Nuneham Viaduct shut - Didcot- Oxford

[rower40]

I would need some convincing before I was willing to work under there!

It's fine - they've all got hard hats on.
Health-n-Safety gone mad, innit?

 

[83G/84D]

9th June is what I have heard, not July.

The 9th of June is what is being briefed out today in internal railway communications.

 

[GRALISTAIR]

9 weeks then. Quite a bit should be achievable in that time. Not sure a bridge could be built new to modern safety standards and all the planning crap that would go into it.

 

[fgwrich]

9 weeks then. Quite a bit should be achievable in that time. Not sure a bridge could be built new to modern safety standards and all the planning crap that would go into it.

The plan seems to be to use those 9 weeks to install a temporary structure or affect some temporary repair, while longer term plans to build a replacement within the next year are produced.

 

[Llanigraham]

I know it wasn't as "complex" as this bridge, but how long did it take them to build and fit the new bridge over the River Teme south of Ludlow some years ago? They built a new bridge on land beside the old bridge and I don't remember the line being closed for more than a weekend when they slid it into position having removed the old one.

 

[LNW-GW Joint]

9 weeks then. Quite a bit should be achievable in that time. Not sure a bridge could be built new to modern safety standards and all the planning crap that would go into it.

Lamington took 7 weeks for a complete replacement, in the depths of a Scottish winter.
It was seen as a heroic NR achievement at the time (2016).

 

[Oxfordblues]

Not relevant I know, but the Bailey Bridge at Port Meadow here in Oxford was constructed in just 45 minutes!

 

[WelshBluebird]

Am I being a bit naive to think that it is absolutely amazing the structure was allowed to deteriorate into this state before anything has been done? All the talk about the progressively slower speed limits that have been introduced, surely something should have been started as soon as it was realised there was an issue (so presumably when the speed limits started to be imposed)! As I said maybe I am being naive and loads of other bits of railway infrastructure and in just as bad (or worse) condition!

 

[mcmad]

...

That article has some pictures from across the river, of which this gives the best view:

You can see how both wing walls have been left behind by the sinking of the abutment. But the abutment itself does seem to have sunk as a solid piece, and kept not far off level as it did it.

As usual, there are questions it raises. Such as if the bridge has sunk relative to the embankment, why has that parapet column tilted the other way? And what is that signal doing there?

I notice how the river wall also appears to have deformed significantly but the handrail behind less so.

Am I being a bit naive to think that it is absolutely amazing the structure was allowed to deteriorate into this state before anything has been done? All the talk about the progressively slower speed limits that have been introduced, surely something should have been started as soon as it was realised there was an issue (so presumably when the speed limits started to be imposed)! As I said maybe I am being naive and loads of other bits of railway infrastructure and in just as bad (or worse) condition!

I think you are. As has been posted many time on the thread plans had been developed to stabilise the ground hence why the roadway was already in place but the plan was overtaken by the major failure. Its not a case of bob the builder turning up on the morning and sticking a couple of 2x4's under it.

 

[zwk500]

Am I being a bit naive to think that it is absolutely amazing the structure was allowed to deteriorate into this state before anything has been done? All the talk about the progressively slower speed limits that have been introduced, surely something should have been started as soon as it was realised there was an issue (so presumably when the speed limits started to be imposed)! As I said maybe I am being naive and loads of other bits of railway infrastructure and in just as bad (or worse) condition!

Once the ground starts giving, there's not a lot you can do other than getting heavy equipment in and filling in or digging out the voids. Given they had already built the temporary compound before the bridge gave out, either it moved quicker than they thought or they just got unlucky and couldn't quite mobilise in time.

 

[quantinghome]

Am I being a bit naive to think that it is absolutely amazing the structure was allowed to deteriorate into this state before anything has been done? All the talk about the progressively slower speed limits that have been introduced, surely something should have been started as soon as it was realised there was an issue (so presumably when the speed limits started to be imposed)! As I said maybe I am being naive and loads of other bits of railway infrastructure and in just as bad (or worse) condition!

Something was started - that's why all the temporary access works are in place. You can't just rock up and do something before knowing what it is you need to do. That requires investigation and monitoring and so on to fully understand the problem, then work up a remediation design, then start work on site. Unfortunately the rate of decline of the abutment outpaced the response.

