Marple lock 11

[magpie patrick]

Lock 11 is currently in bits in the Memorial Park...

[TheBiscuits]

Just now, magpie patrick said:

Lock 11 is currently in bits in the Memorial Park...

Good pictures, but somebody has put slightly different graffiti on each of the stones.  Maybe I should volunteer to clean the paint off ...

[Jen-in-Wellies]

To make the lock walls more resistant to movement in the future they should take the time, while it is in bits, to chisel Lego studs in the blocks.

 

Jen ?

[nicknorman]

They just need to remove all the expanding foam that - unsurprisingly - expanded and pushed the blocks out.

[ditchcrawler]

12 hours ago, nicknorman said:

They just need to remove all the expanding foam that - unsurprisingly - expanded and pushed the blocks out.

They have just pumped one of the Cheshire locks

[furnessvale]

10 hours ago, ditchcrawler said:

They have just pumped one of the Cheshire locks

Did they prop it before pumping?  If not, they have learnt nothing.

 

George

[jhodgski]

On 23/11/2018 at 10:23, nicknorman said:

They just need to remove all the expanding foam that - unsurprisingly - expanded and pushed the blocks out.

Hiya Nick, Is this true?! How do you know / is it something they've admitted? Cheers, James

[nicknorman]

3 minutes ago, jhodgski said:

Hiya Nick, Is this true?! How do you know / is it something they've admitted? Cheers, James

We went through whilst the lock was on “assisted passage” due to it narrowing. We missed the timing and had to spend the night above the lock. The lady who lives adjacent to the lock came out for a chat and told us the story of the expanding foam. When we mentioned this to the volockie the next morning, he denied it and said the lady was a nutter.

 

BUT ... there was a LOT of evidence of expanding foam, coming out of the ground behind the lock walls, coming out if the gaps between the stones. It seemed 100% obvious to me that the lady was absolutely correct and the volockie was either misguided or lying.

[Theo]

Is it all open and properly operational now?  We want to return from the Rochdale via the Ashton and Macc.

 

N

[jhodgski]

2 hours ago, nicknorman said:

BUT ... there was a LOT of evidence of expanding foam, coming out of the ground behind the lock walls, coming out if the gaps between the stones. It seemed 100% obvious to me that the lady was absolutely correct and the volockie was either misguided or lying.

Thanks, Nick. Is any of that evidence available online?

[jhodgski]

1 hour ago, Theo said:

Is it all open and properly operational now?  We want to return from the Rochdale via the Ashton and Macc.

 

N

Yes, I went through about a month ago.

 

Watch out though, as there's been a delay on a swing bring on the Ashton. CRT have taken the lock mechanism away for repair and have secured the swing bridge with a chain and padlock but (you guessed it...) it's a non-BWB padlock, so you can only get through when they've sent their boys down to do the "open sesame" bit... (which, I think, is from 8am to 9am and 4pm to 5pm.)

Edited July 20, 2019 by jhodgski

[Theo]

Which Swing bridge?  Or is there only one on the Ashton?

 

Nick

[magpie patrick]

9 hours ago, nicknorman said:

We went through whilst the lock was on “assisted passage” due to it narrowing. We missed the timing and had to spend the night above the lock. The lady who lives adjacent to the lock came out for a chat and told us the story of the expanding foam. When we mentioned this to the volockie the next morning, he denied it and said the lady was a nutter.

 

BUT ... there was a LOT of evidence of expanding foam, coming out of the ground behind the lock walls, coming out if the gaps between the stones. It seemed 100% obvious to me that the lady was absolutely correct and the volockie was either misguided or lying.

Knowing something about the process and the lady who lives next to lock 11 (I know her personally) I would offer two observations. 

 

First is that the lady is a long way from being an expert or even vaguely accurate on what goes on with the canal - there are many "smile and nod politely" moments when speaking to her.

 

The second is you are overestimating the power of this expanding foam to shift stuff. It fills cavities well, including tiny ones which is why it leaks out through cracks, but unless they put far too much in it won't shift half-ton stone blocks.

