Railways in Melbourne
In February 2015, the State Government established the Melbourne Metro Rail Authority to oversee planning for new twin 9-kilometre rail tunnels through the central city between South Kensington station and South Yarra. The new Metro Tunnel will have five new underground stations and connect the Pakenham and Cranbourne lines with the Sunbury line, creating a new route through the CBD as an alternative to the City Loop. New underground stations will be created at Arden, Parkville, Domain and two new CBD stations, State Library and Town Hall. Enabling works were underway by 2016 and major construction work on the tunnel and stations began in 2017.The project has an estimated cost of $11 billion and is scheduled to be complete by 2025.
Line 3 (Mumbai Metro)
Two 5.2 metre diameter twin tunnels of 33.5 km each will be dug at a depth of 20–25 metres. Seventeen tunnel boring machines (TBMs), each weighing around 1400 tonnes and costing , will be used to dig the tunnels. The TBMs will be lowered through shafts or pits using a specialized crane. Pre-cast segments will be put on the tunnels' diameter to prevent cave ins, after the TBMs bore 1.2 metres. Tunnels will have to be dug through a mix of soil and basalt rock, and is expected to be difficult. TBMs can dig at an average rate of 8 metres per day through rock, and at a rate of 14 metres per day through soil. After TBMs bore through section, the metro tunnel will be lined with pre-cast concrete rings to strengthen the tunnels. Boring and placing rings occurs sequentially. For the entire Metro 3 corridor, around 40,000 concrete rings were cast in 65 moulds. Casting of the rings took place at six casting yards - four in Wadala, one each at Darga, and on the Jogeshwari-Vikhroli Link Road (JVLR). The first concrete ring was fabricated at a Wadala casting yard on 7 March 2017.