Part of the viaduct at Nine Elms has collapsed.

[WAO]

The street view below (sorry about the length) from Google Maps shows what condition the wall was in.

Cantilevered refuges (leaning!). Soft brickwork repaired, surface Portand cement pointing, the inner lime mortar probably gone, external guard rails affixed, etc.

There must be many more like it.

WAO

Google Maps

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[Nicholas Lewis]

The street view below (sorry about the length) from Google Maps shows what condition the wall was in.

Cantilevered refuges (leaning!). Soft brickwork repaired, surface Portand cement pointing, the inner lime mortar probably gone, external guard rails affixed, etc.

There must be many more like it.

WAO

Google Maps

Find local businesses, view maps and get driving directions in Google Maps.

www.google.co.uk

There are far worse than that in and around London Bridge approaches for example. If you zoom in you can see some attempt has been made to cut the buddleia back but that probably just promotes stronger growth. As per NR press release it sounds like a domino effect as once first section falls over (still wouldn't put out plant damage at some point) it just drag the rest of the section over with it as the steelwork acting is acting as lever and then there are some point heating transformers and location cases to give it extra momentum.

Given the age profile of viaducts and that vast amounts of them are above publically accessible spaces this ought to have ORR and RAIB taking a keen interest as to how these are being managed and risk assessed against failure onto these spaces.

 

[HSP 2]

But whats that orange in the forefront of the shot?

When I first seen the video in the small screen size I thought that it was a track side worker that was tethered to the bridge side. Having seen the video on a larger screen I don't think that it is (I hope that it's not). The orange object that I'm talking about starts to move at about 2 sec into the video.

 

[norbitonflyer]

"when the small section failed, the handrail pulled a much longer length down – along the handrail’s entire 70m length".

Suggests the handrail may be over-specified. Surely it only needs to withstand the force of a heavy person falling against it?

 

[BRX]

"we do know that the original collapse was quite small. The wall was connected with a substantial handrail, which was bolted through the bricks, and when the small section failed, the handrail pulled a much longer length down"

A bit of a strange way of describing things. What are they trying to say? That only a very small part of the wall was in poorly maintained condition? It's irrelevant - the entire thing should be designed and maintained to be safe.

Soft brickwork repaired, surface Portand cement pointing, the inner lime mortar probably gone, external guard rails affixed, etc.

There must be many more like it.

There are - I see exactly what you describe, throughout south london.

 

[edwin_m]

"when the small section failed, the handrail pulled a much longer length down – along the handrail’s entire 70m length".

Suggests the handrail may be over-specified. Surely it only needs to withstand the force of a heavy person falling against it?

A bit of a strange way of describing things. What are they trying to say? That only a very small part of the wall was in poorly maintained condition? It's irrelevant - the entire thing should be designed and maintained to be safe.

If a part of the wall failed and the rest was sound then the handrail would most likely have remained in place. The fact it pulled down a section of wall suggests that the whole length was weakened.

 

[BRX]

If a part of the wall failed and the rest was sound then the handrail would most likely have remained in place. The fact it pulled down a section of wall suggests that the whole length was weakened.

Yes, exactly. Or, the strength and stability of the brickwork were not properly taken into consideration in the design of the handrail.

 

[JohnRegular]

At what point would it be decided that such a viaduct requires complete replacement? It would no doubt be a significant undertaking (to put it mildly) but it surely can't be expected that a now 170 year-old structure can continue to support such a heavily used section of railway indefinitely.

 

[HSTEd]

Suppose it's inherent in trying to operate a railway with infrastructure getting close to 200 years old.

 

[BRX]

Suppose it's inherent in trying to operate a railway with infrastructure getting close to 200 years old.

It's only inherent if it's not maintained well.

I know there will be complaints about armchair internet experts, but a look at that Google streetview is enough to show that the brickwork here was not being kept in good condition. You can see that lots of it needs repointing (any house survey, where the brickwork was in this state, would include repointing and repair as a relatively urgent item for attention) and you can even see where buddliea roots have prised a big gap open above one of the arch rings. In fact I think you can see in one of the photos at the beginning of the thread where this has been 'repaired' simply by filling it with mortar (and probably cement based mortar that is not appropriate for this age of brickwork).

