Bruce wrote:
On Wed, 18 Nov 2009 23:18:36 GMT, "Richard J."
wrote:
You're talking as though the problem is insufficient brickwork at the
top of the arch. But it's clear from the photo that the failure occurred
lower down, where a great mass of brickwork has moved. Looks like a
gross failure of the foundations.


Indeed it does. It is probably a result of scour under the
foundations as a result of the extreme flows of water.


I wonder why it was necessary to renew so much of the brickwork at the
top of the arch (different colour bricks obvious in photo). This is
pure speculation, but I'm wondering whether there was some earlier
instability of the foundations that resulted in some movement higher up,
which was just patched up rather than properly investigated.


More likely, a combination of gradual long term settlement of the
structure (it appears to be very old) and frost damage to the
brickwork. Problems can then be caused by using hard modern bricks
and hard cement mortar, rather than the hand made clay bricks and
slightly flexible lime mortar that would have been used in the
original structure.

I don't go with 'constant change' theory. More like a typical foundation
that has been undermined by a particular rainfall event. In the photo
you can see the head loss in the stream and associated turbulence with
eroding power. Once the foundations start to go, there is nothing to
hold up abutment, and then the arch fails.
Numbers of such brick culverts fail, often to be replaced by piled
foundations set further back, and concrete beams spanning the gap and
redundant footings. I remember a serious failure near Godalming, in
'68?, and i know of a place where it is possible to walk beneath a main
line on the footings of an old culvert, with concrete beams of a good
few metres now spanning a much larger gap.

Jim Chisholm