 

It's probably an inadequate solution rather than a damaging one, blocks can't move back into the cavity, but they can move forward into the lock, and they do...

[jhodgski]

3 hours ago, Theo said:

Which Swing bridge?  Or is there only one on the Ashton?

 

Nick

It's bridge 15. Here you go: https://canalrivertrust.org.uk/notices/15618-bridge-15-copperus-lane-swing-bridge-ashton-canal .

 

As pointed out to me by another boater, one of the links in the chain is a shackle which you can undo with an adjustable spanner / pliers.

[nicknorman]

5 hours ago, magpie patrick said:

Knowing something about the process and the lady who lives next to lock 11 (I know her personally) I would offer two observations. 

 

First is that the lady is a long way from being an expert or even vaguely accurate on what goes on with the canal - there are many "smile and nod politely" moments when speaking to her.

 

The second is you are overestimating the power of this expanding foam to shift stuff. It fills cavities well, including tiny ones which is why it leaks out through cracks, but unless they put far too much in it won't shift half-ton stone blocks.

 

It's probably an inadequate solution rather than a damaging one, blocks can't move back into the cavity, but they can move forward into the lock, and they do...

The facts are that the lock has been of adequate width for centuries. The lock suffered from voiding behind the stones (due to not keeping the stonework properly pointed). Whilst the flight was being worked on further up, they took the opportunity to inject “grout”, aka expanding plastic foam, into the cavity behind the locks walls. Sufficient foam was injected to cause it to push up the soil and burst out of the ground behind the lock walls. That was plain to see.

 

Perhaps it was a coincidence that at that point, the stones decided to move inward restricting the lock width and making it unusable. And when CRT jacked the stones out again, they just slid back in again restricting the lock width. The only way it was resolved was by dismantling the lock walls and removing the foam.

 

So perhaps all that was nothing to do with using plastic expanding foam. Perhaps instead it was aliens using a tractor beam from space to pull the walls in. But on the balance of probabilities I think I will go with the most obvious cause.

 

You will of course be aware of the equation “force = pressure x area”. And so with a large area (the entire lock wall) quite a modest pressure from the expanding foam, can create a very large force.

Edited July 21, 2019 by nicknorman

[magpie patrick]

7 minutes ago, nicknorman said:

The facts are that the lock has been of adequate width for centuries. The lock suffered from voiding behind the stones (due to not keeping the stonework properly pointed). Whilst the flight was being worked on further up, they took the opportunity to inject “grout”, aka expanding plastic foam, into the cavity behind the locks walls. Sufficient foam was injected to cause it to push up the soil and burst out of the ground behind the lock walls. That was plain to see.

 

Perhaps it was a coincidence that at that point, the stones decided to move inward restricting the lock width and making it unusable. And when CRT jacked the stones out again, they just slid back in again restricting the lock width. The only way it was resolved was by dismantling the lock walls and removing the foam.

 

So perhaps all that was nothing to do with using plastic expanding foam. Perhaps instead it was aliens using a tractor beam from space to pull the walls in. But on the balance of probabilities I think I will go with the most obvious cause.

 

You will of course be aware of the equation “force = pressure x area”. And so with a large area (the entire lock wall) quite a modest pressure from the expanding foam, can create a very large force.

Wrong on many points

 

The walls of Marple Locks are not pointed and never have been

 

Marple Locks have leaked through their masonry ever since they were built

 

The foam is to stop the voids filling with water, which enlarges the voids and causes instability - the most dangerous feature of the voids is they migrate upwards to ground level at which point people fall into them

 

This is not the first time in their history that Marple Locks have needed attention - the original management committee expressed concerns over their design and depth

 

This wasn't the only lock that had the foam grout applied

 

Given that the lock took a few weeks to fail once the canal reopened it is at least as plausible that the earth behind the walls dried out whilst the lock was out of use for over a year, and then when repeatedly wetted expanded again. ("Caisson Lock Syndrome, for those who know the Coal Canal)

 

A bigger, and more realistic, fear is that in the next ten years two or three more locks will move inwards - they are all the same age and whilst some have had attention over the two centuries they've been around, others have not.

