Monday, December 14, 2009

Imported tunnel boring machines for underground corridor

Imported tunnel boring machines for underground corridor
S Praveen Dhaneshkar, DHNS

Construction of the underground stretch of the Metro is expected to be very tough to plan and execute. It will involve Tunnel Boring Machines that excavate earth at a depth of 12 mtrs below ground. This will take 36 months to complete and will have seven stations


With the removal of the war memorial statue at Minsk Square on Raj Bhavan Road, the Bangalore Metro Rail Corporation Limited (BMRCL) is on an upbeat mood as it has paved the way for construction of the first station and tunnel on the underground (UG) stretch, which is now behind schedule by more than six months.

The actual construction work is, however, expected to begin only in January 2010, as the BMRCL is yet to award the contract. This massive exercise will involve importing TBM’s or Tunnel Boring Machines to excavate ground by adopting a
‘Cut-and-Cover’ method and will be executed in two stages –– viz construction of stations and boring of tunnels.

The underground stretch runs between M Chinnaswamy Cricket Stadium (Minsk Square) and Magadi Road on the East-West Corridor and between Seshadripuram and City Market on the North-South corridor at a length of 8.8 km.

It will have seven underground stations, including two at the interchange station in Majestic. The UG contract is estimated to cost Rs 2,400 crore approximately.

Re-bidding for tenders

The BMRCL board had recently decided to have the tenders for a stretch of the UG corridor bid afresh, by breaking the tender package into two in a bid to bring down high costs quoted by the participating bidders.

The stretch between City Market-Majestic that will now be rebid is expected to be awarded only in February/March 2010 after completion of financial and technical evaluation of participating bidders.

While two underground stations at the depth of 12 metres and 18 metres will come up in Majestic, one each is proposed at City Railway Station (towards Magadi Road), Chickpet, City Market, Central College, Vidhana Soudha and the Chinnaswamy Cricket Stadium.

According to BMRCL engineers, two tunnels of 5.5 m diameter with a separation of 5 m in between at a depth of 12 m will be built for a distance of approximately 4 km each on East-West and North-South Corridors. The tunnelling process begins from the stadium and ends near Leprosy Hospital on Magadi Road in the East-West Corridor and again begins near Swastik and ends at Makkala Koota Circle in Chamarajapet (K R Road) on the North-South Corridor.

But for the common folks the nightmare of commuting in the vicinity of Minsk Square and along the entire UG alignment could well continue into the next two-three years, as the deadline for completing the UG corridor is 36 months, from the date of contract award.

Until then, road users have to bear with the huge traffic gridlock for almost three years. And mind you, this endurance is subject to the BMRCL completing the construction within the stipulated time frame.

Staffers at the Vidhana Soudha, Vikasa Soudha, GPO, Visvesvarya Towers, High Court and M S Building will bear the maximum brunt of hardships as regular movement of BMTC buses are also likely to be affected along the UG corridor.

Traffic diversions

Minsk Square, a vital link for motorists, connects Dr B R Ambedkar Veedhi, Queen’s Road, Cubbon Road and Raj Bhavan Road. Its full closure, expected anytime soon, will have ripple effects by way of increased traffic jams right upto Manipal Centre and Mahatma Gandhi Road on the eastern side of the City.

The traffic police on their part are prepared with a alternate road diversion plan that proposes, one-lane traffic from Balekundri Circle towards Queen’s statue Circle. A stretch of Cubbon Road from the old Central Telegraph office to BRV parade junction will also face temporary closure.

This diversion will entail movement of vehicles through Cubbon Park, along the Press Club building and Dr B R Ambedkar Veedhi via the State Election Commission office and the old KGID building, using the proposed alternate Road.

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