Black Bridge, Nuneham: southern abutment failure

[whole diary]

[ellendune]

The problem with most piling rigs is not the width and length, but the height of the rig.  Piling underneath a bridge is therefore a big problem.  Less so with the permanent structure will be piled from the south end of the bridge. 

[Mark A]

Ah, I now have a mental image of the bridge span supported at its centre from the river bed, then the span raised slightly and on a turntable - and for a month or so a swing span joins the list of Thames bridge types as it frees up headroom for the work to the abutment.

Also, I thought of the Severn Rail bridge, and the temporary support constructed for the span alongside the damaged pier that had ended up a couple of feet out of true. It's somewhat visible in the photo below. Always wondering how this sort of work is seated on a river bed. That river bed particularly...

Mark

https://www.steampicturelibrary.com/places/bridges-viaducts-tunnels-severn-railway-bridge/dismantling-severn-railway-bridge-1967-8942599.html

[ellendune]

Ah, I now have a mental image of the bridge span supported at its centre from the river bed, then the span raised slightly and on a turntable - and for a month or so a swing span joins the list of Thames bridge types as it frees up headroom for the work to the abutment.

I don't think there is any need to swing the bridge.

If you put a row (or two) of vertical piles immediately south of the bridge span and a further row of raked piles (piles angled slightly out into the river) starting from the same position. then by the time you get to the level just below the towpath - which is the level where you would cast the pile cap You will then you have a slab that is directly underneath bridge bearings.  The pile cap is the thick slab that joins all the piles together at the top spreading the load between them.  You could also put some larger piles at the ends (on the east and west side of the bridge).  The raked piles will also take some of the horizontal load from the ground behind the abutment wall. 

[Gordon the Blue Engine]

Here's a video showing how piling is done in and next to a river:

 https://www.youtube.com/watch?v=q_vH6MMGN1s&list=UUB2nPWt7H4Oai9C0pgfACgA&index=3

Nick Brazil produced videos (on YouTube) at every stage of the reconstruction of Whitchurch Bridge, which has some parallels with that at Nuneham   A big crane on a pontoon was used throughout the project.

[Gordon the Blue Engine]

The length of the pile casings is determined by the ground conditions as determined by site investigations.  They go down as far as is necessary to ensure that the ground will not collapse inwards when the drill exits the bottom of the pile casing.  The drilling continues on downwards as far as is necessary for the loads to be supported.

It’s always good to get the void filled with the steel reinforcing and concrete as quickly as possible, until you do there’s always a concern that the void will collapse inwards. 

[ellendune]

You can see from the video the clear height needed for the piling work. 

[stuving]

There was a reasonably factual piece about this poor old bridge and the work it needs in today's Sunday Times. The one bit of new information, however, I rather doubt: "Fissures have also appeared in the brick arches." Given it also refers to the northern abutment being rebuilt in brick in 1929, the author seems to have a rather hazy notion of the viaduct's component parts.

It gives what is now Network Rail's preferred excuseexplanation for this becoming an emergency repair: "the only part of the bridge that has largely been left untouched since Victorian times is the abutment on the south bank and that has been blamed for the movements that have twisted the railway lines above." It adds: "It is not known why the abutment was not replaced in 1929, although it is likely that it was to save money in those straitened times."

Well, given the 1929 work was all on the north side (and we don't know why or how that was done), why would the abutment alone be rebuilt if it was showing no signs of degradation? No doubt it should have asked why it was not replaced in 1906/7, but the "still looks OK" argument also holds then. Plus, with the demand to keep one line open throughout, rebuilding it would mean taking down half the old abutment and digging half a new foundation at a time - I can see that being worth avoiding.

Note that the new piers mid-river and on the north bank were built in between the existing piles: see OS^▸ (Ordnance Survey) plan views from 1898 and 1910. There were eight spans and seven rows of piles in the old viaduct, but only the cutwaters around the ones in the river can be seen. And no, it's not perfectly accurate and to scale; these small details were drawn freehand.

[stuving]

There was a reasonably factual piece about this poor old bridge and the work it needs in today's Sunday Times.

There's a longer version of that article on the Times/ST website (subject to the usual paywall and marketing offers).

[grahame]

From Oxfordshire Live

Chiltern Railways has advised customers to expect busier trains than usual between Oxford and London Marylebone from Monday (April 17).

Great Western Railway (GWR^▸ (Great Western Railway)) is unable to operate any trains between Oxford and Didcot Parkway until the June 10 at the earliest whilst urgent Network Rail repairs to a bridge are taking place. This means that Chiltern Railways will be the sole option for direct rail travel between Oxford and the capital.

