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Journey by Journey / London to Didcot, Oxford and Banbury / Re: Black Bridge, Nuneham: southern abutment failure
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on: April 13, 2023, 14:24:40
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So maybe they do intend to did a big trench and have a look at exactly what is there, and if it's not what they like replace it.
Site investigations into ground conditions involve a specialist geotechnical company drilling down and collecting core samples. Trench digging is not required, which is just as well because you could be going down 25 metres or more. The cores are laid out and the materials are identified and logged to record the depths at which they occur. The strength and other attributes of the materials found are analysed and noted. This information, along with the load to be supported, is used to design the piles. It is not especially complicated and the conditions at Nuneham are unlikely to be abnormal for the Thames Valley. |
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17
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Journey by Journey / London to Didcot, Oxford and Banbury / Re: Black Bridge, Nuneham: southern abutment failure
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on: April 13, 2023, 11:02:19
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Paul Clifton’s assertion that NR» “..have no idea what the foundations are like.” doesn’t quite square with Electric Train’s comment (post 78) that he is absolutely certain that NR had a plan [for the bridge]
I assume that NR carried out site investigations as soon as the southern abutment began causing concern back in 2018 or before, so they would have known (I hope!) about the ground conditions and the below-ground condition of the abutment well before its recent failure. Presumably these investigations must have shown that a new abutment would be required at some point as the current one isn’t sitting on something solid. Even if design work had not already started on a new abutment before its recent failure, I would have thought that, assuming all the site investigations have already been done, design and construction is achievable within 8 weeks.
Piles will be required of course, though the number, diameter and depth will depend on the ground conditions. Fairly standard civil engineering work.
If there is to be a “temporary” support for the deck in the short term it’ll be interesting to see what form it takes, but I would have thought that would need piles too.
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18
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Journey by Journey / London to Didcot, Oxford and Banbury / Re: Black Bridge, Nuneham: southern abutment failure
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on: April 07, 2023, 10:03:20
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Whitchurch Bridge, which is a 44 tonnes metal decked road bridge over the Thames at Pangbourne, was reconstructed in 2014. At the design stage it was established that the south abutment wasn’t strong enough, so a new abutment was constructed. The geology and quality of the chalk was an issue, which may or may not be the same at Nuneham, but 3 X 900mm piles were required, sunk to a depth of 21 metres.
If new piles are required for a conventional abutment at Nuneham then the bridge deck will need to be removed to give clear vertical space for the drilling rig. But maybe clever NR» bridge engineers have another way of installing a new abutment, eg drilling piles either side of the bridge deck and then casting a beam between them, as Ellendune suggests.
Edit to insert "metal decked".
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19
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All across the Great Western territory / Across the West / Re: May 2023 timetable
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on: February 02, 2023, 11:14:41
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Turning to the Thames Valley, the semi-fast Padd – Didcot services are shown as non-stop ML Padd – Slough (or at least Dolphin Junction) and vv as expected. However, they sit at Reading for up to 14 minutes which makes them largely useless for through journeys between local stations west of Reading and Paddington and vv.
I realise that GWR▸ have to accept that on the RL's between Didcot and Reading there’s a free for all between out-of-path freights and their trains, and that a long layover at Reading on the up at least gives the possibility of punctual departures towards London. But I’ve said many times before the solution is for NR» to sort out the UR and DR between Reading and Didcot. Not straightforward of course, as the XC▸ ’s and freights use bits of other busy lines across the network.
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20
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All across the Great Western territory / Across the West / Re: Four problems that Britain’s crisis-hit railway must solve to survive
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on: January 30, 2023, 10:01:38
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There’s one solution that costs nothing at all, which is to improve the quality of NR» ’s timetabling and regulation to improve the probability of trains running on time. I happen to know Didcot quite well – watching Didcot East on Tratsky or Open Train Times for half an hour or so is quite enlightening. Just one example – 2V21 0835 Banbury - Reading NEVER leaves Didcot Parkway on time, and if you watch you’ll see why.
