Free Press Journal

Metro 3 will make Mumbai, India’s second city to have under water tunnel

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After being in government’s pipeline for many years Metro 3 or Colaba-Bandra-Speez Metro corridor, finally started its work in December last year. After being the first underground Metro corridor in Mumbai, it is the second city after Kolkata in India to have a underwater metro rail corridor. The Mumbai Metro Rail Corporation (MMRC) will need a expertised contractors and consultants, for making this under water metro rail corridor. The 1.2km patch of the rail corridor which will go from under the Mithi river between Bandra Kurla Complex and Dharavi stations.

The city’s first underground metro corridor that would connect Colaba with SEEPZ via Bandra will have trains with eight coaches and not six because the Mumbai Metro Rail Corporation (MMRC) has estimated a surge in the number of passengers if the project is completed by 2020. Metro 3 also referred as Colaba-Bandra-Seepz Metro, is a part of the metro system for the city of Mumbai. When completed, the 33.5-km long line will be the first underground metro line in Mumbai. The metro line will connect Cuffe Parade business district in the extreme south of the city to SEEPZ in the north-central with 26 underground and one at-grade station. The cost of this corridor is estimated at Rs 23,136 crore.

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As reported by Indian Express, an MMRC official said that the some water drippage during constructing this 1.2km line will happen, due to rocks here are weak making tunneling a major engineering challenge. Decisions will be taken on spot by the engineers and designers with geologists which will be present at the site. Certain special measures will also be taken during excavation to safeguard against challenges. These include strengthening the weak and broken rock to improve the geological structure and reducing the permeability.

Tunnel Boring Machines (TBM) will excavate the mainlines. TBM are huge machines that will be lowered at some distance from the river with the help of a heavy duty crane through shafts and will drill twin tunnels below the riverbed. And the New Austrian Tunneling Method (NATM) will be used for two tunnels for the stabling line and connecting it to the main line. NATM technology is generally used to create tunnels of smaller lengths. NATM technology will be used for the first time underwater.

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Special measures will also be taken during excavation, which includes strengthening the weak and broken rock to improve the geological structure and reducing the permeability. From a depth of 12-13 metres from the river bed a stabling line will be laid. This line will be used for stabling and reversing of trains which will end at the BKC station. MMRC has chosen BKC station for the stabling line due the bigger space and less amount of traffic. The construction of this 1.2km rail line faces major challenges, MMRC assures that after completing the construction it will be safe to travel.