If the trains are likely to be busier than usual, can they operate with longer trains than usual?  The Chiltern fleet is turbo based as I understand it, and the GWR trains that can't run to Oxford via Didcot at the moment include turbos ...

[ChrisB]

This is what Chiltsrn have done, but are warning Oxford commutdrs that these longer trains will be just as busy if they all aim for a train at their usual time. They just cannot put on 9/10 car services.

They have also removed many intermediate stops to help prevent overcrowding. I feel for those few who commute intermediately, like OXF^» (Oxford - next trains)/OXP/BIT to say HDM or HWY, which is now no longer possible at many times of the day. I have pointed this out to Chiltern

[IndustryInsider]

The GWR^▸ (Great Western Railway) Turbos working the Didcot services number three 2-car units and they also work the services through to Banbury, and the halts service on the North Cotswold line, so a maximum of two would be available, one in the peaks. 

They have sufficient differences to the Chiltern units to make them awkward to operate in multiple (no ATP^▸ (Automatic Train Protection), different PIS^▸ (Passenger Information System) systems, minor control differences) so I can’t see Chiltern bolstering their services with them.

With Chiltern being maxed out, the only solution I can see is to run IET^▸ (Intercity Express Train)’s through to London via High Wycombe.  That would need a Chiltern/freight driver to pilot a GWR driver and might need route clearance certification, so I think that is probably more unlikely than likely.

An awkward situation for Chiltern and it’s passengers to have to put up with, but at least the line is available.  Had this happened a few years ago, there would have been no alternative route from Oxford to London of course.

[Marlburian]

On a personal note, I'm due to meet a cousin in Oxford in mid-May (she's probably travelling by train from North Wales) and I may need to visit a hospital in the NE of the city around the same time. So I'm deliberating over the best way to get there, balancing the need to allow for delays  against hanging around for a while if the journey goes smoothly! The hospital car-park has negative reviews for not being big enough.

I'm not keen on crowding on to a replacement bus at Didcot along with disgruntled Cross-Country travellers, and the X40 bus service from Reading offers a long-winded 90-minute journey. So possibly I'll take a taxi from Didcot, drive to a village or town(Wallingford) to pick up the X40, or use one of the Oxford park & rides. At least for the initial hospital visit I won't be having any tests that preclude driving.

[ChrisB]

As someone with recent experience of the JR in Oxdord, if you are looking at a weekday, I would use the Park & Rides. Most of them now have buses from there to the JR, and routes to/from the city centre from the JR.

Weekends are different in that the P&R^▸ (Park and Ride) services to the JR are fewer, but you’ll always get a car park space at weekdnds (£1.40/hour)

[DaveHarries]

I'm not keen on crowding on to a replacement bus at Didcot along with disgruntled Cross-Country travellers, and the X40 bus service from Reading offers a long-winded 90-minute journey. So possibly I'll take a taxi from Didcot, drive to a village or town(Wallingford) to pick up the X40, or use one of the Oxford park & rides. At least for the initial hospital visit I won't be having any tests that preclude driving.

Whereabouts are you travelling from? Given your username I would suggest Marlborough (nr. Swindon) in which case GWR^▸ (Great Western Railway) advise - https://www.gwr.com/oxford-update - that Service S6 (Swindon - Oxford, via. Farringdon) has an acceptance in place for rail tickets. Nice trip tbh which takes about 1½ - 1¾hrs depending on the time of day and I prefer it to a train trip if time allows. Also the S6 between Swindon and Oxford runs more frequently than the Didcot - Oxford service. The S6 is currently not going into Oxford City Centre though due to the work on the rail bridge by Oxford station.

Dave

[paul7575]

Whereabouts are you travelling from? Given your username I would suggest Marlborough (nr. Swindon) in which case GWR^▸ (Great Western Railway) advise - https://www.gwr.com/oxford-update - that Service S6 (Swindon - Oxford, via. Farringdon) has an acceptance in place for rail tickets. Nice trip tbh which takes about 1½ - 1¾hrs depending on the time of day and I prefer it to a train trip if time allows. Also the S6 between Swindon and Oxford runs more frequently than the Didcot - Oxford service. The S6 is currently not going into Oxford City Centre though due to the work on the rail bridge by Oxford station.

Dave

I see they still explain on the GWR site that it’s closed for “detailed safety inspections”. Why can’t they admit in writing that it’s completely failed and they’re now awaiting repair?