On Sep 10, 11:38*pm, wrote:
On Thu, 10 Sep 2009 17:33:10 +0100, Tom Barry
wrote:





wrote:
On Wed, 9 Sep 2009 16:06:03 +0100
"Basil Jet" wrote:
wrote:
*sigh* I hate to break this pre-GCSE news to you, but the area of the
shaft of a cylinder increases *linearly* with increasing radius, not
as the square of it so the cost of the lining will not go up like
that. The formula you want incidentaly is 2*pi*r*h. So before you
post anymore bull**** pretending your in-the-biz you might want to
revisit your school books first.
It's a good job you didn't write those schoolbooks, otherwise they'd say
that a one-inch diameter pipe and a five-metre diameter pipe need walls
which are the same thickness.

Remind me how a 10% increase in diameter size required to fit UIC gauge trains
in the tunnel in mostly self supporting london clay is going to cost so much
more because of huge extra lining thickness apparently required.

B2003

I hate to leap to the defence of either of you, but I suspect Bruce's
comment about the costs of *excavation* is more relevant than the costs
of lining. *The area of lining is proportionate to the radius of the
bore, but the weight of excavated material is proportionate to the
square of the radius, as are transport and disposal costs. *Add in the
strengthening required for the greater load borne by the lining for a
bit more £ on top, this obviously includes transport costs for whatever
they're using for the lining.

What's missing in this back-and-forth ranting is an estimation of the
proportion of Crossrail costs that are directly related to the
tunnelling rather than the station fit-out, land acquisition,
electrification, trains etc. *If it's only 5% of the costs, then going
large won't break that much of the bank. *If it's 50%, then you're
talking in £billions.

One other benefit of double-deck trains, by the way, is shorter train
lengths for the same capacity (which saves money on station lengths, but
not in the capacity of escalators etc.). That's at the expense of dwell
times, though, unless you do something really clever like having
double-height platforms with doors on the upper deck too (I like the
sound of that, actually).

Tom

Would there be sufficient space to build larger tunnels, or will they
be so deep as to avoid other tunnels, foundations etc. ?

Your specific question, I cannot answer. IIRC Crossrail will be
something of a roller coaster. It has to a avoid considerable
"stuff"
that is already along its route!