be used for a combination of staff access and emergency egress.
Emergency egress shafts fully excavated
After waterproofing was completed at the Abernethy Road emergency egress shaft (EES), the permanent concrete between the tunnels and the shaft was poured late last year. Construction of the staircase, lift shaft and ancillary building will commence in April.
The buildings located on top of each shaft house communications, electrical and mechanical equipment, and controls. They also contain air vents which will help ventilate the shafts and tunnels.
The base slab for the Airport West EES has been completed. Excavation of the cross passages, which connect the shaft to each of the tunnels, is due to start in the coming months. Works involve excavation utilising temporary steel frame supports, followed by waterproofing and construction of a permanent reinforced concrete lining.
Excavation of the 39m deep Wright Crescent EES in Bayswater was completed late last year. Approximately 2500 tonnes of soil were excavated from the shaft. With this complete, activity has now turned to waterproofing the base in preparation for the base slab concrete pour.