Following the review, a number of changes to tunnelling procedures have been implemented, including:
- Changes to the pressure in the excavation chamber when excavating in the Ascot formation.
- Continuous operation (no weekend stoppages) especially when tunnelling beneath airport infrastructure.
- Slurry and bentonite quality to be adjusted to reduce potential slurry losses.
TBM Sandy will also restart operations prior to the end of April. It is commonly accepted best practice that two TBMs are not located side-by-side underground, so once Grace has progressed a safe distance ahead, Sandy will recommence her underground journey.
Airport Central Station has been prepared for the TBMs to arrive next month. This will be the first time the machines 'surface' since tunnelling began in Forrestfield last year.
Airport Central ready for TBMs to arrive
The TBMs will enter the Airport Central Station box via mass concrete false blocks, used to stabilise the walls and reduce water ingress.
2200m3 of concrete was poured over four sessions to create the false blocks. Once the TBMs have tunnelled through the blocks and into the station box, they will remain at Airport Central Station for several weeks for maintenance.
Construction of the base slab at Airport Central Station is also complete, with the six base slab sections totalling approximately 6000m3 of concrete, 4130sqm of waterproofing and 1600T of steel reinforcing.
Bayswater Junction takes shape
Diaphragm wall construction continues at Bayswater Junction, with more than 100 of the required 133 wall panels completed and the remainder due to be finished by the end of the month. Shallow excavations have now started and dewatering will soon begin to allow deep excavation within the tunnel portal and dive structure. Installation of monitoring and recharge wells for the dewatering process has begun. When complete, the dive structure will be more than 400m in length and provide the entry/exit point to the tunnels for trains.
The retaining wall built last year along Railway Parade to accommodate track works is getting a makeover. Perth urban artist Drew Straker and PTA's Right Track are working on the mural, which is inspired by WA landscapes.
Bayswater Station to be revamped
Bayswater Station will become a major transport hub with the Forrestfield-Airport Link and the proposed Morley-Ellenbrook rail line connecting to the Transperth network at that point.
To reflect its importance as an interchange station and heart of the Bayswater town centre, the station will undergo a major upgrade. Also additional rail infrastructure will be built between Bayswater and Meltham stations.
For more information on the station upgrade, how you can have your say on the station design and how to stay updated, visit the METRONET website.
Excavation continues at Redcliffe Station
Excavation has been progressing at the Redcliffe construction site, with 60 per cent (26,800m3) of spoil removed. Excavation will be completed later this month, after which works will turn to pouring the concrete for the base slab of the station box.
Dewatering will be turned off once the base slab is finished around late August 2018.
Road works around Forrestfield Station
Foundations for the Dundas Road realignment are 75 per cent complete, with more than 200m of drainage lines installed. Intersection works, which will connect the new road to the current Dundas Road, will commence within the next two weeks.
Once the realignment is completed and open to traffic in mid-2018, the current Dundas Road will be closed south of Maida Vale Road and north of Imperial Street.
View a map of the changes to Dundas Road.
Construction of the retaining wall for Forrestfield Station is also progressing with 81 of 92 panels in place. Backfilling undertaken to date has raised the ground level in some areas by 5m.
Emergency egress shafts
Works have begun to connect the first of three emergency egress shafts (EES) to the tunnels. At the EES off Abernethy Road a 2.1m circular saw is being used to cut through d-walls ahead of excavation of the cross passage.
Jet grouting is continuing at the Wright Crescent EES to stabilise the ground ahead of the cross passage being constructed between the tunnels and the EES. The process will continue for another two months, after which works will shift to the excavation of the egress shaft.
At Airport West EES, excavation of soil within the shaft is now 40 per cent complete. Excavation will continue over the coming months until the required depth of 34m is met.