Nuneham Viaduct shut - Didcot- Oxford

[DelW]

Maybe a foolish question, but I'd have thought the bridge deck would have twisted with such a drop. Are Network Rail planning to rebuild the abutment but leave the twist or do they have a mechanism to remove the twist through some sort of jacking procedure? I would imagine a bridge of this age not performing so well with the internal stresses of a twist, likewise undoing the twist may do more damage if affected elements not fully strenthened/repaired. It would be worrying to have them just rebuild the abutment and not fix the deck.

The temporary works currently being installed will incorporate jacks, which will be used to raise the deck end back to its original level - or rather a little above, to give clearance for building the replacement abutment. Ultimately the deck should be back at its original level.

There's probably a need to check that the deck members didn't suffer any damage, but I think it's likely that any deflections will have been within elastic limits so will return to their original state when the deck is re-levelled.

 

[stuving]

The bridge deck is solid, (technically it is formed of plates in what is known as as a hog back girder, a mix of arch and tension, not going to bend easily). deck just sits on two ends. This one has two decks sitting on Central pillar, might noy even be physically joined apart from a metal plate over the narrow gap (to stop ballast falling through gap, rather than structural)

Now I would have said exactly the opposite to that - the bridge has almost no strength or rigidity in torsion. It has no lattice members across it to give that rigidity, i.e which would have to change length as the bridge twists. It never needed any, as it was rivetted together in situ (the three girders were assembled on the bank first).

The side girders are wide enough to resist torsion to some extent, and those odd curved members going down to the outer ends of the cross-beams will brace the whole bridge at that point. But they are not going to resist much, because of the geometry - for one thing they are curved!

If you twist the bridge far enough you will tear the rivetted joints, but less than 1 degree over 30 m of length isn't enough to do that. Given the age and condition of the bridge, it would be wise to have a look to make sure. But for the current operations, the thing is essentially floppy when twisted.

 

[30907]

... mistakenly, as arriving into Radley on platform 2.
They seem to be in RTT as Very Short Term, only 2 May. Are they planned to continue - maybe only Mon to Fri ?

Unsurprisingly, no arrival time at P2 was recorded.
I also note that the Culham shuttle didn't run owing to a problem with the unit - and that Appleford isn't being served in either direction after all.

 

[JN114]

Unsurprisingly, no arrival time at P2 was recorded.
I also note that the Culham shuttle didn't run owing to a problem with the unit - and that Appleford isn't being served in either direction after all.

To confirm

The method of working requires Platform 1 to be used at Radley; and Platform 2 to be used at Culham.

Similarly, Appleford would only be able to be served when travelling towards Didcot (due to no Platform
DOO equipment for wrong-direction running); however to keep it simple in an already operationally risky environment and work method Appleford will not be served in either direction.

2 car units only due to position of amended stop markers.

Morning/Afternoon Radley shuttles use the Afternoon/Morning Banbury unit respectively for fuel conservation.

Culham Shuttles rely on Reading having a 12th 2 car available for traffic; which is 100% utilisation of the Reading 2 car fleet (4 Radley/Oxford/Banbury/Worcester, 1 Greenford, 1 Windsor, 2 Marlow/Bourne End, 1 Henley, 1 Basingstoke, 1 Bedwyn, 1 Culham)

 

[Doms1]

Large cranes have been moved into position. Scaffolding has now gone up under the piers on south side and in the centre of the river.

 

[Gagravarr]

Interesting snippet on the grouting work done in the winter in https://www.oxfordmail.co.uk/news/23495390.nuneham-viaduct-early-repairs-stopped-disruption/

Stuart Calvert, capital delivery director for Network Rail, said the movement of the south abutment had been monitored for years.


Repairs were set to go ahead, but when the movement accelerated in February and March this year, the engineers were forced to respond quickly.


It was believed the problem was the unstable ground underneath the south abutment.


To amend this, polymer grout was injected into the ground to allow repairs to the abutment. However, when this took place, the movement accelerated further.


Just a month or so later, the bridge reached the maximum limit of movement and was closed.

Mr Calvert, 59, said: “What we found with the grout was that rather than stopping any movement, the movement accelerated.


“What we don’t know is did that actually cause the movement to accelerate, did it actually slow it down from what it would have done, or did it have no impact at all.


“We genuinely don’t know. It’s a standard way of dealing with this ground stability but it didn’t work. At this stage we just don’t know why.”

