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Yooski

London Underground Tunnel Cross Section

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Hello,

 

I was wondering if anyone knows if there is a cross-sectional image of one of london undergrounds deep tunnel lines, with accurate measurements for the diameter of the tunnel, track bed height, rail height etc?

I have been pulling my hairout but all i have managed to fine so far is these but it is just a structure gauge and not the actual tunnel! argh!tunnel_dimensions_cast_iron_tunnel.jpg

 

Any help would be greatly appreciated!

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The tunnel diameter differs between lines/locations, according to exactly when each was built, and, on some lines, is greater on curves below a given radius, to allow for end and centre throw on the cars, but the "typical" diameter quoted, inside the flanges of cast iron segments, is 12ft. If you want chapter and verse on all the different figures, and which sections have concrete, as opposed to iron, linings, refer to "Rails Through The Clay" by Croome and Jackson, which is the standard history. The index gives 41 references to tunnel diameters, so you can see that there is no, one, simple answer to your question!

 

The Jubilee Line extension, which was at planning and design stage when my 1993 edition of RttC was published, is significantly larger diameter (4.35m), because it incorporates space for a side walkway.

 

You'll find this interesting http://www.nycsubway.org/wiki/Oldest_London_Tube_Reopened_(City_&_South_London)_(1925)

 

Kevin

 

PS: if you want to really get into this, most of the openings of lines have been accompanied by seriously deep articles, with plenty of diagrams, in the technical press: Engineering; The Engineer; Journal of ICE etc.

Edited by Nearholmer
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In a tunnel, all dimensions need to be taken from the centreline of the tunnel. There is no track bed height, only distance below the centreline.

 

The interior diameter is shown, you have to add 2 figures together to get it. The flange depth on the tunnel segments is not given, but you could calculate it from the drawing. The drawing appears to show cast iron segments, but in new tunnels, the segments are preformed concrete.

 

You could also work out the track bed "height" by using the drawing, which look like the one on the Metromodels website.

 

Whilst you should not scale from a drawing, the original will have been accurately drawn by a draughtsman or engineer from the actual dimensions. But for modelling purposes, scaling from the drawing will be accurate enough.

 

If you are modelling a tunnel segment, just buy 2"/50mm rainwater down pipe. It is equivalent to a 12ft 6in internal diameter, and lay your track in that. It will be slightly too "high", but your tube rolling stock will fit if you're using standard OO Peco track. You could shorten the sleepers to drop it down a bit.

 

I'm currently building a card kit of a tube station, and have been juggling these dimensions myself to get everything to fit.

 

Going back to Nearholmer's point about tunnel diameter, it is even more complicated than when it was built. The Central Line tunnels between Shepherds Bush and Bank were enlarged in the 1930s to take Standard stock and make space for the 4th outer conductor rail. This was done, IIRC, by inserting an extra segment. Hence the rebuilt tunnel is no longer its circular as built cross-section in the late 1890s/early 1900s

Edited by GoingUnderground
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3850mm diameter cast iron segments were commonly used for many years, some older lines used 3630mm although these are sometimes locally "eased" by taking out the key and top segments, excavating outside the ring and rebuilding using two extra keys. This gives extra clearance at the 10-11 o'clock and 1-2 o'clock positions, which tends to be the critical clearance between the dynamic envelope of the train, and the ring.

 

Some of the old C&SLR running tunnels at London Bridge (now incorporated into the piston relief and ventilation ducts at the Jubilee Line/Northern Line station) are 3350mm but I don't believe any survive in traffic anywhere on the network.

 

Bolted concrete rings look similar to the cast iron ones. The wedgeblock rings used in some areas present a smooth internal face. Some modern linings have track beds, or partial invert infills cast into them.

 

As a rule of thumb, sufficient for modelling, cast iron rings are 5" deep, bolted concrete 6-8" depending on supplier.

