One of these machines completed the final subterranean stretch last fall, covering roughly 1,640 feet between two stations on the Central Secretariat-Badarpur line. The TBMs averaged nearly 27 feet a day as they cut through the Delhi silt; while they tunneled, the machines simultaneously installed four-foot-long precast rings that were bolted together to prevent the walls from collapsing.
Before the tunnel can be used, workers will fill and flatten the bottom of the tunnel to lay tracks later on and install electrical connections and ventilation shafts that will extend to the surface.
An undergroud subway in New Delhi? Your going to need serious ventalation if you catch my drift.
Tunnel boring machines are really quite cool, I cant see how this type of construction is any less safe than a tunnel that is built by dinging a trench laying the tunnel and re burring it.
KH, Just because they are in a rush does not mean they are doing it badly. In a country like India...human resource is not a problem. For all you know, they could employ 100s of more people. Its too premature to say how it will turn out.
Seeker72, I caught your drift. It reeks of petty mindedness.
I would be curious to know how the interlocking concrete sections can be adjusted to form a curve in the tunnel. Will anyone familiar with TBM technology please enlighten me? My best guess is that the sections are already cast in specific shapes to fit the intended curve, or maybe spacers are put in for that purpose.
@Marcus, The sections are designed to form a ring, but every single ring is slightly wedge shaped, to go round a curve or slope you stack the thick end of the wedge next to each other etc. for a straight section you stack thick end to thin end. Saw it on the Discovery Channel so I can't claim to be an expert.
@Absolute Wow, thanks for the info, I was just presuming they use wedge shaped rings when they need to turn and normal rings for straight sections. Not bad...
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