It's hard to judge but there do seem to be an increasing rate of failures on the railway assets which may be linked to lifespan. Some rail formations will be approaching 200 years old.

 

[Snow1964]

Am I being a bit naive to think that it is absolutely amazing the structure was allowed to deteriorate into this state before anything has been done? All the talk about the progressively slower speed limits that have been introduced, surely something should have been started as soon as it was realised there was an issue (so presumably when the speed limits started to be imposed)! As I said maybe I am being naive and loads of other bits of railway infrastructure and in just as bad (or worse) condition!

The structure hasn't deteriorated in the sense of metal has rusted through (like the A363 bridge), but appears to have sunk at one end.

It's not first time an old pier has sunk on a river Thames bridge (that's why Waterloo road bridge was replaced in 1930s). The pier appears to be in one solid piece (even if now moved relative to wing walls). Presumably the foundations are in some sort of waterlogged soft earth which has compressed.

Sounds like work was starting and a compound set up, but bridge moved further and quicker than expected. Each of the spans probably weights about 150 tons (a guess, I don't have details). If by chance two freight trains crossed together, could easily had two loads of 100+ tons on the span.

If the abutment is original (or at least dates back to the 1857 metal viaduct), if not the earlier wooden bridge, then it would never have been designed to carry that much weight, as trains were much lighter then.

There is a possibility that new piled foundations can be built either side of the pier and a transverse beam installed above the now sunken pier, effectively bridging above the sinking pier. Pier probably wont sink much more if all the weight is lifted off it.

 

[GRALISTAIR]

Lamington took 7 weeks for a complete replacement, in the depths of a Scottish winter.
It was seen as a heroic NR achievement at the time (2016).

You are absolutely correct. I had forgotten all about that.

 

[Snow1964]

The plan seems to be to use those 9 weeks to install a temporary structure or affect some temporary repair, while longer term plans to build a replacement within the next year are produced.

Although people have used term Bailey bridge, there is a modern equivalent, the emergency rail bridge, which uses similar components (but bigger, as 4 soldiers carrying them on a battlefield isn't part of the spec). There are illustrations and downloads on the MabeyBridge website

Mabey Universal Emergency Rail Bridge - Mabey Bridge

The Mabey Universal Emergency Rail Bridge system uses standardised, pre-engineered, interchangeable steel components to provide robust, rapid-build solutions for emergency rail bridges.

www.mabeybridge.com

They are listed as rapid build, more like a few days than 9 weeks

 

[snowball]

Here are 2 accounts of the works that were needed at Lamington.

Re-opening Lamington - Rail Engineer

In the Upper Clyde Valley the river snakes between hills and the West Coast main line (WCML) crosses it four times. The four span 101-metre Lamington viaduct is the largest of these crossings. It is all very picturesque, and the sound of the river burbling around the bridge piers is usually...

www.railengineer.co.uk

In the Upper Clyde Valley the river snakes between hills and the West Coast main line (WCML) crosses it four times. The four span 101-metre Lamington viaduct is the largest of these crossings. It is all very picturesque, and the sound of the river burbling around the bridge piers is usually quite restful.

However, when Rail Engineer visited on 22 January, the noise from the River Clyde was much more pronounced and the ambience anything but restful. After overnight rain and melting snow, the Abington river gauge station, six miles upstream from Lamington, was recording the river level as 1.8 metres above datum, compared with its average 0.7 metres. Flooding of the site compound car park showed the rising water level.

Storms Desmond, Eva and Frank resulted in the wettest December since records began and created what the Centre for Ecology and Hydrology (CEH) described as “extraordinary” hydrological conditions. On the day of storm Desmond, river water discharge into the seas around Britain was a third more than the previous maximum. Published CEH statistics show that, during the month, the Clyde’s river flow was a record 249% of its long-term average.

On 30 December, storm Frank brought widespread flooding and disruption to Scotland. The M74 motorway was blocked by a flood at Abington, where the gauge station recorded the Clyde at its highest-ever level – 3.12 metres above datum.