Edited by rockershovel
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Additionally, you might want to have a look at "Building London's Underground" by Antony Badsey-Ellis. Published by Capital transport ISBN 9-781854-143976 which was published Jan 2016 and is packed full of useful pics and information on both bored tunnel and cut & cover works and infrastructure.

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The City & South London tunnels were built to an internal diameter of 10ft 2in (3,099mm) diameter, (3,350mm external diameter) and later sections to 10ft 6in (3,200mm), for the "padded cell" rolling stock and Mather & Platt locos. But this became a problem when the original rolling stock needed to be replaced. So the entire route was enlarged in the 1920s so that it could use rolling stock of the same dimensions as the Yerkes Tube lines. Enlargement was achieved by incorporating extra segments. So the cross section will not be circular. The only remaining sections of C&SLR running tunnels at the original diameter will be those between Borough and the disused King William St station, which were bypassed when the line was extended to Moorgate in 1900.

Edited by GoingUnderground
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The King William Street Tunnels are the very ones that Rocker was referring to.

 

Has anyone built a model of the Post Office tube, I wonder?

 

K

No one has built a model of the Post Office Railway AFAIK but a few years ago there was a 00 scale diecast replica of one of the trains produced for a special event, I've only ever seen a picture of one.

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The King William Street Tunnels are the very ones that Rocker was referring to.

 

K

I wasn't disagreeing with him, just explaining where they were and when and why they were originally abandoned.

 

There was also a ramp tunnel used to cable haul rolling stock to the surface at Stockwell. That was replaced by a lift. I don't know what happened to that tunnel after it was abandoned, nor to the rolling stock lift shaft and presumably its connections to the running tunnels after the C&SLR was phsically connected to the Charing Cross, Euston & Hampstead lines and Stockwell depot closed.

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Straining the memory of working on the London Bridge JLE site at a distance now, of over twenty years, my recollection is as follows..

 

1) the abandoned CS&L running tunnels connected into a step plate in the West running tunnel of the existing Northern Line, North of Borough station and rise up above the existing tunnels in a sharply curved alignment (curved vertically and horizontally).

 

2) the CS&L running tunnels were used for compensation grouting and other temporary works during JLE operations around London Bridge station

 

3) the CS&L tunnels were subsequently incorporated into the piston relief and ventilation system at London Bridge and can be glimpsed from the platforms.

 

4) the CS&L tunnels continue to King William Street, but are not accessible North of London Bridge station, being bricked up there. The condition of the Thames crossing is unknown but can be inferred to be intact from the condition of the visible sections and lack of signs of water at the headwalls S of the river.

 

5) the new Northern Line alignment connected to the previous alignment at a step plate S of London Bridge

 

6) the new Northern Line alignment connected to the existing alignment at a direct junction N of London Bridge, and a closure took place for several weeks while this was effected.

 

7) there is, or was a flight of steps off the Northern Line running tunnel S of London Bridge (by the crossover) which leads to a high-level cross-tunnel connecting to the CS&L tunnels

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The City & South London tunnels were built to an internal diameter of 10ft 2in (3,099mm) diameter, (3,350mm external diameter) and later sections to 10ft 6in (3,200mm), for the "padded cell" rolling stock and Mather & Platt locos. But this became a problem when the original rolling stock needed to be replaced. So the entire route was enlarged in the 1920s so that it could use rolling stock of the same dimensions as the Yerkes Tube lines. Enlargement was achieved by incorporating extra segments. So the cross section will not be circular. The only remaining sections of C&SLR running tunnels at the original diameter will be those between Borough and the disused King William St station, which were bypassed when the line was extended to Moorgate in 1900.

Strictly speaking the expanded rings employ extra keys, not extra segments

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The additional segments may be the same shape and dimensions as a "key", but they would not form the same engineering purpose, as the key locks the structure in place. In the enlargement they simply expand the tunnel. There is still the need for the original key at the apex of the tunnel.