 

[edwin_m]

Yes, exactly. Or, the strength and stability of the brickwork were not properly taken into consideration in the design of the handrail.

In the condition it seems to have been in, it would have collapsed sooner or later with or without the handrail. If it was in visibly in a poor condition at the time the handrail was attached then the work should have been suspended until the problem was sorted out.

I think someone also mentioned that the handrail replaced a brick parapet in order to improve clearances, possibly in the early 1990s as part of Eurostar works. I wonder if the loss of the parapet, presumably with capping stones, would have encouraged water ingress, or the vibrations from drilling for the handrail weakened the mortar. If so then it's perhaps a hopeful sign, as most of the many similar structures haven't had this sort of work done so they might remain in a slightly better condition. But I still expect there will be much examining of viaducts going on in South London over the next few days.

At what point would it be decided that such a viaduct requires complete replacement? It would no doubt be a significant undertaking (to put it mildly) but it surely can't be expected that a now 170 year-old structure can continue to support such a heavily used section of railway indefinitely.

The wall that collapsed protects the arches and the infill that support the track from weather damage, but is not in itself structural. I'd like to think that more attention is paid to those elements where a collapse under a train could be catastrophic. The fact they talk about only closing one track, when at least one more is probably supported in an identical way, suggests there is no immediate problem as someone will surely have looked at it very closely. But it's a very pertinent question for the investigation.

 

[InOban]

Given that you've had a lot of rain down south, a good hard frost would be enough to push the facing bricks away from the infill.

 

[BRX]

Looks to me like the parapet was probably lowered a little, and the coping replaced with concrete copings (or is that just mortar spread along the top?).

It so happens that I've been looking quite closely at quite a lot of viaduct parapets recently, for a personal project. Sometimes the original parapet wall is there along with its original coping (which might be stone or enginerring-type brick cappings). Sometimes it's been lowered, sometimes partially, sometimes almost down to the level of the ballast. Sometimes it then has a new, proper coping on it and sometimes it doesn't.

The attached photo was taken from the platform at Loughborough Junction, S London. (This is not the same viaduct as is the subject of this thread, it's just an example.) Looks like the original parapet wall along with its original capping bricks. But it's in very poor condition. Notice the multiple bodged repairs, probably with inappropriate mortar. Parts of the brickwork painted with stuff that might affect its ability to dry out. Multiple bits of metalwork fixed into what doesn't look like secure fixings. The clear need for repointing in parts. Open joints. Spalling on many of the capping bricks. The bricks pushed totally out of place by buddliea growth in the bottom left of the image.

 

[Nicholas Lewis]

Looks to me like the parapet was probably lowered a little, and the coping replaced with concrete copings (or is that just mortar spread along the top?).

It so happens that I've been looking quite closely at quite a lot of viaduct parapets recently, for a personal project. Sometimes the original parapet wall is there along with its original coping (which might be stone or enginerring-type brick cappings). Sometimes it's been lowered, sometimes partially, sometimes almost down to the level of the ballast. Sometimes it then has a new, proper coping on it and sometimes it doesn't.

The attached photo was taken from the platform at Loughborough Junction, S London. (This is not the same viaduct as is the subject of this thread, it's just an example.) Looks like the original parapet wall along with its original capping bricks. But it's in very poor condition. Notice the multiple bodged repairs, probably with inappropriate mortar. Parts of the brickwork painted with stuff that might affect its ability to dry out. Multiple bits of metalwork fixed into what doesn't look like secure fixings. The clear need for repointing in parts. Open joints. Spalling on many of the capping bricks. The bricks pushed totally out of place by buddliea growth in the bottom left of the image.

View attachment 87951

About par for the course around south london not sure about rest of country. Also another thing to factor in is since the structures were constructed the infrastructure to support railway operations has expended with cable routes, signal and there bases, location cases, point heating equipment and the need for safer refuges all disturbing the original structure in some way.

