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Whatever the cost it wouldn't be worth it. First some lines run within metres of one another so you couldn't expand because there just isn't space. A back of

Whatever the cost it wouldn't be worth it. First some lines run within metres of one another so you couldn't expand because there just isn't space. A back of the napkin plan if you were to go ahead would look like this: 1) Shut down the line completely 2) Remove the tracks 3) Design, build and then get underground some new boring machines which need to be capable of removing the metal lining, digging through earth and concrete then relaying the lining. 4) Rebuild platforms which would inevitably be damaged 5) Relay tracks 6) Design, build and get to London new wider trains Realistically you're looking at 3-5 years (at least) per line to widen them. I don't know if you live in London and are therefore aware how much we Londoners rely on the tube - even if they only widened one line, having it out action for that long would have devastating consequences for communities and businesses and every day Londoners' lives.

bane 12y ago
No, I've only spent a few weeks there. But I did absolutely rely on the tube for most of my transport until I figured out the bus system. Of course it would be horribly disruptive, but it might somebody be a necessity.
avn2109 12y ago
>> "then relaying the lining." Former tunnel boring engineer here. Modern TBM's usually line the tunnel with prefab concrete sectional rings, which are built by a human-controlled hydraulic arm at the front of the TBM's trailing gear, immediately behind the cutterhead chamber. As far as I know, cutting heads that could bore soils/rock could not also bore through metal lining. This is limited by the material properties of the cutting surfaces, typically hard metals or coated ceramics. Heads with acceptable wear rates in hard rock or soils will likely have unacceptably high wear rates against metals. And 3-5 years is probably a drastic underestimate of project duration.

bane 12y ago

No, I've only spent a few weeks there. But I did absolutely rely on the tube for most of my transport until I figured out the bus system. Of course it would be horribly disruptive, but it might somebody be a necessity.

avn2109 12y ago

>> "then relaying the lining." Former tunnel boring engineer here. Modern TBM's usually line the tunnel with prefab concrete sectional rings, which are built by a human-controlled hydraulic arm at the front of the TBM's trailing gear, immediately behind the cutterhead chamber. As far as I know, cutting heads that could bore soils/rock could not also bore through metal lining. This is limited by the material properties of the cutting surfaces, typically hard metals or coated ceramics. Heads with acceptable wear rates in hard rock or soils will likely have unacceptably high wear rates against metals. And 3-5 years is probably a drastic underestimate of project duration.