Merthyr Tydfil Sink Hole

[jonnybellman]

Sinkhole Merthyr Tydfil: Homes evacuated on Pant estate

About 30 homes are believed to have been evacuated and people were told to avoid the area.

www.bbc.com

Have we got ourselves a new cave?

 

[alanw]

It's a collapsed culvert.

Side by side georeferenced maps viewer - Map images - National Library of Scotland

The street has the same name: "Nant Morlais" as a stream which disappears on the 25k map of 1937-61. It can be seen continuing on the 6" map of 1888-1915

 

[shotlighter]

Sinkhole Merthyr Tydfil: Homes evacuated on Pant estate

About 30 homes are believed to have been evacuated and people were told to avoid the area.

www.bbc.com

Have we got ourselves a new cave?

Pit shaft? Crown hole?

 

[Huge]

Watch: Wall falls into sinkhole as man interviewed

 

[mikem]

The original report says it's a collapsed culvert (you can still see the stream further up on Google satellite images)

 

[Huge]

Watch: Wall falls into sinkhole as man interviewed

I like the insightful information given by the second guy being interviewed.

"It's a big hole, a big, big hole."
"A black hole."
"That's what it looks like, a big black hole."
Said Mr Bleeding Obvious, of Pant, Merthyr Tydfil!

 

[Martin Laverty]

An interesting two part account contributed by a Merthyr historian, including a picture of Pwll Morlais, an old karstic sink which had its water supply cut off long ago by a diversion to supply to the iron works below. The council now want to reduce the flow now culverted under much of Methyr - dare they consider reactivating this sink?
The Morlais Brook - Part 1
Part 2 starts at Cae Racca: this is where the ongoing 'sinkhole' collapse down to the culverted stream is
The Morlais Brook - part 2

 

[Rhys]

UKCaving member quoted by the BBC https://www.bbc.co.uk/news/articles/c93gpn4z95yo

"Andrew Farrant, a BGS geologist, said the sinkhole likely resulted from a collapsed culvert and recent heavy rainfall, rather than a natural geological cause and it was "not just a case of filling the hole".

He explained that repairs would involve stabilizing the void, excavating the site and reinstating the culvert to ensure the stream can flow safely."

 

[Huge]

An interesting two part account contributed by a Merthyr historian, including a picture of Pwll Morlais, an old karstic sink which had its water supply cut off long ago by a diversion to supply to the iron works below. The council now want to reduce the flow now culverted under much of Methyr - dare they consider reactivating this sink?
The Morlais Brook - Part 1
Part 2 starts at Cae Racca: this is where the ongoing 'sinkhole' collapse down to the culverted stream is
The Morlais Brook - part 2

A frozen Pwll Morlais back in January. It dries out completely in summer.

 

[martinr]

Guardian feature: Sinkholes around the world – in pictures

After a sizeable sinkhole appeared on a sleepy street in south Wales, here are some of the more incredible views of the phenomenon from Greenwich to Guatemala

https://www.theguardian.com/world/g...world-from-greenwich-to-guatemala-in-pictures

 

[Andy Farrant]

Guardian feature: Sinkholes around the world – in pictures

After a sizeable sinkhole appeared on a sleepy street in south Wales, here are some of the more incredible views of the phenomenon from Greenwich to Guatemala

https://www.theguardian.com/world/g...world-from-greenwich-to-guatemala-in-pictures

It is interesting to note that nearly all those sinkholes in the Guardian article are not natural karstic features, but mostly collapses over infrastructure (sewers, culverts), old mines or tunnels, the Merthyr collapse being one example. Only the Turkish ones are true karstic sinkholes, in that case on gypsum. The Guatemala sinkholes are due to soil piping in unconsolidated volcanic deposits from leaking sewer pipes.

 

[Lankyman]

The Guatemala sinkholes are due to soil piping in unconsolidated volcanic deposits from leaking sewer pipes.