I’m sure there are many other examples in GWR▸ land and beyond.
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24
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Journey by Journey / TransWilts line / Re: 2022 - TransWilts cancellations and amendments log
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on: September 05, 2022, 14:09:03
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I’m not sure that intending passengers are going to be enlightened by stating that axle counters “…use magnetic fields to help signallers determine a train's location”. The key message should be what they do, not how they do it, so mentioning magnetic fields is not helpful (also some types of axle counter do not use magnetic fields).
So just say “axle counters help signallers determine a train’s location”
However, I applaud the intention to provide more information on the causes of disruption.
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25
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Journey by Journey / Transport for London / Re: Crossrail/Elizabeth Line. From construction to operation - ongoing discussion
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on: August 24, 2022, 10:15:38
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The test running was done at up to 24 tph but they’re starting at 12 tph – looks to be a good idea while they and the passengers settle in.
My concern is when Elizabeth Line trains start running through from the GWML▸ with 24 tph through the core. The EL trains will be sharing the busy UR between Reading and Acton with long and/or heavy freight trains which may arrive at Reading way out of their path. Regulation – if available and attempted - may not always be successful in ensuring EL trains are able to present at Westbourne Park when they are supposed to: we’re talking about maybe a 30 second window here.
If I was planning the EL timetable eastbound from Paddington I would first put in a generous pathing allowance at Westbourne Park for EL trains arriving from the west, and second have an operating plan such that there is always a turnround train ready at Westbourne Park to step up to fill the path of the late running train through the core. The late running train, when it arrives, would then fill the next path through the core and the stepping up would cease. This is the only way to run a reliable 24 tph through the core.
Either way I think that passengers travelling through from the GWML to the core will have to get used to a pause at a red light at Westbourne Park.
When the through running starts on 6th November RTT» is showing that eastbound trains entering the core from the GWML will sit at Westbourne Park for up to 7 minutes for pathing reasons. I think passengers - especially regular passengers - will get a bit fed up with this as they watch trains whizzing past into Padd mainline. |
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27
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Journey by Journey / Transport for London / Re: Crossrail/Elizabeth Line. From construction to operation - ongoing discussion
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on: May 05, 2022, 13:57:04
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The test running was done at up to 24 tph but they’re starting at 12 tph – looks to be a good idea while they and the passengers settle in.
My concern is when Elizabeth Line trains start running through from the GWML▸ with 24 tph through the core. The EL trains will be sharing the busy UR between Reading and Acton with long and/or heavy freight trains which may arrive at Reading way out of their path. Regulation – if available and attempted - may not always be successful in ensuring EL trains are able to present at Westbourne Park when they are supposed to: we’re talking about maybe a 30 second window here.
If I was planning the EL timetable eastbound from Paddington I would first put in a generous pathing allowance at Westbourne Park for EL trains arriving from the west, and second have an operating plan such that there is always a turnround train ready at Westbourne Park to step up to fill the path of the late running train through the core. The late running train, when it arrives, would then fill the next path through the core and the stepping up would cease. This is the only way to run a reliable 24 tph through the core.
Either way I think that passengers travelling through from the GWML to the core will have to get used to a pause at a red light at Westbourne Park.
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All across the Great Western territory / The Wider Picture in the United Kingdom / Re: Masks To Become Compulsory On Public Transport Again
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on: December 04, 2021, 09:00:18
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In case anyone new to this thread is wondering, with some trepidation, what the F word referred to above was, it was in fact…. Fatherland. So hardly a reason to get upset.
But back on the topic. I’m off on the train to Taunton later. I don’t approve of compulsory mask wearing and I don’t like wearing a mask especially as I have glasses and hearing aids. The evidence (as opposed to views) on their usefulness is a bit thin.
However, I will wear a mask on the train as it’s now a legal requirement and I’ve no wish to create difficulties for GWR▸ staff.
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