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Author Topic: HST derailment, near Stonehaven, 12th August 2020  (Read 7061 times)
grahame
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« Reply #105 on: January 16, 2021, 05:56:54 pm »

From The Scotsman

Quote
Posting on Twitter, ScotRail wrote: "One of our trains has struck a stag between Blair Atholl & Dalwhinnie.

"It's caused a fault, which our crew are working to fix so we can get the train moving again."

Pictured ... an HST

With the double track mainline to Aberdeen blocked by the bridge collapse, the only way up north is the single track via Pitlochry and Aviemore .... strikes me as a bit similar to rail to The West with a dual track via Taunton, with a single track and hilly alternative via "The Mule" if the main line is down ... what I was writing on this morning.

HSTs were designed to manage the sea wall at Dawlish, but perhaps the outcome in confrontation with a Stag wasn't one of the original design principles!
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grahame
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« Reply #106 on: January 16, 2021, 06:01:03 pm »

Never rains but it pours and keeps pouring

From the Inverness Courier


Quote
A COLLAPSED embankment has forced the cancellation of all trains on part of the Far North Line.

Network Rail Scotland has warned that the closure is expected to remain in place for at least the rest of the Saturday, after an embankment "alongside the line" came away between Fearn and Tain.
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stuving
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« Reply #107 on: January 16, 2021, 10:34:13 pm »

I wonder if they?ve increased the track cant to improve overall line speed?  Does the other side of this bridge still have a bit more parapet above the ballast? 

Would be pretty scary if they?ve just generally increased the ballast depth and it?s introduced a failure mode...

Paul

I thought that was part of it - being on the inside of a curve rather than the outside - but I don't think that's even true. Hard to be sure..

There is a third bridge, between those two, but I can't find a picture nor even what it's called. The names I used were railscot's - basically the nearest house named on the OS map - and on that basis it's either East Carmont or Upper Wyndings. It's even possible the collapse was there, but then the distances given would be even less accurate.
« Last Edit: January 16, 2021, 10:40:15 pm by stuving » Logged
paul7755
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« Reply #108 on: January 17, 2021, 11:54:02 am »

I wonder if they?ve increased the track cant to improve overall line speed?  Does the other side of this bridge still have a bit more parapet above the ballast? 

Would be pretty scary if they?ve just generally increased the ballast depth and it?s introduced a failure mode...

Paul

I thought that was part of it - being on the inside of a curve rather than the outside - but I don't think that's even true. Hard to be sure..

I?m referring just to the latest incident.  AFAICT the BBC photo (reply #97) shows fairly clearly it?s on the outside of a curve?
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stuving
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« Reply #109 on: January 17, 2021, 12:17:57 pm »

I?m referring just to the latest incident.  AFAICT the BBC photo (reply #97) shows fairly clearly it?s on the outside of a curve?

Yes - what I meant was that so was the one rebuilt at West Carmont (not clear as worded, I admit).
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grahame
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« Reply #110 on: January 17, 2021, 09:44:36 pm »

From the Evening Express

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A north-east railway line will be closed this week after part of a bridge wall collapsed ? close to the site of a fatal train crash.

Around 24 metres of the side wall of the bridge at Tewel near Stonehaven gave way on Friday.

It was less than a mile from the site of a fatal derailment which caused the deaths of Donald Dinnie, Brett McCullough and Christopher Stuchbury last August.

Network Rail said it was making good progress on the damage, which it had earlier described as "extensive".

Engineers are facing a number of challenges getting access to the site, including the height and location of the bridge.

As a result, the line between Stonehaven and Montrose will be closed for at least the next week.
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stuving
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« Reply #111 on: January 18, 2021, 12:27:19 am »

NR Scotland's Twitter feed has an aerial picture, showing that in fact none of the lost section of parapet/wall is on the bridge proper:



It's also clear from their comments that "closed for week" does not imply anything about the date of reopening.
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paul7755
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« Reply #112 on: January 18, 2021, 12:48:14 pm »

It all suggests to me that it?s actually a quite different problem to Carmont, where a power car or coaches on their side are believed to have broken away the parapet.   There will be hundreds if not thousands of similarly constructed parapet walls having to cope with a side load from the track formation, and that load may well have been gradually increasing over many years.

Is there usually going to be any sort of lateral reinforcement, or will the standard design be a simple wall, either brick or stone blocks on mortar courses?

Paul
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stuving
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« Reply #113 on: January 18, 2021, 02:54:38 pm »

It all suggests to me that it?s actually a quite different problem to Carmont, where a power car or coaches on their side are believed to have broken away the parapet.   There will be hundreds if not thousands of similarly constructed parapet walls having to cope with a side load from the track formation, and that load may well have been gradually increasing over many years.

Is there usually going to be any sort of lateral reinforcement, or will the standard design be a simple wall, either brick or stone blocks on mortar courses?

Paul


That's pretty much how I see it. The force that pushed it off was quite diffferent, but rebuilding is the same problem. If the formation comes higher up this time, so it's more of a retaining wall, how much difference does that make? Mind you, we don't know whether the new bit at West Carmont is pinned into the formation.

But that does raise an even more general question about such a structure, even further down where it looks solid and only the outside is visible. Just what is behind the neat masonry? How stable is it, and does rainwater get in? You'd hope those looking after them know this sort of thing, though I suspect they may not for some that have never been a problem. But it could turn into another of those circular e-mails dreaded by NR local managers - e.g. "urgent examination required of all masonry acting as a retaining wall even as a secondary function".
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paul7755
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« Reply #114 on: January 18, 2021, 04:56:59 pm »

I think the new stuff below the ballast at Carmont is ?L shaped? concrete blocks, (on their side ie wide base, low wall), presumably for speed of build, but implicit in that is a much stronger parapet.

(Second link in reply #89, or reply #100 is what I?m thinking of.)

Paul
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stuving
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« Reply #115 on: January 18, 2021, 06:46:30 pm »

I think the new stuff below the ballast at Carmont is ?L shaped? concrete blocks, (on their side ie wide base, low wall), presumably for speed of build, but implicit in that is a much stronger parapet.

(Second link in reply #89, or reply #100 is what I?m thinking of.)

Paul

There is a better view in the NR news item - but even the full resolution image doesn't make that 100% clear. Behind the parapet might be concrete "planks" with the wall segments attached, or a poured slab, or even whatever the top of the bridge looks like when cleared but still with some gravel and stuff on it.

I did originally think there was no point going for a much more robust parapet, since having a train at full speed stop more suddenly on the bridge isn't likely to lead to a significantly better outcome. However, stopping a slower derailed train falling off is clearly a good thing, so I can see that the rigidity provided by reinforcement (even if it is only at the base) is worth having.

In that picture you can also see that, when that NR release said "a considerable amount of engineering work is also being carried out to repair and extend drainage systems on the railway track and lineside embankments at the site", they weren't kidding.
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grahame
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« Reply #116 on: January 27, 2021, 08:34:06 pm »

https://www.bbc.co.uk/news/uk-scotland-north-east-orkney-shetland-55828368

Quote
The rail line between Stonehaven and Montrose will be closed until 22 February after a bridge wall collapsed, Network Rail has said.

The 24m (79ft) section of side wall broke on 15 January, about a mile north of where three people died in last year's derailment.

The line had reopened in November, nearly three months after the tragedy.

Network Rail said full structural assessments had been completed by specialist engineers.

Plans are now in place to repair the bridge and reopen the line late next month.
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