What happened to the riverwall?

[dimreepr]

5 minutes ago, studiot said:

A true pedant would include the third possibility of both.

Indeed, but we also deal with probability...

[studiot]

Update pictures.

There has not been sufficient progress to determine anything new.

On 23/08/2018 at 12:56 PM, Ghideon said:

The red arrow shows some sort of structure under water. Does that continue in under the failing part of the wall? If so, is the gap at the green arrow a crack? Does it look like the thing underwater at the red and green arrow has moved down?

However it is clear that the items in the river at the base of the wall that were asked about are sandbags.

 

Here is the site board stating that there was scour and that they will underpin the wall, but this is not certain.
I am trying to see if the masonry below waterline has deteriorated. Lias is not the most durable of building stone.

 

[Ghideon]

2 hours ago, studiot said:

There has not been sufficient progress to determine anything new.

Agree, I can't see anything new. Not sure if it means anything but are there other cracks than the large one?   

[studiot]

This is particularly @Ghideon

Now that that the repair is done and forgotten here is an update.

The river has been in spate over the weir system during the last few days and I observed the different flowpatterns at the failure point abd the rest of the weir sidewalls.

 

The first photo is the normal laminar flow as it tumbles over the weir, ducks down in a U, rises up again and carries on in the same direction.

In the second photo against the failure wall, the water ducks down,  rises backs up and flows back over the top of itself forming a vortex with a horizontal axis perpendicular to the wall.

I have indicated the difference with flow arrows on the pictures.

I would imagine that the vortex picks up small stone which grind against the sidewall constantantly boring into it along the axis line.

[Ghideon]

On 12/26/2022 at 4:31 PM, studiot said:

 

I would imagine that the vortex picks up small stone which grind against the sidewall constantantly boring into it along the axis line.

 

Thanks for the update! I'm vaguely familiar with the results from water vortex and gravel grinding on rock, resulting in a "Giant's kettle" (or "glacial pothole"). So intuitively I would say you are correct but I can't speculate about how strong the effect is or time scales involved to have a visible impact on a construction.

 

(I have been curious about this topic; it was the second thread I interacted in when I joined this forum.)

[studiot]

1 hour ago, Ghideon said:

Thanks for the update! I'm vaguely familiar with the results from water vortex and gravel grinding on rock, resulting in a "Giant's kettle" (or "glacial pothole"). So intuitively I would say you are correct but I can't speculate about how strong the effect is or time scales involved to have a visible impact on a construction.

 

(I have been curious about this topic; it was the second thread I interacted in when I joined this forum.)

Thanks,

Yes the potholes you refer to are the result of a vertical vortex axis.

I am suggesting that in this case the (concrete) bed topography is just right at this location to generate horizontal axis vortices.

I am sorry the photo is not really clear, the river had risen further into full flood by the time I was able to get a camera and photograph it.