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East-West Rail (EWR): Oxford-Bletchley construction progress

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Trainee9

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Bletchley Viaduct: Latest Twitter pictures from 4 May show detail of the OLE inside the box and also a beam finishing off the southern end. (Note that it hides the rebar loops on the 100 other beams). There are finishing beams above both ends, but the southern one is hard to see from outside the site, except for a view of the end from Duncombe Street. There is now fencing on top to deter workers from stepping in the two purposeful gaps previously noted. One photo shows a gap from below with light streaming through.
 

fflint

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A big thank you to our on scene reporters for the informaton and photos. BZ to all.
 

Geogregor

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https://twitter.com/nrairops

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gallafent

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There's clearly a big area of that deck that isn't going to be used for the actual railway alignment, … anyone know what's planned to be put on there? I'd suggest a solar array, or otherwise wildflower meadow!
 

swt_passenger

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There's clearly a big area of that deck that isn't going to be used for the actual railway alignment, … anyone know what's planned to be put on there? I'd suggest a solar array, or otherwise wildflower meadow!
Nothing much, as per the planning drawing I linked in post #12. It is just described as a maintenance area.

I saw on Twitter somewhere a comment asking if it was going to carry the station platforms. o_O
 

snowball

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At the top left of the last picture in #34 it looks as though there's going to have to be an area of supplementary deck to tie in to the approach. It's not yet clear how it will be supported.
 

swt_passenger

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At the top left of the last picture in #34 it looks as though there's going to have to be an area of supplementary deck to tie in to the approach. It's not yet clear how it will be supported.
We discussed this earlier, @mr_jrt noted it in post #11. I believe from the pdf drawing there’s a new pier 20a to go in alongside the covered way, it’s in the side view but not visible in the plan view.
 

Trainee9

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Ah yes, you can just see its corner in the plan view. Thank you.
Regardless of what the draft plan shows, the original Pier 24 is very much in existence and stands a few feet away from the north end of the box, in a suitable position for supporting the connection to the box. Pier 24 can be seen in both of the pictures above. The splaying out and dogleg of the block wall at the other end does not appear on the draft plan either.
 

jfowkes

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It's an extremely substantial structure compared to the old viaduct. Seems like a bit of a waste of materials, but I guess a concrete box is easier to build than a curved bridge structure like the old one?
 

swt_passenger

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It's an extremely substantial structure compared to the old viaduct. Seems like a bit of a waste of materials, but I guess a concrete box is easier to build than a curved bridge structure like the old one?
They also got rid of dangerous support pillars in the 10 foot. They possibly no longer meet new build standards.
 
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Crikey, that's pretty hefty! What is the reason for going for such a large deck rather than a simple bridge the width of the formation?
The extremely shallow angle that the EWR alignment crossed the WCML makes the positioning of intermediate piers almost impossible. The previous structure was highly bespoke in order to achieve this - which is ultimately part the reason it failed. The new structure is very heavy, very solid, very wasteful of material but (and here's the all important part) very low risk for the Structure RAM in the future - and by association the operation of the WCML in particular.
 

mr_jrt

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I kind of feel sorry for the poor people in the houses backing on to the structure who now have a large concrete wall as their view.
 

Sebastian O

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Probably cheaper putting a box over that mucking around with the track alignment, especially at the angle the crossover comes in at.
 

The Planner

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It's an extremely substantial structure compared to the old viaduct. Seems like a bit of a waste of materials, but I guess a concrete box is easier to build than a curved bridge structure like the old one?
Fairly standard design now, a lot of skewed HS2 structures over motorways and rail will be like this.
 

fgwrich

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Crikey, that's pretty hefty! What is the reason for going for such a large deck rather than a simple bridge the width of the formation?

I too am a little surprised, given the extent of work which went into producing a pretty bespoke curved viaduct for the Stockley Flyover. But it's good to see the progress at last.
 

Trainee9

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Correct me if I'm wrong, but one reason for the 'box' design might be to reduce disruption to the main line during construction - a total of three days posession so far. I suspect that the original construction in the 1960s caused far more disruption, even with the low 'health and safety' precautions of the time. Another benefit could be to reduce the risk of a derailment on the EWR line toppling onto the mainline track.
 

Bald Rick

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Correct me if I'm wrong, but one reason for the 'box' design might be to reduce disruption to the main line during construction - a total of three days posession so far. I suspect that the original construction in the 1960s caused far more disruption, even with the low 'health and safety' precautions of the time. Another benefit could be to reduce the risk of a derailment on the EWR line toppling onto the mainline track.

Both correct. Closing the south end of the WCML is not cheap, and whilst this is a big structure, it looks relatively easy to build without much disruption.
 

Freightmaster

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Worth noting that BR took a very similar approach for the Rugby grade separation back in the Sixties, although this is one track over three, with supports in the ten-foot, so much smaller.
The flyover south of Welwyn Garden City is similar:





MARK
 

swt_passenger

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Worth noting that BR took a very similar approach for the Rugby grade separation back in the Sixties, although this is one track over three, with supports in the ten-foot, so much smaller.

There’s loads once you start looking for them, someone mentioned the new Heathrow flyover being unusually a girder bridge, but the old one is a box. Durnford Rd near Wimbledon is another older example.
 

Bald Rick

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Perhaps most similar is the flyover built for Eurostar services at Nine Elms
 

snowball

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I too am a little surprised, given the extent of work which went into producing a pretty bespoke curved viaduct for the Stockley Flyover. But it's good to see the progress at last.

There’s loads once you start looking for them, someone mentioned the new Heathrow flyover being unusually a girder bridge, but the old one is a box. Durnford Rd near Wimbledon is another older example.
Aren't there three Stockley flyovers? The original one, the new one immediately north of the old one, and the other new one a bit further east. Maybe the third has a different name. The first and third are box-type, as is the proposed flyover at Ravensthorpe on the Huddersfield-Westtown scheme.

The latest proposals for HS2 phase 2b seem to include a 3-level structure with two boxes one above the other at Hoo Green, near Mere, Cheshire, where (if NPR also goes ahead) the main western arm trifurcates into routes to Golborne, Manchester and Liverpool. It can be seen in the first of the three maps at this link, between the crossings of the M6 and the A50.

 

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