From Newsgroup: uk.rec.waterways
On Tue, 23 Dec 2025 10:05:41 +0000
John Williamson <
johnwilliamson@btinternet.com> wrote:
On 23/12/2025 09:43, JMB99 wrote:
On 23/12/2025 08:25, Martin Nicholas wrote:
I was tied up right over the top of it during the summer! There is
a culvert under the canal right at that point - blown culvert
would be my guess as to the cause. It's not a sinkhole.
I think BBC News corrected themselves later and said something
about it being unlikely to be a sinkhole. They had probably
earlier been just repeating what someone had told them.
Some people seem a bit obsessed with sinkholes!
If you look at what causes a sinkhole, it is usually flowing water
escaping from a pipe washing soil away, which causes the surface soil
to sink into the hole.
If you have a culvert (A large pipe) under a canal which fails, that
washes soil away from its surroundings, which then causes the canal
bed to sink into the hole.
See the Bridgewater and Macclesfield breaches earlier this year, both
of which were caused by the failure of a culvert.
If it waddles and quacks, I call it a duck...
Not really saying any of these were caused by this, but another failure
mode of a culvert is when a blockage or an undersized (for the
conditions) culvert causes water pressure to build from below. Brick
arch culverts, like all arched structures, rely on pressure from above
to remain intact. So the culvert can collapse as a result or an
upwelling can breach the puddle; now you have a hole. I believe the
culvert failure at Streethay in 202? happened in that way. Also
the Bridgewater breach.
All the culverts on the Ll were built at roughly the same time using the
same methods, so I would think there will be one or two failures per
year for the foreseeable future. BW/CART need to devise a method of
fixing these using waterborne equipment. The stoppage between Chester
and Ellesmere Port was delayed by 40-days by site access problems.
There are two towpaths and two canals (once refilled) providing access
to any site.
Wikipedia on sinkholes:
https://w.wiki/HBV4
--
Regards,
Martin Nicholas.
E-mail:
reply-202512@mgn.org.uk (Address will be valid throughout
December).
Season's greetings to all our readers!
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