studiot

What happened to the riverwall?

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Would anyone care to hazard a guess and say why?

riverwall1.thumb.jpg.6b141d301c6bdd8f6b9bec6ea4a48be5.jpg

 

riverwall2.thumb.jpg.5fe67ecdaf5f73ebda895fa1414390bb.jpg

 

riverwall3.thumb.jpg.d85f0d904875c16d6ad0baee920d698e.jpg

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24 minutes ago, pavelcherepan said:

Ground/surface waters washing away the foundation?

Thank you for the reply.

I don't know the answer, hopefully we will find out when they pump out the cofferdam.

However the movement of the wall suggests one thing but the stability of the ground behind it suggests something else.

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Is the water frozen in winter?

(If the river is near your location in your profile then I guess not, according to a quick googling)

 

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24 minutes ago, Ghideon said:

Is the water frozen in winter?

(If the river is near your location in your profile then I guess not, according to a quick googling)

 

Not often, perhaps once in 25 years or so.

The wall has stood several hundred years.

 

The failed section of wall appears to have gone down and moved to the left, parallel to the line of the riverwall, - downriver - both about 75mm.
It doesn't seem to have rotated in any direction or displaced into the river at right angles to the line of the riverwall.
The crack appears sensibly of constant width.

One thing to note is that this side of the river is very shallow and slow running.
Looking at the downstream picture you can see the gravel islands that collect on this side.
This is surprising since the river scour will be least on this side.

There is nothing to suggest the earth behind the wall has become active. If active earth pressure developed, it would be greatest at the bottom so the wall would have rotated outwards at the bottom.

 

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Could be plate tectonics in miniature. You might have the ground settling in chunks, rather than grains, and underground, you could have one layer sliding on another. (over a very long time span)

Pure guesswork of course.

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49 minutes ago, studiot said:

The wall has stood several hundred years.

Was the wall built on top of parts of an older structure? An old wooden construction could possibly have supported the wall for a long time. Here is an example; oxygen-poor and humid environment slows down decomposition of organic material. 

Quote

Houses were built on top of old layers

Approximately every hundred years since Queen Kristina’s sluice in the 1600s, Slussen har been remodeled with new traffic solutions. When the subway and the traffic roundabout was built in the 1930s, it was excavated mostly manually with shovel. Old layers of human activity are therefore left relatively unaffected. New houses and streets were simply built on top of earlier remains.

Garbage with preserved fragrances

With the city’s founding in the 1200s came the garbage. It was thrown not only out on the streets but emptied in the outskirts. Planned ground fillings with old boats, piles and soil were mixed with household waste and sewage. The oxygen-poor and humid environment makes objects from these laysers often surprisingly well preserved. Thanks to the preserved garbage we learn a lot about how people lived in earlier times and also how it could smell!

https://medeltidsmuseet.stockholm.se/in-english/exhibitions/slussen-below-the-surface/

 

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Existing and old abandoned mines, or natural caves, can cause damages like cracks on buildings existing on the surface, when their tunnels are collapsing.

 

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Posted (edited)
1 hour ago, Sensei said:

Existing and old abandoned mines, or natural caves, can cause damages like cracks on buildings existing on the surface, when their tunnels are collapsing.

 

 

2 hours ago, Ghideon said:

 

Was the wall built on top of parts of an older structure? An old wooden construction could possibly have supported the wall for a long time. Here is an example; oxygen-poor and humid environment slows down decomposition of organic material. 

 

Yes some old human relic may be uncovered. I'm sure there are no natural cavities in the gravel and marl of the river bed, which is in the middle of its flood plain extending at least half a kilometre on both sides.

Ghideon,

I remember the refurbishment of the old (13 century) packhorse bridge in Trowbridge, which I underpinned in the 1970s.

A surprise then was the old Roman oak foundations (piles and cross beams) that were in better condition that the stones of the walls (Bath stone).
It was extremely difficult to remove these oak foundations, jack hammers etc just bounded off, unlike with stones.

Edited by studiot

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3 hours ago, studiot said:

The failed section of wall appears to have gone down and moved to the left, parallel to the line of the riverwall

Guesswork from what we have so far: If there was an old wooden wall built before the current one, is it possible that the stone wall was build at exactly the same location? Since the wood under water may have been well preserved it was used as a foundation. Now, after hundreds of years, the old wood is decomposed and cannot support the stone wall. This caused the stone wall section to move almost straight down.

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