Lamington Viaduct

As a four span 101-metre bridge, the Lamington Viaduct is the largest of 4 west coast mainline carrying railway bridges that crosses the river Clyde

www.amcogiffen.co.uk

As a four span 101-metre bridge, the Lamington Viaduct is the largest of 4 west coast mainline carrying railway bridges that crosses the river Clyde.

Following Storm Frank’s widespread flooding and disruption to Scotland on the 30th December 2015, the Clyde reached its highest-ever recorded level of 3.12m above datum.

After a train reported a dip in the track over the viaduct, examinations discovered that pier 2 had lost structural integrity. AmcoGiffen, with Network Rail agreement, closed the line to all traffic. We were subsequently contracted to secure the viaduct, produce the design and delivery of a reactive solution, and safeguard the structure against future issues.
AmcoGiffen’s Scope of Works

Mobilising on New Year’s Day – shortly after the blockage was reported – our team’s first job was to secure the viaduct. Creating a bespoke design solution, which required works to Pier 2, Pier 3, the North Abutment and all 4 spans, our overall scope of works included:

17,000 tonnes of rock armour protection
Underwater concrete pour of 400m3
Replacement of 4 bearings
Installation of 133 soil nails
Installation of concrete jackets
Bridge deck lifting
A new insitu cast concrete nosing to the upstream side of the pier 3
Associated grouting works
Grey bank protection upstream to both embankments

 

[hwl]

Although people have used term Bailey bridge, there is a modern equivalent, the emergency rail bridge, which uses similar components (but bigger, as 4 soldiers carrying them on a battlefield isn't part of the spec). There are illustrations and downloads on the MabeyBridge website

Mabey Universal Emergency Rail Bridge - Mabey Bridge

The Mabey Universal Emergency Rail Bridge system uses standardised, pre-engineered, interchangeable steel components to provide robust, rapid-build solutions for emergency rail bridges.

www.mabeybridge.com

They are listed as rapid build, more like a few days than 9 weeks

The problems isn't the bridge decks (which can be reused at least in the short/medium term) but the ground under and around the abutment and the first bit of embankment on the south side slumping, talk of bridge decks is a red herring.
Temporary structure = doing something about the southern abutment
The uniformity of the sinking (and continued integrity of the abutment) strongly suggests the saturated soil can not longer withstand the stress (often incorrectly call pressure) as it has done in the past. Quite possibly a head scratching mix of soil moisture content, tree root issues and a little bit of scour (unlikely to be the main cause unless it is over a huge area which is unlikely).
A long term solution is likely to involves very long single spans so the central support can be removed (slight scour risk on south edge) and the new abutments can be further back from the river and far lower risk.

 

[Gloster]

Paul Clifton’s Twitter feed (@PaulCliftonBBC) is saying that the temporary structure will allow limited low speed services. A permanent repair will come later.

 

[BrianW]

Short of looking back over 300/+ posts (sorry!) (please forgive and move on ?)...

IIRC, the 'Stonehaven' flooding/ derailment gave rise to a spate of inspections- from which plans arose? at least for more checking?

The road bridge near Yarnton also testifies to need to investigate potential movements due to excessive water/ rainfall. Oxford clay is very prone to shrinkage and heave.

Hydraulics Research is not faraway at Wallingford- maybe they might help? https://www.hrwallingford.com/

I'm getting pictures of Hatfield, Potters Bar, etc too.

 

[Hellzapoppin]

Of course the problem could be that the abutment isn't sinking but crumbling.

 

[CyrusWuff]

Paul Clifton’s Twitter feed (@PaulCliftonBBC) is saying that the temporary structure will allow limited low speed services. A permanent repair will come later.

Internal info says a week with a 20mph TSR, then normal line speed.

This is, of course, subject to change should things deteriorate further.

 

[stuving]

Sounds like work was starting and a compound set up, but bridge moved further and quicker than expected. Each of the spans probably weights about 150 tons (a guess, I don't have details). If by chance two freight trains crossed together, could easily had two loads of 100+ tons on the span.

If the abutment is original (or at least dates back to the 1857 metal viaduct), if not the earlier wooden bridge, then it would never have been designed to carry that much weight, as trains were much lighter then.

We do know the weight of the 1906-7 bridge: 180 tons for the girders, 325 tons for all the steel. As well as the live loads, there's ballast and track to add to that, and now there's all that extra ballast at the south end as well.