 

Looking at the Video 125 "Northern Line Driver's Eye View" video, the original tunnel segments appear to be 60 degree ones, i.e. 6 to a complete ring, plus the Key at the apex. The additional "enlarging keys" have been inserted at 60, 120, 240 and 300 degrees, taking the apex as 0 degrees. The true key can be seen at the apex of the tunnel. The use of 60 degree segments is another difference from the drawing that started this thread, where 45 degree segments are shown, i.e. 8 to a complete ring, plus a Key at the apex.http://www.metromodels.net/tunnel_dimensions_cast_iron_tunnel.jpg

 

 

The Yerkes tube lines appear to have standardised on 11ft 8 1/4 in internal diameter, 6 segment rings for running tunnels, and 21ft 2 1/4 in internal diameter for station tunnels. 

Edited by GoingUnderground
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Stockwell .......

 

There are lots of photos taken in and around the works and generating station, in the LTM collection.

 

Map below shows the site, which I think was eradicated and built over with a block of flats in the 1920s. My interpretation (or guess!) is that the slope shaft is the building towards the lower LHS, entered by a single track.

 

The photo shows, I think, a loco on the spur into the larger building at upper LHS, which I think is the generating station.

 

One of my ex-colleagues is PIC the engineering records at LU, but I think that all the material about this site has gone to LTM already.

 

Anyone have the book on the history of the CSLR/Northern, possibly by Piers Connor or Mike Horne? That will have more details, I think.

 

Kevin

post-26817-0-50010600-1495030488_thumb.jpg

post-26817-0-98345600-1495030499_thumb.jpg

Edited by Nearholmer
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The additional segments may be the same shape and dimensions as a "key", but they would not form the same engineering purpose, as the key locks the structure in place. In the enlargement they simply expand the tunnel. There is still the need for the original key at the apex of the tunnel.

 

Looking at the Video 125 "Northern Line Driver's Eye View" video, the original tunnel segments appear to be 60 degree ones, i.e. 6 to a complete ring, plus the Key at the apex. The additional "enlarging keys" have been inserted at 60, 120, 240 and 300 degrees, taking the apex as 0 degrees. The true key can be seen at the apex of the tunnel. The use of 60 degree segments is another difference from the drawing that started this thread, where 45 degree segments are shown, i.e. 8 to a complete ring, plus a Key at the apex.http://www.metromodels.net/tunnel_dimensions_cast_iron_tunnel.jpg

 

 

The Yerkes tube lines appear to have standardised on 11ft 8 1/4 in internal diameter, 6 segment rings for running tunnels, and 21ft 2 1/4 in internal diameter for station tunnels.

 

That's not quite correct. The rings shown have a single key at the crown. You are misinterpreting the drawing, which is a general arrangement showing the ring proper plus various hangers and fittings within the finished tunnel

 

Broadly speaking, cast iron tunnel rings and the bolted concrete rings which largely (though by no means entirely) succeeded them consist of a number of segments which varies with the diameter. The segments are of a size which can be transported through the tunnel and handled into place, usually within the tail of the Tunnelling shield.

 

The bolts joining successive rings (circle bolts) are distributed around an equal pitch circle. The ring is constructed by placing the invert plate or plates (sometimes "rocker plates") then placing successive plates and inserting the circle and seat bolts and erection progresses. These plates are symmetrical about the pitch circle and are known as "Ordinary" or simply "O" plates. They are sometimes marked with a cast-in O

 

The two top plates, known as "Top" or "T" plates, are shorter at one end. This is because it is not possible to pass a full length plate into position - the external circumference being longer than the internal. Hence the T plates are shorter about the bolt circle at one end, often marked with a cast T symbol. Once the T plates are in temporary position, they are spread slightly and the key inserted, then longer seat bolts (or "key bolts") inserted. The whole circle is then closed and bolts tightened.

 

The shield is shoved forwards and the annular gap, filled with a cement/PFA grout.