According to the Guardian text, one of those holes is 150m deep! That's absolutely terrifying. To a non-geologist that sounds like more than leaking sewer pipes? Or is the report just inaccurate journalistic guff? I must admit the Guatemala City pictures look like the holes are impressively deep and sheer sided.

 

[Andy Farrant]

According to the Guardian text, one of those holes is 150m deep! That's absolutely terrifying. To a non-geologist that sounds like more than leaking sewer pipes? Or is the report just inaccurate journalistic guff? I must admit the Guatemala City pictures look like the holes are impressively deep and sheer sided.

Not inaccurate journalistic guff! See Waltham, T., 2008. Sinkhole hazard case histories in karst terrains. Quarterly Journal of Engineering Geology and Hydrogeology, 41(3), pp.291-300.

"The void that the Guatemala sinkhole collapsed into was created by soil piping, whereby seepage water had washed the fines out of the poorly consolidated sediment, progressively taking coarser material and eventually creating an open pipe that developed headwards towards its water input (a leaking sewer). Eventual failure of the undermined roof was an inevitable continuation of the piping process. No rock dissolution was involved, and it is therefore a pseudokarst feature. Comparable large piping failures and sinkhole collapses are well known in the loess lands of China."

 

[Lankyman]

Not inaccurate journalistic guff! See Waltham, T., 2008. Sinkhole hazard case histories in karst terrains. Quarterly Journal of Engineering Geology and Hydrogeology, 41(3), pp.291-300.

"The void that the Guatemala sinkhole collapsed into was created by soil piping, whereby seepage water had washed the fines out of the poorly consolidated sediment, progressively taking coarser material and eventually creating an open pipe that developed headwards towards its water input (a leaking sewer). Eventual failure of the undermined roof was an inevitable continuation of the piping process. No rock dissolution was involved, and it is therefore a pseudokarst feature. Comparable large piping failures and sinkhole collapses are well known in the loess lands of China."

Thanks. Does anyone know what's down below (or even gone to have a look)? And how the hell do you deal with a 150m deep hole opening up in a city? Seems like a bit of concrete and rubble won't do it.

 

[Andy Farrant]

Thanks. Does anyone know what's down below (or even gone to have a look)? And how the hell do you deal with a 150m deep hole opening up in a city? Seems like a bit of concrete and rubble won't do it.

I would be extremely wary of investigating any passages (assuming they were accessible) at the bottom of a deep shaft in unconsolidated weak sediment, especially one created by sediment being washed out by effluent from a leaking sewer... Imagine!! I suspect it got infilled pretty quick with anything the locals could lay their hands on; I would have back filled it with coarse material at the base, then progressive finer material going back up so as to let water through rather than forcing water elsewhere potentially causing another sinkhole. Foamed concrete is not always the best solution.

 

[pwhole]

There's plenty of LIDAR-capable drones out there that can do a remote inspection and generate an accurate 3D model of the void without anyone having to go down the hole. The vent shaft in the bottom photo is sealed at surface, so could only be inspected from below, but the brickwork was way too knackered to bolt-climb, so the drone was sent up and built a detailed texture-mapped 3D model in 30 mins.

 

[Huge]

Missing grandmother's body recovered from Pennsylvania sinkhole

 

[Huge]

Another sinkhole in South Wales!

Huge sinkhole appears in woman's garden after Storm Darragh flooding

 

[ChrisB]

Huge, your link doesn't work for me. I think it has a lot of tracking data that's corrupted the url. This should work:

Huge sinkhole appears in woman's garden after Storm Darragh flooding

The sink hole appeared on Saturday following flooding at the back of the woman's house in Gilfach Goch, Rhondda Cynon Taf

www.walesonline.co.uk

 

[alanw]

Another sinkhole in South Wales!

It's in the garden at the back of the houses in the centre of this:

Side by side georeferenced maps viewer - Map images - National Library of Scotland

The Heathlands · Gilfach Goch, Porth

Gilfach Goch, Porth

maps.app.goo.gl

Note the confluence of two streambeds shown on the OS 25" map, which continue underneath the new builds with no obvious sign of a detour watercourse.