By Lynda Myer
The tunneling and digging process on the Sydney Metro City and Southwest project in Australia, has been completed by John Holland CPB Ghella joint venture.
Delivery of a key section of the city-shaping Sydney Metro project by this joint venture done after four years of works.
In order to bore 15.5km of twin tunnels in the Sydney Metro City and Southwest tunnel and station excavation project, five tunnel boring machines (TBMs) were mobilized.
While the route beneath the Sydney central business district (CBD) toward the southwest hosted four Herrenknecht Double Shield machines to excavate 14.5km of twin tubes with 6.96m diameters, the tunnel below the harbour with 900m length and 7.04m diameter, was dug using a Herrenknecht Mixshield machine due to the heterogeneous geology and high water pressure in this section.
The 99,000 tunnel lining segments for the project were manufactured at a pre-cast facility at Marrickville.
The other responsibilities of joint venture in this project involve:
- Creating two permanent dive portals at Chatswood and Marrickville in order to start up TBMs at either end of the alignment.
- Providing comfort excavation and permanent lining of the station caverns by implementing access shafts at each of the three mined stations at Victoria Cross, Martin Place, and Pitt Street.
- Three open-cut stations at Crows Nest, Barangaroo, and Waterloo.
- A crossover cavern at Barangaroo with fully concrete lining that involved eliminating 650,000t of crushed rock.
- 57 cross passages at 240m intervals.
- A temporary retrieval shaft at Blues Point, on the north side of the harbour for the two TBMs that completed the northern drives, as well as the under harbour TBM.
The expansion of Sydney Metro City and Southwest will be 30km of metro rail and will stretch from the end of Metro-North West Line at Chatswood beneath Sydney Harbour, through new CBD stations and southwest to Bankstown. The inauguration date of seven new metro stations and 11 upgraded stations is 2024.
