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0 pointstonyhb11y ago0 comments

And the Hong Kong MTR was designed by the same architect that worked on some of London's line extensions. They had a huge amount of experience and learnt lessons to pull from over the hundred years London's underground had been running.

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NickPollard11y ago· 1 in thread

Also, I don't know what Hong Kong is like, but London has been a major city for about 2000 years, and under the surface contains not only rail lines, but sewers, tunnels, underground rivers, burial pits, bunkers, luxury belgravia basements, and the detritus of two millennia of occupation.

Trying to dig anything under London now is a huge effort because of all this.

This is very much a 'move slow and try not to break anything' environment.

gsnedders11y ago

Case in point: the Crossrail tunnel through Tottenham Court Road has about 85cm clearance both above and below it, and had to be constructed with the Underground tunnels around it still in active service.

Building new lines through relatively soft clay is really hard when you have hundreds of notable historical buildings that you cannot afford to have any subsidence (like, millimetres is enough to cause really damage), and then when you don't really even though where half the other underground pipes are exactly (many of them are hundreds of years old, and some we simply don't know exist)… It's a real challenge.

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