LU - Why Victoria Line was built in deep tube size though it was a new project during WWII

[Ken H]

Any civil engineer will tell you that a principal driver of cost of tunneling is ... what sort of strata you are tunneling through.

And London has the blue clay. The ideal tunneling materiel.
Which is why many other metros are cut and cover.

Berlin, for instance, is largely built on waterlogged sand. So very difficult to tunnel in. So much of the U-Bahn is cut and cover or even elevated.

 

[Dr Hoo]

Surely Crossrail 2 (which has been paused anyway) was mainly intended to relieve the suburban heavy rail routes in Waterloo in its final incarnation. And, to a lesser extent, the Lea/Lee Valley.
The nature of London and its wider commuter belt has changed vastly since the 1940s. A larger diameter Victoria wouldn’t have helped Wimbledon very much IMHO.

 

[Taunton]

And London has the blue clay. The ideal tunneling materiel.
Which is why many other metros are cut and cover.

Berlin, for instance, is largely built on waterlogged sand. So very difficult to tunnel in. So much of the U-Bahn is cut and cover or even elevated.

Engineer on HS1 where it passes under the Thames at Dartford said it was like tunneling through a blancmange!

 

[Helvellyn]

And now, thanks to Victoria Line was build as tube size, we now need to think of Crossrail 2.

But Crossrail 2 started life as the Chelsea-Hackney line, taking over the Epping branch of the Central and the Wimbledon branch of the District.

 

[hkstudent]

But Crossrail 2 started life as the Chelsea-Hackney line, taking over the Epping branch of the Central and the Wimbledon branch of the District.

But at the end, the northern branch need to diverted to Lea Valley Line which means that what supposed to be used with "Victoria Line" has to be covered by Crossrail 2.
If wasn't Victoria Line built like that, Crossrail2 can go elsewhere

 

[coppercapped]

But at the end, the northern branch need to diverted to Lea Valley Line which means that what supposed to be used with "Victoria Line" has to be covered by Crossrail 2.
If wasn't Victoria Line built like that, Crossrail2 can go elsewhere

The Victoria line was planned and built as a route within London as was one of the other early concepts, the Chelsea to Hackney line as mentioned by Helvellyn in post #64 above.

Only after Thameslink was being planned by BR in the early 1980s to connect suburban routes north and south of the city centre and seeing the examples of the RER in Paris and S-Bahn extensions in Germany (especially Munich) which also connected suburban routes on each side of their respective cities did the Chelsea-Hackney concept morph into Crossrail 2 using mainline sized trains and being extended to take over services on the inner suburban routes radiating from Waterloo and Liverpool Street.

It's also not a case of one or the other or even of making poor decisions 60 years ago as seems to be the suggestion. Elsewhere RERs and S-Bahnen coexist quite happily with Métros, U-Bahnen and trams within the same conurbation, each serving different areas, needs and demographics.

 

[AlbertBeale]

Yes that’s right, to give cross platform interchange in the same direction. Also existing station platforms and tunnels were included at Highbury, Oxford Circus and Euston.

Unlike in some other places, I don't think the Victoria Line took over any existing running tunnels at Euston in order to have the cross-platform interchanges... there were changes to one of the Northern Line ones to enable a link to one of the Victoria line platforms, but the Vic running tunnels and platform tunnels were all newly built tracks.

 

[Ken H]

Unlike in some other places, I don't think the Victoria Line took over any existing running tunnels at Euston in order to have the cross-platform interchanges... there were changes to one of the Northern Line ones to enable a link to one of the Victoria line platforms, but the Vic running tunnels and platform tunnels were all newly built tracks.

Finsbury park reused old gt northern and city tunnels. Hibury used one GN&C tunnel and a new tunnel was driven to replace it. The northen line city branch was diverted at euston because the old station was a narrow island. The victoria line was squeezed between the 2 northern line tunnels to allow cross platform interchange. But you cross to the other platform and trains are running in the opposite direction! (Becausr the Victoria line is on a right-left dogleg and the northern city branch on a left-right dogleg)

 

[Tetchytyke]

there were changes to one of the Northern Line ones to enable a link to one of the Victoria line platforms, but the Vic running tunnels and platform tunnels were all newly built tracks.

The City branch had a narrow platform at Euston, so the northbound side was filled in, which is why the southbound platform is so wide. The southbound Victoria line platform was a new build next to it, and the northbound City branch and northbound Victoria platforms were new builds too.

But you cross to the other platform and trains are running in the opposite direction!

It's funny how they're paired southbound/southbound and vice versa but travelling in opposite directions.

 

[edwin_m]

Hibury used one GN&C tunnel and a new tunnel was driven to replace it.

Good thing that new tunnel was made to main line dimensions, otherwise it would have been much more difficult to transfer the line to the GN suburban services a few years later.

 

[AlbertBeale]

It's funny how they're paired southbound/southbound and vice versa but travelling in opposite directions.

Funny (and confusing for some people) - but sensible!

 

[Ken H]

Good thing that new tunnel was made to main line dimensions, otherwise it would have been much more difficult to transfer the line to the GN suburban services a few years later.

I think running trains from north of finsbury park was on the drawing board when they designed the new layout.