Cost of big and small tubes
 

I have been told that the cost of making new tube tunnels depends on their
size, with Crossrail-style NR-standard tunnels being more expensive than
classic LU-style tube tunnels. Is that true? If so, why, and how big is
the difference?

I can see why it might be greater - there's more mass to shift, more
surface to line - but not massively greater. If it's only a bit more
expensive, wouldn't it have made sense to build the underground to be
compatible with the rest of the network, as, AIUI, in Tokyo?

Thanks,
tom

--
forget everything from school -- you are programmer

Cost of big and small tubes
 

Tom Anderson writes:
I have been told that the cost of making new tube tunnels depends on
their size ...

Well, sure. There's more mass to shift, and more surface to line.

I can see why it might be greater - there's more mass to shift, more
surface to line ...

There, see? :-)

A further issue is that in some cases only a small tube may be able
to fit into a narrow vertical or horizontal space between existing
obstacles -- either older tunnels or other underground structures, or
geological strata that you really don't want to have to tunnel through.
A large tunnel, if possible at all, would then incur special costs due
to moving the existing structures or tunneling through the difficult
terrain.

but not massively greater.

Typically that's true. I don't have numbers.

If it's only a bit more expensive, wouldn't it have made sense to
build the underground to be compatible with the rest of the network...?

Only if you think it's sensible for through services to be able to
operate between them using main line rolling stock, or for main line
rolling stock to be usable on the Underground even in the absence of
through services.

Historically, the subsurface lines (District, Hammersmith & City,
Metropolitan, etc.) *were* considered as an extension of the main-line
railway network, were built for compatibility with it, and were served
by through trains using main-line rolling stock.

But later management saw the inter-working as a source of problems and
found it preferable to treat these lines as a separate sort of thing;
main-line connections at Ealing Broadway, Kensington (Olympia),
Paddington, King's Cross, St. Pancras, Farringdon, Liverpool Street,
Shoreditch, New Cross, New Cross Gate, and other points I can't
remember offhand were all taken out of regular service, and in most
cases the connecting tracks were eventually lifted.

The tube lines, on the other hand, are descended ultimately from the
Tower Subway of 1870, the little cable-operated line whose tunnel
diameter was only about 6'8". When you compare a tunnel *that* size
to a tunnel of 16' or more to carry main-line stock, the incremental
costs don't look so small!

The promoters of the Tower Subway planned their second line to be
slightly larger, using 8' tubes; after the Tower Subway failed, they
suspended the proposal, then eventually upgraded it to the longer and
larger line that opened in 1890 as the City & South London Railway,
using a tube diameter of 10'2". This was still viewed as a self-
contained line for local traffic, so there was no strong reason for
compatibility. In fact, it was going to be cable-hauled until late
in the construction period.

It was found that the C&SLR trains were inconveniently small; the
next few tubes, opened from 1898 to 1907, mostly chose slightly
larger diameters and this gave rise to today's standard, while the
the C&SLR was enlarged to a compatible tunnel size at considerable
cost and inconvenience. But it wasn't until the suburban extensions
of the 1930s that people really started thinking of tube train routes
of the length that now exist, and by then the small size was pretty
much locked in.
--
Mark Brader "You have seen this incident, based on
Toronto sworn testimony. Can you prove that it
didn't happen?" -- Plan 9 from Outer Space

My text in this article is in the public domain.

Cost of big and small tubes
 

Tom Anderson wrote:
I have been told that the cost of making new tube tunnels depends
on their size, with Crossrail-style NR-standard tunnels being more
expensive than classic LU-style tube tunnels. Is that true? If so,
why, and how big is the difference?

I can see why it might be greater - there's more mass to shift, more
surface to line - but not massively greater.

I think you may not have seen the actual figures. AFAIK these are
external tunnel dimensions (from Crossrail documents):
Victoria Line: 3.81m (older tube tunnels are slightly smaller)
Jubilee Line extension: 4.35m diameter
Crossrail: 6m diameter

Volume to excavate per metre of tunnel:
Victoria: 11.4m³ Jubilee: 14.9m³ Crossrail: 28.3m³
Surface area to line per metre of tunnel:
Victoria: 12.0m² Jubilee: 13.7m² Crossrail: 18.9m²

If it's only a bit more expensive, wouldn't it have made
sense to build the underground to be compatible with the
rest of the network, as, AIUI, in Tokyo?