 

[Pokelet]

Theres an early Act that gives “railway companies” power of entry to land and property to either deal with accidents or damage, or to prevent accidents or damage. Those powers appear to have been passed down to Network Rail. I recall from previous discussions they would only expect to exercise that right if a landowner refused to negotiate. I believe all statutory undertakers, eg Gas, Water and Electricity networks, also have similar rights of emergency access.

It would appear that any landowner who objected to building a temporary road or such like would need to persuade the Secretary of State that there was an obvious alternative means of access.

I think this is the authority:

I used to own a house that was built on railway land and there was still a very active line behind it. In the deeds it specifically said that a right of access over my land was retained by BR (Western Region). For access to repair, maintain or make safe the Permanent Way.

 

[DelW]

Large cranes have been moved into position. Scaffolding has now gone up under the piers on south side and in the centre of the river.

Interesting choice of crane supplier!

I suppose when you need a big crane at short notice, you have to take whatever's available. If it's on hire for a few weeks, at least the travel time will only be a small proportion of the total hire.

 

[ANDREW_D_WEBB]

Interesting choice of crane supplier!

I suppose when you need a big crane at short notice, you have to take whatever's available. If it's on hire for a few weeks, at least the travel time will only be a small proportion of the total hire.

Part of the Ainscough group which is nationwide so could have come from a closer depot.

 

[Snow1964]

Interesting choice of crane supplier!

I suppose when you need a big crane at short notice, you have to take whatever's available. If it's on hire for a few weeks, at least the travel time will only be a small proportion of the total hire.

James Jack was bought by Ainscough in 2008. Appears they have retained the brand, but I suspect the equipment is pooled when needed quickly

Nuneham is however rather in between their depots at Hayes, Coventry, Southampton and Bristol, and long way from heavy lift depot at Leyland.

 

[zwk500]

James Jack was bought by Ainscough in 2008. Appears they have retained the brand, but I suspect the equipment is pooled when needed quickly

Nuneham is however rather in between their depots at Hayes, Coventry, Southampton and Bristol, and long way from heavy lift depot at Leyland.

There can't be too many cranes that size in the country. Much larger and they may have had to hire one in from Overseas, so perhaps Leyland isn't as bad as it might have been.

 

[snowball]

RAIL #982 has a couple of pages on it. Some of this may have been mentioned upthread. It is estimated to cost £7-10M. They reckon they have an 80% chance of meeting the June 10 target. The temporary river structure rests on 12 piles 15m deep; when finished with they will probably be cut off at riverbed level because it may be too difficult to extract them. The permanent abutment will use 9 piles 25m deep, for which a rig will be borrowed from the Old Oak Common station works.

 

[DelW]

RAIL #982 has a couple of pages on it. Some of this may have been mentioned upthread. It is estimated to cost £7-10M. They reckon they have an 80% chance of meeting the June 10 target. The temporary river structure rests on 12 piles 15m deep; when finished with they will probably be cut off at riverbed level because it may be too difficult to extract them. The permanent abutment will use 9 piles 25m deep, for which a rig will be borrowed from the Old Oak Common station works.

I'm curious to see how the abutment piles will be installed below the deck, even when it's been jacked back up to level. Or possibly they will be installed as two groups, one either side of the deck, with the abutment wall as a deep beam spanning between them. I've never heard of that being done, but there doesn't seem to be any fundamental reason why it wouldn't work. It doesn't seem to square with an odd number of piles though.

 

[stuving]

I'm curious to see how the abutment piles will be installed below the deck, even when it's been jacked back up to level. Or possibly they will be installed as two groups, one either side of the deck, with the abutment wall as a deep beam spanning between them. I've never heard of that being done, but there doesn't seem to be any fundamental reason why it wouldn't work. It doesn't seem to square with an odd number of piles though.

In his video on 28th April, Stuart Calvert said they would "open up parts of the bridge for when we build the new support underneath". So, does that mean removing some of the deck (rivetted iron plates) and driving piles through that space? That would allow piles to be placed on the river side of the bearings as well as on the embankment side, surrounding each of the three bearing points. Assuming the piles are symmetrical, there must be an even number on the river side - presumably four. That would leave five to go beyond the end of the bridge. Simple reasoning says the centre bearing should carry twice the load of each side one, so getting two piles within the bridge outline would be important to support its weight with vertical forces. I'm guessing two more would go each side of the bridge.

