Multi-mode TBM makes five on Sydney Metro 12 Sep 2019

Jonathan Rowland, TunnelTalk

All five TBMs are now underground and at work excavating the 15.5km City and Southwest extension to the Sydney Metro in Australia. Supplied by Herrenknecht, the five machines include four double-shield TBMs, and a multi-mode machine for excavation under Sydney Harbour, a route that will require boring through a section of Harbour sediment. The specialised machine was the last to begin work, departing from its Barangaroo launch site on the south side of the Harbour in early August 2019.

Multi-mode TBM arrives
Multi-mode TBM arrives

In addition to the twin tunnels, the new Metro line includes six new underground stations: Crows Nest and Victoria Cross to the north of the Harbour, and Barangaroo, Martin Place, Pitt Street, and Waterloo to the south (Fig 1). The tunnels, stations and excavations works package for the project was won by a John Holland-CPB Contractors-Ghella JV in June 2017 at a contract value of AUD$2.8 billion. The contract also includes a launch portal at Marrickville and a temporary TBM retrieval shaft at Blues Point. Bechtel is the Delivery Management Partner for the client, Sydney Metro.

Under a separate contract, Sydney Central Station - located between the new stations at Pitt Street and Waterloo - will be extended underground in a AUD$955 million works package awarded to Laing O’Rourke in March 2018. The AUD$1.3 billion M&E contract for the entire line was awarded to the Systems Connect JV of CPB Contractors and UGL.

Fig 1. New line adds 15.5km to Sydney Metro
Fig 1. New line adds 15.5km to Sydney Metro

Progress of excavations

The first TBMs for the running tunnels launched in late 2018 to excavate the 8.1km section between Marrickville and Barangaroo in the south of the city and on a route that will take them under the central business district. Both have now broken through at Pitt Street Station, a distance of about 6km, after launching in October and November 2018 and boring at a rate of 128m/week and 136m/week, respectively.

To the north of the Harbour, two TBMs are excavating a 6.2km alignment between Chatswood and Blues Point. The first of these machines launched in January 2019, breaking through at the end of a 4.5km drive at the site of the new Victoria Cross Station in late August, after excavating at a rate of 125m/week. After a three week maintenance break at Victoria Cross, it will relaunch to bore the final 1.7km section of the alignment to the edge of Sydney Harbour, where it will be retrieved from a temporary shaft at Blues Point. The second TBM was launched in mid-February 2019 and has bored about 4km at a rate of 124m/week. It is expected to breakthrough at Victoria Cross in September 2019.

City and Southwest route to open in 2024
City and Southwest route to open in 2024

The twin 6m i.d. segmentally lined running tunnels will be connected with cross-passages at 240m intervals.

The multi-mode TBM working under Sydney Harbour can operated in both EPB and slurry modes and will be used to excavate both tunnels under the Harbour. The machine is needed to bore through both the Hawkesbury sandstone bedrock and a reach of Harbour clay, silt, and sediment. Further ground control at the rock-sediment transition zone is expected to be needed and applied using jet grouting. Three barges will be used - one for grout injection processes and two to transport materials between the work area and the onshore facility. The machine launched from Barangaroo in August 2019 and has so far bored about 375m at a rate of 29m/week. At the end of excavation, it will also be retrieved from the Blues Point site.

The underground stations are being constructed using both cut-and-cover, at Crows Nest and Waterloo, and drill+blast, at Victoria Cross, Barangaroo, Martin Place, and Pitt Street. The underground extension at Sydney Central Station is also using cut-and-cover construction (Table 1).

Table 1. Station construction on Sydney Metro City and Southwest line
Station Construction Depth below ground Length
Crows Nest Cut-and-cover 25m 202m
Victoria Cross Drill+blast 31m 270m
Barangaroo Drill+blast 25m 228m
Martin Place Drill+blast 25m-27m 220m
Pitt Street Drill+blast 17m-20m 247m
Central Cut-and-cover 16m 220m
Waterloo Cut-and-cover 25m 200m

The cavern at Victoria Cross is 40% larger than any other station on the Sydney Metro, measuring 270m x 25m x 20m. Three roadheaders were used to construct the cavern, excavating 360,000t of rock. The 228 x 23m x 16m Barangaroo Station is about 88% complete with work underway to secure the ground. In the crossover rail cavern, steelwork, waterproofing and concrete pouring have begun. The Martin Place Station cavern is also almost complete and will measure 220m x 12.4m x 15m. The Pitt Street Station comprises two 247m x 14m caverns set 84m apart. A concrete pile retaining structure was built before excavation of the station shaft areas to support the ground during excavation. Three roadheaders have excavated the station caverns and pedestrian connections.

Of the cut-and-cover stations, the 202m x 24m-26m x 33m Crows Nest Station took 15 months to excavate with large piling rigs and rock bolters installing 225 piles around the edge of the station box to support the ground during construction. Waterloo Station took 12 months to excavate the 200m x 25m x 26m box. Ground anchors and sprayed concrete supported the concrete pile retaining structure during excavation, which was begun by surface miner down to 30m below to the surface.

Central Station

At Central Station, and in addition to new Sydney Metro platforms, the construction contract package includes an underground 19m wide concourse to connect passengers entering from Chalmers Street to suburban rail and Metro platforms and to new light rail and bus services. The Northern Concourse will also be upgraded with new pedestrian thoroughfares and a feature roof.

Alignment under Harbour through sandstone and sediment
Alignment under Harbour through sandstone and sediment

“The upgrade to Central Station represents the biggest improvement to the station in decades,” a Sydney Metro spokesperson told TunnelTalk. “It will make it easier for customers to connect between light rail, suburban and inter-city trains, the Sydney Metro, and buses.”

Construction of the underground metro platforms began in 2018 and is expected to be complete in late 2022. On completion of the Central Station contract, track will be laid along the 30km of the City and Southwest lines and stations fitted out before the start of services in 2024.

“Work to build the metro platforms is happening while Sydney train services continue to run through the rest of Central Station,” the spokesperson continued. “As work happens around them, more than 250,000 customers continue to access train services in Australia’s busiest railway station.”

Sydney Metro development

The City and Southwest extension is Stage 2 in the development of the Sydney Metro, following the opening of the Stage 1 Northwest route earlier in 2019. The current and previous Metro sections will link at Chatswood. Stage 2 also includes upgrade of the existing overground railway between Sydenham and Bankstown to metro standards.

Stage 3 - Sydney Metro West - will extend the service from Sydney city centre to Parramatta and Westmead via The Bays Precinct and Sydney Olympic Park. “The New South Wales Government is committed to delivering Metro West services in the second half of the 2020s with AUD$6.4 billion, allocated over four years, to accelerate construction,” TunnelTalk was told. “The next stage in the planning process is expected to commence by the end of 2019.”

References

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