[nicknorman]

1 hour ago, magpie patrick said:

Wrong on many points

 

The walls of Marple Locks are not pointed and never have been

 

Marple Locks have leaked through their masonry ever since they were built

 

The foam is to stop the voids filling with water, which enlarges the voids and causes instability - the most dangerous feature of the voids is they migrate upwards to ground level at which point people fall into them

 

This is not the first time in their history that Marple Locks have needed attention - the original management committee expressed concerns over their design and depth

 

This wasn't the only lock that had the foam grout applied

 

Given that the lock took a few weeks to fail once the canal reopened it is at least as plausible that the earth behind the walls dried out whilst the lock was out of use for over a year, and then when repeatedly wetted expanded again. ("Caisson Lock Syndrome, for those who know the Coal Canal)

 

A bigger, and more realistic, fear is that in the next ten years two or three more locks will move inwards - they are all the same age and whilst some have had attention over the two centuries they've been around, others have not.

Are you saying that Marple lock walls are just a bunch of shaped stoned piled on top of each other with no mortar etc? Seems a bit unlikely but I’m not in a position to argue. But either way, it doesn’t affect my point.

 

According to the CRT bod the lock was not out of use whilst the other bit of the flight was being repaired, it was used by a work boat fairly often. And how come only that lock has narrowed  when the other “out of use” locks haven’t. Seems a strange coincidence that that is (was) the only lock with visible foam coming out out of the ground, and also the only one to narrow.

 

You are saying yes the expanding foam was used on that lock and yes that was the only lock to narrow, but those two facts are coincidence and not related. I find it hard to believe.

[Captain Pegg]

40 minutes ago, nicknorman said:

Are you saying that Marple lock walls are just a bunch of shaped stoned piled on top of each other with no mortar etc? Seems a bit unlikely but I’m not in a position to argue. But either way, it doesn’t affect my point.

 

According to the CRT bod the lock was not out of use whilst the other bit of the flight was being repaired, it was used by a work boat fairly often. And how come only that lock has narrowed  when the other “out of use” locks haven’t. Seems a strange coincidence that that is (was) the only lock with visible foam coming out out of the ground, and also the only one to narrow.

 

You are saying yes the expanding foam was used on that lock and yes that was the only lock to narrow, but those two facts are coincidence and not related. I find it hard to believe.

Pointing a retaining wall does little for its strength since mortar and mortar joints have little to no tensile strength and anything that resists bending has to be able to withstand both tension and compression. In brickwork the mortar is necessary to hold the bricks apart as much as stick them together and it allows the compressive load to be distributed without causing the bricks to fail locally. Stone retaining walls without pointing most definitely do exist but since stone lock chambers are relatively rare Marple may be fairly unique.

 

The advantage of an unpointed wall is that it drains water and so alleviates additional pressure due to pore water in the soil acting on the wall. The disadvantage is that over time the voids clog up and pressure does build up. What may happen after pumping in foam is that the way the wall behaves could change because it would potentially be loaded in a different way. So perhaps consideration to how Marple might respond compared to a pointed brick chamber is a relevant issue. I too am a bit sceptical about expanding foam shifting walls as a direct consequence. It has little mass and is cohesive once it’s set, however it may also be impermeable depending on the cell structure and that could affect the loading on the wall and therefore it’s behaviour.

 

JP

Edited July 21, 2019 by Captain Pegg

[nicknorman]

13 minutes ago, Captain Pegg said:

Pointing a retaining wall does little for its strength since mortar and mortar joints have little to no tensile strength and anything that resists bending has to be able to withstand both tension and compression. In brickwork the mortar is necessary to hold the bricks apart as much as stick them together and it allows the compressive load to be distributed without causing the bricks to fail locally. Stone retaining walls without pointing most definitely do exist but since stone lock chambers are relatively rare Marple may be fairly unique.