 

[DelW]

In his video on 28th April, Stuart Calvert said they would "open up parts of the bridge for when we build the new support underneath". So, does that mean removing some of the deck (rivetted iron plates) and driving piles through that space? That would allow piles to be placed on the river side of the bearings as well as on the embankment side, surrounding each of the three bearing points. Assuming the piles are symmetrical, there must be an even number on the river side - presumably four. That would leave five to go beyond the end of the bridge. Simple reasoning says the centre bearing should carry twice the load of each side one, so getting two piles within the bridge outline would be important to support its weight with vertical forces. I'm guessing two more would go each side of the bridge.

I can see how that pile layout would work, but to get a rig to the front pile locations would presumably mean removing some of the end cross beams as well as deck plates. That might be the only answer though, since I can't think of a type of rig that could have its mast erected through a hole in the deck, other than a shell and auger tripod rig. It would take forever to bore a 25m pile with one of those, if it's even possible, and I think 600mm nominal diameter is their limit.

No doubt there'll be some experienced people devising a method, and I'll be interested to see what they come up with.

 

[zwk500]

I can see how that pile layout would work, but to get a rig to the front pile locations would presumably mean removing some of the end cross beams as well as deck plates. That might be the only answer though, since I can't think of a type of rig that could have its mast erected through a hole in the deck, other than a shell and auger tripod rig. It would take forever to bore a 25m pile with one of those, if it's even possible, and I think 600mm nominal diameter is their limit.

No doubt there'll be some experienced people devising a method, and I'll be interested to see what they come up with.

Is the crane that they have onsite big enough to lift out a deck span, and could one be lifted without damaging it beyond economic use?

 

[swt_passenger]

Is the crane that they have onsite big enough to lift out a deck span, and could one be lifted without damaging it beyond economic use?

It would be odd to announce and then spend so much time and effort building temporary supports in the river, if it was eventually intended to lift a span out?

 

[zwk500]

It would be odd to announce and then spend so much time and effort building temporary supports in the river, if it was eventually intended to lift a span out?

They might lift one span , drill the piles, then put it back on the temporary supports so that it's ready to be reinstated at the earliest opportunity (and the crane can be handed back). It would be unlikely, though cutting out sections of deck also seems somewhat counterproductive.

 

[DelW]

Is the crane that they have onsite big enough to lift out a deck span, and could one be lifted without damaging it beyond economic use?

It would need a detailed survey of the deck, and/or access to original construction records, to calculate the weight with any certainty. Though presumably someone must have had to do that as a basis for the temporary works design.

It's impossible even to estimate it approximately from photographs.

 

[Fidelis]

Latest update from GWR at 13.43 today and the video shows the crane :-

We are preparing to install the temporary structure that will support the weight of the bridge while the abutment is replaced.

The first truss beam was lifted into place Wednesday – first onto the pontoon, then floated under the viaduct into the right position. The second truss beam will be lifted following the same process. All pile caps are now complete and we are on target to have all the beams in the right place in order to prop up the viaduct on Monday.

You can watch the latest video on the repair works here: https://network-rail.wistia.com/medias/8iqvj6qotr and we will continue to provide weekly updates on our progress here https://www.networkrail.co.uk/running-the-railway/our-routes/western/nuneham-viaduct-monitoring-and-stabilisation/

 

[TB]

To confirm

The method of working requires Platform 1 to be used at Radley; and Platform 2 to be used at Culham.

Similarly, Appleford would only be able to be served when travelling towards Didcot (due to no Platform
DOO equipment for wrong-direction running); however to keep it simple in an already operationally risky environment and work method Appleford will not be served in either direction.

2 car units only due to position of amended stop markers.

Morning/Afternoon Radley shuttles use the Afternoon/Morning Banbury unit respectively for fuel conservation.

Culham Shuttles rely on Reading having a 12th 2 car available for traffic; which is 100% utilisation of the Reading 2 car fleet (4 Radley/Oxford/Banbury/Worcester, 1 Greenford, 1 Windsor, 2 Marlow/Bourne End, 1 Henley, 1 Basingstoke, 1 Bedwyn, 1 Culham)

Out of interest, when working wrong line, is a train able to run at line speed (whatever that is here) or is there a lower limit a train has to observe?

 

[The Planner]

Out of interest, when working wrong line, is a train able to run at line speed (whatever that is here) or is there a lower limit a train has to observe?

Depends if there is a specific signed bidi speed. Wrong road is normally 50.