 

Keys are usually, though not invariably, alternated centre-right-centre-left-centre on consecutive rings to avoid continuous longitudinal joints, which assists with the strength and alignment of the finished tunnel. However joints may be consecutive in certain cases e.g. To accommodate side connections, or to assist correcting accumulated distortions in circularity.

 

When expanding rings, it is quite feasible to substitute two O plates for two T plates and a key, since two Os add up to two Ts and a key, but this is not normally done as it serves no useful purpose

 

Rings larger than 3850mm diameter may have two keys, either at the shoulder or knee, typically associated with mechanical erection.

 

There is another, quite different type of ring, known as a "wedgeblock" and used since the 1960s. The wedgeblock ring is of unreinforced concrete construction, with no seat or circle bolts. It was used in good firm clay, behind a tailless shield. The segments are placed directly on the cut clay, and the final key section is tapered longitudinally, with Top plates tapered accordingly. The key is inserted from a pocket in the shield, by a ram which shoves it home and thereby stresses the ring against the cut, locking it in place. No grouting is carried out, or required, although there will be a gap at the leading edge of the key which requires pointing.

 

Wedgeblock keys are consecutive because they must match the key ram in the shield

 

Larger types may have two keys, typically at the knees. By leaving the keys forward, space is provided to insert the uppers and close the circle, then the keys are shoved home and the ring locked.

 

Wedgeblock rings are an obsolete type now, modern tunnels are constructed either using hybrid designs combining bolted and stressed-key construction, or sprayed concrete techniques (broadly referred to as NATM although NATM proper, is simply one such technique)

Edited by rockershovel
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Stockwell .......

 

There are lots of photos taken in and around the works and generating station, in the LTM collection.

 

Map below shows the site, which I think was eradicated and built over with a block of flats in the 1920s. My interpretation (or guess!) is that the slope shaft is the building towards the lower LHS, entered by a single track.

 

The photo shows, I think, a loco on the spur into the larger building at upper LHS, which I think is the generating station.

 

One of my ex-colleagues is PIC the engineering records at LU, but I think that all the material about this site has gone to LTM already.

 

Anyone have the book on the history of the CSLR/Northern, possibly by Piers Connor or Mike Horne? That will have more details, I think.

 

Kevin

 

Kevin,

 

Thank you for the picture and the plan. I hadn't seen them before.

 

I've got Horne & Bayman's book. It refers to the depot at Stockwell becoming the principal worksite during the enlargement and says that it was then closed after the work completed, the power station having been shut down by UERL in 1915 and the C&SLR then taking its power from Lots Road. It adds that the site was sold off for housing development, but doesn't say whether the ramp tunnel and lift shaft were filled in or just capped.

 

That's not quite correct. The rings shown have a single key at the crown. You are misinterpreting the drawing, which is a general arrangement showing the ring proper plus various hangers and fittings within the finished tunnel

 

Broadly speaking, cast iron tunnel rings and the bolted concrete rings which largely (though by no means entirely) succeeded them consist of a number of segments which varies with the diameter. The segments are of a size which can be transported through the tunnel and handled into place, usually within the tail of the Tunnelling shield.

 

The bolts joining successive rings (circle bolts) are distributed around an equal pitch circle. The ring is constructed by placing the invert plate or plates (sometimes "rocker plates") then placing successive plates and inserting the circle and seat bolts and erection progresses. These plates are symmetrical about the pitch circle and are known as "Ordinary" or simply "O" plates. They are sometimes marked with a cast-in O

 

The two top plates, known as "Top" or "T" plates, are shorter at one end. This is because it is not possible to pass a full length plate into position - the external circumference being longer than the internal. Hence the T plates are shorter about the bolt circle at one end, often marked with a cast T symbol. Once the T plates are in temporary position, they are spread slightly and the key inserted, then longer seat bolts (or "key bolts") inserted. The whole circle is then closed and bolts tightened.

 

The shield is shoved forwards and the annular gap, filled with a cement/PFA grout.