 

[HSTEd]

It's only inherent if it's not maintained well.

This is inherent in structures as they age however, especially ones built from such a relatively primitive construction technology as bricks in mortar.
The maintenance requirements just keep going up and up and up and up.

If you want to eliminate this the only options are to spend an astronomical sum of money trying to underground the section (which I don't think is remotely practical although it is a fascinating engineering challenge) or take the mass disruption of dismantling the viaduct.

Replace it with either a duplex stainless reinforced concrete viaduct or a more radical stainless steel structural viaduct.

Using slab track to eliminate any substrate capable of supporting plant growth.

 

[BRX]

This is inherent in structures as they age however, especially ones built from such a relatively primitive construction technology as bricks in mortar.
The maintenance requirements just keep going up and up and up and up.

If you want to eliminate this the only options are to spend an astronomical sum of money trying to underground the section (which I don't think is remotely practical although it is a fascinating engineering challenge) or take the mass disruption of dismantling the viaduct.

Replace it with either a duplex stainless reinforced concrete viaduct or a more radical stainless steel structural viaduct.

Using slab track to eliminate any substrate capable of supporting plant growth.

Brick and mortar structures can last a very long time with proper maintenance. The requirements don't necessarily have to go up and up. That's what happens when you delay work. Stuff like removing roots is very difficult and disruptive - but if you don't allow the plants to take hold in the first place, then you avoid that difficult work altogether. Likewise if you let mortar joints deteriorate then water starts getting deep into the structure and creates problems that take more work to fix, than the work it would have taken to get them repointed at the appropriate time.

 

[InOban]

A stitch in time saves nine.
All over the network they're having to catch up on deterred maintenance at great cost and disruption.

 

[Nicholas Lewis]

A stitch in time saves nine.
All over the network they're having to catch up on deterred maintenance at great cost and disruption.

For sure negligence on viaduct brickwork could well haunt future generations big time for little effort over the last 30 years

 

[HSP 2]

A cost effete solution to some of the viaduct problems around the south of London, would be to look at using injection grouting to help fill any voided and any wet spots.

But what do I know I'm a mechanical engineer.

 

[Parham Wood]

If a part of the wall failed and the rest was sound then the handrail would most likely have remained in place. The fact it pulled down a section of wall suggests that the whole length was weakened.

Not really relevant but I would observe that the leverage force exerted by the handrail falling would be increased greatly by the weight of the falling masonry attached to the handrail. Nevertheless it is interesting that the handrail further along stayed attached to the brickwork and it looks like the brickwork itself detached pulled by the handrail.

 

[edwin_m]

Not really relevant but I would observe that the leverage force exerted by the handrail falling would be increased greatly by the weight of the falling masonry attached to the handrail. Nevertheless it is interesting that the handrail further along stayed attached to the brickwork and it looks like the brickwork itself detached pulled by the handrail.

Possible that patch repairs were fairly effective at holding together the visible outer layer of masonry, but didn't do anything to keep it attached to the layer behind? In that case it would tend to fall as a big chunk instead of disintegrating into individual bricks - so in that sense maintenance may have made the problem worse.

There are some similarities to this incident: https://www.gov.uk/raib-reports/par...e-onto-open-railway-lines-at-barrow-upon-soar

At around 23:50 hrs on 1 August 2016, a bridge carrying Grove Lane in Barrow upon Soar, Leicestershire, over the Midland Main Line, partially collapsed and a large volume of masonry fell onto the railway lines below. At the time of the collapse, core sampling work was being undertaken to investigate localised subsidence in the footpath on the south side of the bridge. The bridge was closed to the public when the collapse occurred, but the railway lines below were open to traffic.

When the coring had reached about 1.4 metres below ground, water appeared at the surface and shortly afterwards, the adjacent wall fell away from the side of the bridge, taking with it part of the footpath, a length of cast iron water main and the core sampling rig. Five workers were able to get clear as the collapse occurred and no-one was injured. Two of the four railway lines through the bridge were completely obstructed and there was debris on a third. There were no trains on the immediate approach to the bridge at the time of the collapse.