 

[Saj8]

In this case, it is normal line speed in both directions, except for 15 over the points at Kennington junction in the up direction. The line speed is 90 in the down direction (Radley to Oxford) and 60 in the up direction. (Oxford to Radley.)

 

[Boilinthebag]

Curious on the actual working. If it's working to and from a point of obstruction under P1 then the driver would get a SLW by pilot form in the right direction for both directions with signals worked normally and no 15mph limit for points? Can't be a wrong direction with a bi-di line unless signals are only being worked one way.

 

[Benjwri]

Curious on the actual working. If it's working to and from a point of obstruction under P1 then the driver would get a SLW by pilot form in the right direction for both directions with signals worked normally and no 15mph limit for points? Can't be a wrong direction with a bi-di line unless signals are only being worked one way.

The signals can’t be used when working wrong direction towards Radley, because the next signal is over the viaduct and therefore past the point of danger. There isn’t a signal at the end of the Radley Platform 1.

 

[Doms1]

I stress that I'm not involved in this project at all, and thus my answers here are pure educated guesses, but I am a railway engineer and a chartered member of ICE, so here's my thoughts...


Given the timescales that this job was done in, the calculations to work out how many piles would be genuinely needed would take too long, and would involve some pretty big assumptions about the ground type anyway. If this were a project on a normal timescale you'd do some robust ground investigation, but there's no time for that here, plus the ground is known to be settling/moving/substandard because, well...
Accordingly, the design methodology is likely to look more like 'take whatever information we can glean from similar situations and any records we have available. Make some pretty generous assumptions about the loadings and the ground stiffness and stability. Work out the resultant number of piles required. Double or even triple it if the assumptions were big. Go for installation.


Almost certainly 660mm diameter as this was one of the most common pile types used on the electrification project, and thus is probably what was in a store somewhere. The piles look very much like leftover electrification foundation piles - look at the tops - those are screw fixings for OLE mast brackets.

How long - piles were frequently up to 5m long, sometimes longer, so probably about this.
Length was probably also 'driven to refusal', or driven until they were presenting a certain resistance force. By doiing this you can install to a reasonable level of confidnce that the piles can bear a certain amount of weight, and thus would be suitable for the temporary scenario.
This is also supported by the pile tops all being slightly different heights - being driven to a force rather than a depth would mean they all reach that force at slightly different points.


Almost certainly vibrated or hammered (or a bit of both) down. You're putting these into a river bed so you really don't want to be boring or augering if you don't have to.


The designers probably only had a very rough idea of what they could expect for that, hence my above assumption of driving to a force rather than a depth.


Unlikely. If they were filled they would be filled with concrete, which would make removal much harder. Given these are temporary, almost certainly with the river authority demanding a removable solution, you want them to be able to be removed fairly easily, or, if they refuse to come back out again, able to be cut off at the river bed.


My best guess would be something like the 'superprop' from mabey: https://www.mabeyhire.co.uk/MabeyHi...ropping-and-Jacking-Brochure-web.pdf?ext=.pdf
Probably a plan to cut the tops of the piles off at the same level and place some props across the top.
However, there's a plethora of options for this one.

They would also almost certainly have lots of monitoring sensors on the piles and props to ensure he piles don't shift too much when they are loaded.

Not sure exactly which product they are using, but what looks like the Mabey Bridge girders are now in position under the bridge on the piles driven into the riverbed, ready for jacks to be placed. The water main running over the bridge has been cut and removed ready for jacking to begin,I presume.

 

[crablab]

They've jacked the bridge deck successfully today.

 

[swt_passenger]

Interesting pics thanks. So we now know for sure they're not jacking at the very end of the span, which presumably gives much more working room around the existing pier to demolish it?

Does it look as though there’s more jacking force being used under the middle main girder, and is that what would be expected, ie half the overall weight is supported in the centre, and a quarter at each side?

 

[zwk500]

Interesting pics thanks. So we now know for sure they're not jacking at the very end of the span, which presumably gives much more working room around the existing pier to demolish it?

Does it look as though there’s more jacking force being used under the middle main girder, and is that what would be expected, ie half the overall weight is supported in the centre, and a quarter at each side?

The bridge is a separate span for each track isn't it? Looking at those pictures, there are 2 jacks on each side of each span.

 

[swt_passenger]

The bridge is a separate span for each track isn't it? Looking at those pictures, there are 2 jacks on each side of each span.

I think one of the early explanations was that it was built up in situ, ie there’s only three main girders, the central girder is common to both decks.