 

Keys are usually, though not invariably, alternated centre-right-centre-left-centre on consecutive rings to avoid continuous longitudinal joints, which assists with the strength and alignment of the finished tunnel. However joints may be consecutive in certain cases e.g. To accommodate side connections, or to assist correcting accumulated distortions in circularity.

 

When expanding rings, it is quite feasible to substitute two O plates for two T plates and a key, since two Os add up to two Ts and a key, but this is not normally done as it serves no useful purpose

 

Rings larger than 3850mm diameter may have two keys, either at the shoulder or knee, typically associated with mechanical erection.

 

There is another, quite different type of ring, known as a "wedgeblock" and used since the 1960s. The wedgeblock ring is of unreinforced concrete construction, with no seat or circle bolts. It was used in good firm clay, behind a tailless shield. The segments are placed directly on the cut clay, and the final key section is tapered longitudinally, with Top plates tapered accordingly. The key is inserted from a pocket in the shield, by a ram which shoves it home and thereby stresses the ring against the cut, locking it in place. No grouting is carried out, or required, although there will be a gap at the leading edge of the key which requires pointing.

 

Wedgeblock keys are consecutive because they must match the key ram in the shield

 

Larger types may have two keys, typically at the knees. By leaving the keys forward, space is provided to insert the uppers and close the circle, then the keys are shoved home and the ring locked.

 

Wedgeblock rings are an obsolete type now, modern tunnels are constructed either using hybrid designs combining bolted and stressed-key construction, or sprayed concrete techniques (broadly referred to as NATM although NATM proper, is simply one such technique)

Clearly, you are, or have been, in the construction business whereas my last contact with it was over 40 years ago.

 

No, I am not misinterpreting the drawing, and am aware that the T segments would need to be shorter than the O segments to get them in place, and that the key then fills the resulting gap.

 

The "Northern Line Illustrated History" mentioned by Nearholmer states that rings had been enlarged, "... in many instances by re-using existing segments with additional key pieces inserted within each tunnel ring.". That would be consistent with the aim of keeping the line open and minimising the cost. But these new key pieces would seem to have been fitted between existing O segments, not T segments, at what I think you called the "knee" and "shoulder" positions on both sides of the ring. so that the existing T segments and key could themselves be reused. Or at least that is how i am interpreting the tunnel appearance in the the video.

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That's correct. I worked for J Murphy and Sons, mostly on tunnel construction around Central London, for several years during the 1980s-90s oil price collapse. I've worked on this sort of clearance work.

 

Typically, the pinch points are at the upper corners of the dynamic envelope, or at the crown.

 

The procedure is to bring in a work train which provides a working platform. The key is unbolted and loosened using air picks, and lowered onto the train. The two T plates are then removed, and a shim of clay and/or grout is trimmed using air spades. The additional keys are inserted on the seat joints, using new longer bolts and the original plates and key replaced. The rebuilt ring is then grouted. The cycle is carried out on overnight PI sessions.

 

It's not usual for complete rings to be rebuilt, that needs a closure. There WAS a closure of that sort in 1999 or so, the very tight curves between Moorgate and Bank were eased in that fashion, but it's rare

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That's correct. I worked for J Murphy and Sons, mostly on tunnel construction around Central London, for several years during the 1980s-90s oil price collapse. I've worked on this sort of clearance work.

 

Typically, the pinch points are at the upper corners of the dynamic envelope, or at the crown.

 

The procedure is to bring in a work train which provides a working platform. The key is unbolted and loosened using air picks, and lowered onto the train. The two T plates are then removed, and a shim of clay and/or grout is trimmed using air spades. The additional keys are inserted on the seat joints, using new longer bolts and the original plates and key replaced. The rebuilt ring is then grouted. The cycle is carried out on overnight PI sessions.

