sharky wrote:
Mizter T wrote:
Colin wrote:

Just reported on the news channels. 20m of the tunnel being built
above the
line at Gerrards Cross has collapsed moments after two trains
passed each
other within the tunnel.

Pictures show the collapse is huge. The line will undoubtedly be
blocked for
over a week at least.

Looks like it was extremely lucky that no-one was killed.


This website, by a uk.railway contributor, has some great photos of
the
tunnel collapse:

http://freespace.virgin.net/guy.gorton/collapse.html

Also see this thread:

http://groups.google.co.uk/group/uk....3fe6b98dac72c7
14/a64262cfd057e042#a64262cfd057e042


Looking at those pictures, the top of the tunnel seems to be very
flat,
even on the 'before' pictures.
I thought a tunnel/bridge needed to be arch shaped to support load
above - those seem to be two right angle bends with a flat section
across the
top - surely obviuosly not right.
Perhaps the sides were two wide apart, leaving and unnaturaly flat
meeting point?

Take a look at the Maidenhead bridge arches.