London was the first city with deep-level tubes; the technology was in
its infancy, and a 12-foot diameter tunnel was probably as big as could
be managed at the time. Cost and the need for interconnections (e.g.
Victoria Line trains to Acton Works for major engineering work) were
factors which inhibited a subsequent change to mainline gauge.

--
Richard J.
(to e-mail me, swap uk and yon in address)

Cost of big and small tubes
 

Tom Anderson wrote:
I have been told that the cost of making new tube tunnels depends on
their size, with Crossrail-style NR-standard tunnels being more
expensive than classic LU-style tube tunnels. Is that true? If so,
why, and how big is the difference?

I can see why it might be greater - there's more mass to shift, more
surface to line - but not massively greater. If it's only a bit more
expensive, wouldn't it have made sense to build the underground to be
compatible with the rest of the network, as, AIUI, in Tokyo?

At the time the tube lines were envisaged I don't think there was any idea
of getting them anywhere near the main lines.

The sub-surface lines can accomodate main line gauge stock although it does
get a bit tight in places with modern stock. In 1982 a test run was carried
out with two battery locos and a BR Mk2 coach. It got round the Circle
although it did touch in a couple of places. This was in preparation for
passenger workings using ex-Met loco No12 Sarah Siddons. In the event these
workings were limited to the Met Main to Amersham and Uxbridge. Sorry can't
be certain where the southern reversal point was, but I think Wembley Park.

Until 1939 there was a through working between Ealing Broadway and Southend
using London Tilbury & Southend Railway rolling stock. Haulage from Ealing
to Barking was by electric loco and from there by LTS steam loco. Prior to
WW1 a number of main line companies provided services over the Metropolitan
and Metropolitan District Railways.

Cost of big and small tubes
 

Richard J.:
London was the first city with deep-level tubes; the technology was in
its infancy, and a 12-foot diameter tunnel was probably as big as could
be managed at the time...

I don't think there was any technical problem with a larger tunnel;
it just wasn't considered commercially necessary. Remember, the Great
Northern & City opened in 1904, just 14 years after the City & South
London, with 16' tubes intended for main line trains (which, in the
end, did not arrive until 1976).
--
Mark Brader "People with whole brains, however, dispute
Toronto this claim, and are generally more articulate
in expressing their views." -- Gary Larson

My text in this article is in the public domain.

Cost of big and small tubes
 

"Richard J." wrote in message
...
Tom Anderson wrote:

I can see why it might be greater - there's
more mass to shift, more
surface to line - but not massively greater.

I think that nowadays these seem to be a relatively small part of the cost
of building a railway.

I think you may not have seen the actual figures. AFAIK these are
external tunnel dimensions (from Crossrail documents):
Victoria Line: 3.81m (older tube tunnels are slightly smaller)
Jubilee Line extension: 4.35m diameter
Crossrail: 6m diameter

Volume to excavate per metre of tunnel:
Victoria: 11.4m³ Jubilee: 14.9m³ Crossrail: 28.3m³
Surface area to line per metre of tunnel:
Victoria: 12.0m² Jubilee: 13.7m² Crossrail: 18.9m²

Something else worth considering is that a crossover cavern has to have more
than twice the radius of the running tunnels, and four times the
cross-sectional area. For Crossrail in particular the crossover caverns
would be, well, cavernous, and the potential for surface disruption above
such a large void is significant. This is why there were going to be no
crossovers or sidings in the tunnel section at all, although apparently TPTB
have now changed their minds about this.

Another thing worth mentioning is that most of the UndergrounD was
deliberately built beneath public highways in order to avoid wayleave
payments to landowners. This meant putting the two tunnels on top of each
other in many places, especially around corners. The impact of tunnel size
should be obvious.