 

It's not usual for complete rings to be rebuilt, that needs a closure. There WAS a closure of that sort in 1999 or so, the very tight curves between Moorgate and Bank were eased in that fashion, but it's rare

In the case of the C&SLR it was more than just easing pinch points. It was a major enlargement by 18 inches from 10ft 2in to 11ft 8in.which seems to have dictated the removal of not just the T segments and the key, but also the O segments adjoining the T segments, which is what I believe this still shows.

 

post-6983-0-21661100-1495059325_thumb.jpg

 

I think the two extra  keys are clearly shown, particularly on the right hand tunnel wall, as that would have given the necessary vertical enlargement. But that woudl still leave the width at much less than 11ft 8in. So they may also have replaced the apex key with a wider one to give added clearance at the upper corners as well.

 

So back to the OP. I think this debate just proves that there is no absolute design standard on LU. The most often used diameter is 11ft 8 1/4 in internal diameter, which is quoted in various reference books as having been used on the original Yerkes Tube lines and also the CLR. Judging frm various "Driver's Eye View" videos, there would have been 6 segments to a ring. What I haven't found, yet, is the width of a ring, but I from looking at various pictures they appear to be somewhere between 2 and 3 feet wide. 

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Oh ok, I'd forgotten about those. Those are panel type keys, an earlier design which still sometimes appears on larger diameters to reduce the weight of the key (on smaller sizes it is usually a solid block).

 

There is certainly no standard design of ring for the older, deep tubes. Later ones use LUL design standard cast iron rings in 3850mm, 5750mm and 7500mm diameters (7500 is a common size for escalator shafts). There were various odd shapes for passenger ways (the individual escalators at Liverpool St were a sort of coffin shape, which I've never seen anywhere else).

 

Later rings are usually 610mm = 24" long, but earlier ones are often 16" or 18". The early shields had shorter rams, and the piece weight of the ring segments had to be controlled to allow manual handling and erection. Later bolted concrete rings were 24". Modern rings are typically 1m, because modern machinery can handle larger pieces (there is also a functional relationship between the length of the ring, the diameter of the ring and the practicalities of steering the shield)

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  • RMweb Gold

I think there are some tunnel ring samples, even a complete ring, at the Acton depot museum.

I have a book with some drawings of the Greenwich foot tunnel design, stated to be similar in size to one of the the early tube lines. I can scan and post if interesting.

 

Thanks

 

Dave

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Oh ok, I'd forgotten about those. Those are panel type keys, an earlier design which still sometimes appears on larger diameters to reduce the weight of the key (on smaller sizes it is usually a solid block).

 

There is certainly no standard design of ring for the older, deep tubes. Later ones use LUL design standard cast iron rings in 3850mm, 5750mm and 7500mm diameters (7500 is a common size for escalator shafts). There were various odd shapes for passenger ways (the individual escalators at Liverpool St were a sort of coffin shape, which I've never seen anywhere else).

 

Later rings are usually 610mm = 24" long, but earlier ones are often 16" or 18". The early shields had shorter rams, and the piece weight of the ring segments had to be controlled to allow manual handling and erection. Later bolted concrete rings were 24". Modern rings are typically 1m, because modern machinery can handle larger pieces (there is also a functional relationship between the length of the ring, the diameter of the ring and the practicalities of steering the shield)

Thank you for the information about the width of the rings. Just shows how difficult it can be to judge dimensions by eye from a less than perfect viewpoint. A ring width of 18in sounds like a good basis to use if trying to model running tunnel on a tube line.

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I think there are some tunnel ring samples, even a complete ring, at the Acton depot museum.

I have a book with some drawings of the Greenwich foot tunnel design, stated to be similar in size to one of the the early tube lines. I can scan and post if interesting.

 

Thanks

 

Dave

Indeed there is a tube section at Acton Town. I'm not certain but I think it came from the Central Line.

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  • RMweb Gold

By co-incidence I've been archiving some society papers including plans of the GN & City Railway, it has some plans and cross sections of culverts and lift shafts but sadly not tunnels. 

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