India’s First Undersea Tunnel In Mumbai – Free PDF Download


What has happened?

  • Come 2023, Mumbai will be home to India’s first undersea tunnel, which will be part of the the city’s Coastal Road

Where are Mumbai’s undersea tunnels being built?

  • The twin tunnels, which have a length of 2.07 km of which a kilometre will be under the sea, are being built,
  • As part of the Mumbai Coastal Road Project, a58-km stretch starting from the Marine Drive promenade to the Worli-end of the Bandra-Worli Sea Link.

  • The road, which will comprise of land-filled roads on areas reclaimed from the sea, bridges and tunnels,
  • Is part of a plan to link South Mumbai with North with a toll-free freeway that is expected to ease up traffic in one of the most congested cities in the world.
  • It is the first undersea road tunnel in the country which will pass through Arabian Sea near Girgaon Chowpatty.
  • It will start from Priyadarshani Park and end at Netaji Subhash Road in Marine Drive.

How deep under the sea will these tunnels be built?

  • Unlike the big undersea tunnels in the world, include the Channel Tunnel that connects England and France,
  • The twin tunnels in Mumbai are being built at a relatively shallow depth.
  • Mumbai’s undersea tunnel will be 20 metres below the seabed.
  • In comparison, the Channel Tunnel at its deepest point is 75 metres below the sea bed.
  • The Seikan Tunnel in Japan lies over 100 metres below the seabed.
  • The Mumbai tunnel is also being built very close to the coast, where the depth of the sea is not more than 4 to 5 metres.

How are the undersea tunnels being dug?

  • A 2,800 tonne tunnel boring machine, the biggest of its kind in India, has been deployed to dig these tunnels.
  • An 18 metre shaft has been dug at Priyadarshini Park to lower the machine below the ground from where it will start boring through the strata.
  • The machine, which is operated by a team of 30 people, has a diameter of 12.19 metres which will bore through solid rock.

  • Tunnel boring machines are used as an alternative to drilling and blasting methods in rock and conventional “hand mining”.
  • TBMs have the advantage of limiting the disturbance to the surrounding ground and producing a smooth tunnel wall.

major challenges of building the tunnel?

  • The fact that parts of it are being built under sea makes the construction a significant challenge.
  • The two primary issues of concern are the seepage of sea water into the tunnel and the fear of the tunnel caving in due to the pressure exerted by sea water.
  • The fact that the tunnel is very close to the coast and not in mid-sea has made things easier for engineers.

How will temperature be regulated inside tunnel?

  • The tunnel is basically a confined space and requires ventilation to ensure a tenable environment for users.
  • The fact that these tunnels are under the sea makes the dispensation of carbon monoxide which is emitted by cars a difficult proposition.
  • High levels of carbon monoxide inside the tunnel could be hazardous for commuters.
  • To tide over the problem of flushing out these hazardous gases from inside the tunnel system,
  • A first of its kind ventilation system called Saccardo will be installed inside the tunnel.
  • The system monitors the emission levels inside the tunnel and shoots an air jet through large ventilation fans to drive out the fumes in the desired direction.

Cost And Time?

  • The total cost of the stretch from Priyadarshini Park to Princess Street Flyover at Marine Drive of coastal road,
  • Which mainly includes construction of tunnels and other allied works, is Rs 2,798.44 crore.
  • Each tunnel will take about 8 to 9 months to finish.
  • The BMC said that work for both the tunnels will be completed in about two years.
  • Drilling for south bound traffic tunnel has started and after completion, the TBM will be removed near Marine Drive and then transported back to Priyadarshini Park for drilling second time for north bound traffic.

Q) India has excessively relied on toll collection for the construction of highways.

The toll collection model is similar to which of the following model of private-public partnership?

  1. Design-built-finance-operate
  2. Built-lease-transfer
  3. Built-operate-transfer
  4. Built-own-operate




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