The RAIB investigation found that the incident occurred because the bridge wall, built around 1840, was not designed to resist overturning. It had also been weakened by a full- height vertical crack. The water main, which ran close to the vertical crack, probably had a slow leak which was causing on-going subsidence in the footpath. Prior to 1 August, however, there was no evidence that the wall was at risk of imminent collapse.

 

[WAO]

Perhaps the real culprit is the variable London stock brick whose quality was known to wander, alongside the failure in modern times to use Lime mortar (which can dry out, avoiding frost heave). The original brick has lasted a very long time, all the same.

The better option would be the class A engineering (blue) brick used so well on viaducts, especially in the North. There's even Bramley Fall stone from Bramhope, used recently on Blackfriars Bridge.

There was often good reason for traditional methods and materials.

HNY!

WAO

 

[MotCO]

Network Rail have put out a statement.

Is Network Rail being more open than usual in describing the incident? I, for one, appreciate this level of detail so that you can understand why delays may take place, and how long the disruption may last.

"when the small section failed, the handrail pulled a much longer length down – along the handrail’s entire 70m length".

Suggests the handrail may be over-specified. Surely it only needs to withstand the force of a heavy person falling against it?

I would take the view that if a person did lean against the handrail, whether intentionally or accidentally, then would the wall and handrail collapse and fail in its principle purpose?

 

[Nicholas Lewis]

I would take the view that if a person did lean against the handrail, whether intentionally or accidentally, then would the wall and handrail collapse and fail in its principle purpose?

The handrail needs to be fit for purpose as its presence would indicate to any worker they can lean against it although after tis event many will think twice. It should be examined for its integrity by the structures examination team I would expect but to what frequency i don't know - i believe ladders for signal posts are every six years for instance but are only visual. Only some form of stress test like a pull test used for harnesses securing points in buildings for window cleaners for instance would really indicate integrity though.

 

[BobTaylor]

I was called into Nine Elms on 29/12/20 to assess the damage to the electrical cables, all cables were found to supply the arches that are currently in use by Covent Garden companies, all cables were proven to be dead and generators are now being used in Covent Garden to supply the effected units. Luckily no one was hurt in this incident and the reports of people working trackside was true but no one was hanging onto anyone to save them.

 

[PG]

Luckily no one was hurt in this incident and the reports of people working trackside was true but no one was hanging onto anyone to save them.

Welcome to the forum

As can be seen from the video, which shows two members of the 'Orange Army' vacating a signal cabinet in rather a hurry, I think we can agree that their speedy movement likely saved them from going over the side and sustaining injuries.

 

[norbitonflyer]

The photo at Loughborough Junction. ......Parts of the brickwork painted with stuff that might affect its ability to dry out.

That area is a favourite for graffiti vandalism. There can therefore be several layers of paint on the brickwork as the graffiti themselves are painted over by NR, and this may be repeated several times as the spray painters return to their preferred sites.

 

[BRX]

That area is a favourite for graffiti vandalism. There can therefore be several layers of paint on the brickwork as the graffiti themselves are painted over by NR, and this may be repeated several times as the spray painters return to their preferred sites.

I suspect that in the long term, repeatedly painting over the graffiti does significantly more damage to the brickwork than the graffiti itself.

Walked past the site earlier. They've started to rebuild some of it. Quite interesting to see the multiple differently coloured layers of substrate under the ballast (you can see best in the middle image... light grey ballasts, then dark grey stuff, then a lighter layer, then dark again, then yellow, then red).

 

[Nicholas Lewis]

BRX thanks for posting pictures and keeping us upto date with whats happening. Look like there constructing a whole new layer on the outside of the viaduct given a new arch is showing. This suggests they want something more solid to build on.

 

[BRX]

BRX thanks for posting pictures and keeping us upto date with whats happening. Look like there constructing a whole new layer on the outside of the viaduct given a new arch is showing. This suggests they want something more solid to build on.

I don't think it's an extra layer - I think they are rebuilding what was there previously - on part of it it wasn't just the parapet that came down, but some of that outer layer of brickwork including the outermost edges of the arch rings.