Since the new spans were twice the length (90') of the old ones, they and the whole bridge must have been a lot heavier - well over twice the bearing load, I'd have thought. For that reason alone, the abutment must have been added to, whether or not the old one was left in place inside it.

I still don't think we have direct evidence of that, but the construction sequence provides a hint. They thought it worthwhile to crane the girders into place (slightly offset) before starting demolition. Apart from belt-and-braces reasoning ("let's try it for size before we knock anything down, just to be safe"), I presume that was to reduce the duration of one-track working. The same reasoning would suggest building as much of the new abutment as possible with the old bridge in place as well. Clearly, that limits what can be done.

With under five weeks for the demolish and build phase of each side, I wonder what method would be chosen for the abutment. My guess is a new foundation beforehand, then take down part of the old brickwork and pour concrete for the new one, and face with brick afterwards. But if NR's engineers don't know what's inside it already, they will soon!

 

[XAM2175]

IIRC, the 'Stonehaven' flooding/ derailment gave rise to a spate of inspections- from which plans arose? at least for more checking?

Stonehaven, which is a proper name and so needs no quotes, was the result of defective drainage from off-railway land causing a landslip onto the tracks. The bridge being there was co-incidental, as was the fact that it happened to be receiving attention at the time.

Hydraulics Research is not faraway at Wallingford- maybe they might help? https://www.hrwallingford.com/

No more or less than any other hydrological consultants??

I'm getting pictures of Hatfield, Potters Bar, etc too.

Seriously?

Unless NR is really holding back on information, everything we've seen so far says that the inspection regime worked. The problem was identified in time and it looks very much like the wheels were already turning on getting things sorted. Yes, it would have been preferable to get it sorted before this sort of disruption occurred, but the current situation is still preferable to the alternatives that you have so kindly already described.

 

[Bletchleyite]

You are absolutely correct. I had forgotten all about that.

So how on earth can this take a year?

 

[zwk500]

So how on earth can this take a year?

Because Lavington was washed out by a flood, whereas this is long-term ground movement and so the available options are completely different. But nobody's saying it will take a year, the informed posters upthread were quoting 10 weeks or so.

 

[Bletchleyite]

Because Lavington was washed out by a flood, whereas this is long-term ground movement and so the available options are completely different. But nobody's saying it will take a year, the informed posters upthread were quoting 10 weeks or so.

I saw some stuff on Twitter that was saying that 10 weeks was for a bodge, and a fully new bridge will take a year and will be done once the bodge is in place.

I guess if there's movement they will need to do some deep piling?

 

[GRALISTAIR]

I guess if there's movement they will need to do some deep piling?

And possibly some back-grouting too.

 

[zwk500]

I saw some stuff on Twitter that was saying that 10 weeks was for a bodge, and a fully new bridge will take a year and will be done once the bodge is in place.

That would make sense, as a plan for a long-term fix was in place before the slip happens.

I guess if there's movement they will need to do some deep piling?

Could need to be demolition, digging out, foundation raft, rebuild at the most extreme. Would imagine deep piling and lots of grout being more likely, but it depends what the ground conditions are.

 

[XAM2175]

I saw some stuff on Twitter that was saying that 10 weeks was for a bodge, and a fully new bridge will take a year and will be done once the bodge is in place.

And Lamington wasn't a new bridge, either.

 

[DelW]

I saw some stuff on Twitter that was saying that 10 weeks was for a bodge, and a fully new bridge will take a year and will be done once the bodge is in place.

I've no idea what ""stuff on Twitter" might be or how reliable it is, but installing temporary works should never be a "bodge". It's a specialist discipline in its own right, and is subject to just as much scrutiny of design and installation as permanent works, since lives depend on its adequacy. It just has to be done a lot quicker.

 

[edwin_m]

If the abutment is original (or at least dates back to the 1857 metal viaduct), if not the earlier wooden bridge, then it would never have been designed to carry that much weight, as trains were much lighter then.

It's a masonry abutment, likely to be able to sustain any load ever likely to be put on it as long as the supporting earth doesn't move (which in this case it has).

I'm getting pictures of Hatfield, Potters Bar, etc too.

The one that it reminds me of most is Glanryhd.