 

The advantage of an unpointed wall is that it drains water and so alleviates additional pressure due to pore water in the soil acting on the wall. The disadvantage is that over time the voids clog up and pressure does build up. What may happen after pumping in foam is that the way the wall behaves could change because it would potentially be loaded in a different way. So perhaps consideration to how Marple might respond compared to a pointed brick chamber is a relevant issue. I too am a bit sceptical about expanding foam shifting walls as a direct consequence. It has little mass and is cohesive once it’s set, however it may also be impermeable depending on the cell structure and that could affect the loading on the wall and therefore it’s behaviour.

 

JP

Agreed about pointing/mortar adding strength (or not). I would have thought it was more about waterproofing. By not having the seams sealed, water freely enters and exits the area behind the wall on each fill/empty of the lock, gradually flushing out the soil /loose material and creating a void.

[Mike Todd]

We came up Ashton and Marple a few days ago.

 

The swing bridge is opened for the two windows mentioned - we went through 15 minutes early when the CaRT person turned up early but also be aware the Notice asks boats to be there at the start of the window - we think we saw the same chap a short time later at the top lock, well before the posted window end.

 

When we came through Marple flight, Keir and CaRT teams had just started work on an investigation of a complaint from the neighbour to lock 11 that water was leaking from the lock into their garden. The teams were very confident that it was not from the lock (they were  very familiar with the recent re-build) and suspected another source. They wanted to determine whether it was from the bywash so were digging a series of boreholes. Had I known the tales described above I might have been tempted to probe a few more questions!

 

Incidentally, we found all of the staff on the two canals very pleasant, helpful and most chatty (ruined any kind of schedule that we might have been on!) I learnt new things from them. But this is nearly always my experience anyway.

 

I was not looking especially for the pointing but did notice how well dressed the facing stones were, each with an individual mason's mark. There was little room for adding pointing!

 

[ditchcrawler]

49 minutes ago, Mike Todd said:

We came up Ashton and Marple a few days ago.

 

The swing bridge is opened for the two windows mentioned - we went through 15 minutes early when the CaRT person turned up early but also be aware the Notice asks boats to be there at the start of the window - we think we saw the same chap a short time later at the top lock, well before the posted window end.

 

When we came through Marple flight, Keir and CaRT teams had just started work on an investigation of a complaint from the neighbour to lock 11 that water was leaking from the lock into their garden. The teams were very confident that it was not from the lock (they were  very familiar with the recent re-build) and suspected another source. They wanted to determine whether it was from the bywash so were digging a series of boreholes. Had I known the tales described above I might have been tempted to probe a few more questions!

 

Incidentally, we found all of the staff on the two canals very pleasant, helpful and most chatty (ruined any kind of schedule that we might have been on!) I learnt new things from them. But this is nearly always my experience anyway.

 

I was not looking especially for the pointing but did notice how well dressed the facing stones were, each with an individual mason's mark. There was little room for adding pointing!

 

I photographed lots of the Mason marks down there and put them in my blog https://nbharnser.blogspot.com/2017/06/romiley-monday-26-june-2017.html

[magpie patrick]

2 hours ago, nicknorman said:

Agreed about pointing/mortar adding strength (or not). I would have thought it was more about waterproofing. By not having the seams sealed, water freely enters and exits the area behind the wall on each fill/empty of the lock, gradually flushing out the soil /loose material and creating a void.

Yep, and do that for 200 years...

 

Marple Locks were so bad that at one point BW gave up and cut channels in the towpath for the water to run down - most of it doesn't escape back into the lock but the other way

[alan_fincher]

Perhaps the original construction of Marple locks had no mortar between the blocks, as Patrick suggests, but it is very obvious that the rebuilding has used some kind of mortar.  It is actually leeching out material that is running down over the stones from each mortar course, and staining them.