Further to one of Mark Brader's points, when Crossrail 2 (aka Chelsea
Hackney) was planned to be tube gauge it was planned to have a station at
Piccadilly Circus. When the plan changed to mainline gauge, this station was
deleted from the plan because there is not enough room in that area for the
larger platform tunnels that a mainline gauge line would need.

--
John Rowland - Spamtrapped
Transport Plans for the London Area, updated 2001
http://www.geocities.com/Athens/Acro...69/tpftla.html
A man's vehicle is a symbol of his manhood.
That's why my vehicle's the Piccadilly Line -
It's the size of a county and it comes every two and a half minutes

Cost of big and small tubes
 

John Rowland:
Something else worth considering is that a crossover cavern has to
have more than twice the radius of the running tunnels, and four times
the cross-sectional area.

Well, that's true if the crossover is placed in a cylindrical cavern
and the two through tracks are straight and, immediately beyond the
cavern, in separate single-track tunnels. If making a crossover cavern
that size is a major problem, other geometries are possible. For
example, trains of moderate speed can have tracks spaced close enough
to use a single twin-track tunnel smaller than twice the diameter of
a single-track tunnel, and crossovers can fit within this.

Another option is step-plate junctions at each end of the crossover.
Another option is non-cylindrical tunnels, with stronger lining as needed.

Another thing worth mentioning is that most of the UndergrounD was
deliberately built beneath public highways in order to avoid wayleave
payments to landowners.

Indeed, in the early days it wasn't even legal to tunnel under someone
else's private property; you had to buy it outright. My impression from
what I've read is that this changed between 1890 and about 1900, but
I don't know exactly when.
--
Mark Brader "Could you please continue the petty bickering?
Toronto I find it most intriguing."
-- Data ("Haven", ST:TNG, Tracy Torme)

My text in this article is in the public domain.

Cost of big and small tubes
 

Tom Anderson wrote:
wouldn't it have made sense to build the underground to be
compatible with the rest of the network, as, AIUI, in Tokyo?

Digressing a bit, I've always wondered why the South coast of England
(mainly the South East) uses the 700V DC "third rail" system for electrical
power, when the entire rest of the UK uses the 25000V AC overhead cable
system. Wouldn't it make more sense to have the same used all over the UK?
It means that a lot of national-running trains have to be diesel.

--
"We are now approaching Paisley Gilmour Street"

Cost of big and small tubes
 

One of the books about the tube (can't remember which) talks about the cost
of tunnelling being proportional to the square of the diameter of the bore.
This may concur with Richard J's figures below?



"Richard J." wrote in message
...
Tom Anderson wrote:
I have been told that the cost of making new tube tunnels depends
on their size, with Crossrail-style NR-standard tunnels being more
expensive than classic LU-style tube tunnels. Is that true? If so,
why, and how big is the difference?

I can see why it might be greater - there's more mass to shift, more
surface to line - but not massively greater.

I think you may not have seen the actual figures. AFAIK these are
external tunnel dimensions (from Crossrail documents):
Victoria Line: 3.81m (older tube tunnels are slightly smaller)
Jubilee Line extension: 4.35m diameter
Crossrail: 6m diameter

Volume to excavate per metre of tunnel:
Victoria: 11.4m³ Jubilee: 14.9m³ Crossrail: 28.3m³
Surface area to line per metre of tunnel:
Victoria: 12.0m² Jubilee: 13.7m² Crossrail: 18.9m²

Cost of big and small tubes
 

AyrAlex wrote:
Tom Anderson wrote:

wouldn't it have made sense to build the underground to be
compatible with the rest of the network, as, AIUI, in Tokyo?


Digressing a bit, I've always wondered why the South coast of England
(mainly the South East) uses the 700V DC "third rail" system for electrical
power, when the entire rest of the UK uses the 25000V AC overhead cable
system. Wouldn't it make more sense to have the same used all over the UK?
It means that a lot of national-running trains have to be diesel.

I know little of the history of the Southern Railway, but I believe that
it was decided to let the electrification, parts of which were done back
in the time of Yerkes, to proceed apace - IIRC this electrification
contributed to the sparse tube coverage in South London.

Besides, wasn't 25kVAC thought up well after 700V DC anyway?

Brad