Tube Tunnel @ MLE

[Christopher J]

Gents,

I am aware that between Stepney Green and Mile End a part of the double tracked tunnel splits into two SLL size tube tunnels then reforms into doubled tracked tunnel again on the approach to Mile End EB.

Can anybody explain why this unique combination of tunnels is used at this particular location and why?

Answers appreciated.

Christopher

[Deleted]

A very good question! ;D

I'm sure one of our experts will know, but I suspect it is something to do with the pumping station which is attached to the east of those sections of tunnel.

[q8]

Well I'll tell you the answer then !! The tunnel is split at that point as it passes directly under a canal and in between the two tracks is a pump house as AlanL has said.. In my time the pump man used to go down there 2 or 3 times a week and be dropped of on the little platform at the Mile End side.

When he was finished he would flag down a following train with a red lamp.

Although it does not show up very well the canal can be seen as light blue here

EDIT : It is also the reason for the 'dip' at that point. The District is directly under the road all the way from Bow to Whitechapel and there is also a large sewer above the tunnel. Remind me to tell you sometime about the morning the sewer burst.

[trainopd78]

If you blow the map up to the next level, the canal is easily viewed. It's part of the regents canal that we go under at this point.

[q8]

Thank you Colin. I could not remember the name of the canal for the life of me. Although Bow Locks came to mind.

[Deleted]

It's also confirmed things for me too! Thanks lads! (BTW Bob, TrainOpD78 isn't Colin! ;D)

[stanmorek]

The section that you are referring to is CW34, which is the only part of the SSL network that is constructed from SGIs (Spheroidal Graphite Iron rings – the bolted tunnel sections).

CW34 is actually constructed under the Grand Union Canal/ Regent’s Canal. In order for the cut and cover method to be used, the canal would have to be closed and emptied for the duration of the works. Don’t forget that at this time London’s docks were very busy and there was still quite a lot of traffic being taken by canal. It would therefore have been very expensive and hugely impractical to close the canal so that the underground railway could be constructed. Thus a different from of construction was required. Here they would have bored through the ground (probably by hand), installing the SGIs as they went so that the ground behind the workers was supported. Obviously it would be much more difficult to construct a large bore twin track tunnel, therefore two single track tunnels were constructed.

[q8]

(BTW Bob, TrainOpD78 isn't Colin! ;D)
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OH!! I'm a daft beggar. I humbly ajollapise to the mis-nomered gentlemen.. (Kowtows, Grovels, whines, creeps , crawls)

[q8]

which is the only part of the SSL network that is constructed from SGIs (Spheroidal Graphite Iron rings – the bolted tunnel sections).

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Bit of a misnomer there methinks. Since when has a ring been 'Spheroidal'

'Circumfrital' yes 'Sphreoidal' no.

[Deleted]

christopherjolly said:

I am aware that between Stepney Green and Mile End a part of the double tracked tunnel splits into two SLL size tube tunnels then reforms into doubled tracked tunnel again on the approach to Mile End EB.

How can you have an SSL sized tube tunnel? The appropriate name would be single track tunnel.

There is a pump switch room along there, it has been mentioned before, to stop at it, trip everything out and then carry on to see what happens! You would have to do it on the right trip though, as you wouldnt want to be stuck the wrong side of it! ;D

[Tom]

It doesn't have to be 12ft diameter to be a tube - just constructed with iron rings like a tube. After all the GN&CR was 'The Big Tube' as it was signle track tubular tunnels but built for main line loading gauge.

[Deleted]

And even then the GN&CR was too small for energised 25kV AC (but not unenergised 25kV AC).

[trainopd78]

q8 said:

(BTW Bob, TrainOpD78 isn't Colin! ;D)
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OH!! I'm a daft beggar. I humbly ajollapise to the mis-nomered gentlemen.. (Kowtows, Grovels, whines, creeps , crawls)

Not to worry. It's much nicer than the names that I usually get called! ;D

[stanmorek]

q8 said:

which is the only part of the SSL network that is constructed from SGIs (Spheroidal Graphite Iron rings – the bolted tunnel sections).

-----------------------------------------------------------------------

Bit of a misnomer there methinks. Since when has a ring been 'Spheroidal'

'Circumfrital' yes 'Sphreoidal' no.

Circumferential yes but still made up of bolted segments. The spheroidal bit refers to the microstructure of the cast iron.

[q8]

Circumferential yes but still made up of bolted segments. The spheroidal bit refers to the microstructure of the cast iron.
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What a lovely bit of mediaspeak. ;D You're in the wrong proffession my freind. ;D

[Colin]

trainopd78 said:

q8 said:

(BTW Bob, TrainOpD78 isn't Colin! ;D)
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OH!! I'm a daft beggar. I humbly ajollapise to the mis-nomered gentlemen.. (Kowtows, Grovels, whines, creeps , crawls)

Not to worry. It's much nicer than the names that I usually get called! ;D

;D ;D ;D ;D ;D ;D ;D

[yellowsignal]

stanmorek said:

Circumferential yes but still made up of bolted segments. The spheroidal bit refers to the microstructure of the cast iron.

is that the same as nodular cast iron?

[russe]

yellowsignal said:

is that the same as nodular cast iron?

Yes I think so.

Russ