Dawlish sea wall collapse

455driver · 27 Feb 2014

Taunton said:
I really can't understand why slab track is not used here. How many times has the ballast been washed away over the years? I did hear that, this storm aside, there is a full time PW gang on the section just to maintain all the issues that arise on it.

How is the concrete slab going to be supported?
What happens when those supports are washed away/undermined?
How long would the line be closed while the supports/slab is repaired compared to the current method of throwing some ballast in the hole? Current breach excepted because that certainly isnt normal.

Concrete slab track is only normally used where the underlying ground doesnt move (tunnels etc), that certainly isnt the case at Dawlish.

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YorkshireBear · 27 Feb 2014

455driver said:
How is the concrete slab going to be supported?
What happens when those supports are washed away/undermined?
How long would the line be closed while the supports/slab is repaired compared to the current method of throwing some ballast in the hole? Current breach excepted because that certainly isnt normal.

Concrete slab track is only normally used where the underlying ground doesnt move (tunnels etc), that certainly isnt the case at Dawlish.

^^ that too... Concrete slab takes longer to repair upon ground movement where the inflexibility of concrete will do a fair bit of damage. Think that is probably a much better reason than mine now i think about it.

Taunton · 27 Feb 2014

This is all stuff that a marine civil engineer will just understand how to handle to create a permanent structure. Most of the sea walls, piers, etc around the coast don't move through storms, they were just designed adequately.

Who remembers the "expert" national marine engineers who got a Network Rail (maybe Railtrack, it was around the time of the changeover) job to fix Dawlish supposedly for all time, which cost a lot. Since then, we seem to have more disruption than ever before on this length.

eastdyke · 27 Feb 2014

455driver said:
How is the concrete slab going to be supported?
What happens when those supports are washed away/undermined?
How long would the line be closed while the supports/slab is repaired compared to the current method of throwing some ballast in the hole? Current breach excepted because that certainly isnt normal.

Concrete slab track is only normally used where the underlying ground doesnt move (tunnels etc), that certainly isnt the case at Dawlish.

The underlying foundations at Dawlish have not moved.

The stone/rubble filled containers are currently sitting on the underlying structure.

YorkshireBear · 27 Feb 2014

eastdyke said:
The underlying foundations at Dawlish have not moved.

The stone/rubble filled containers are currently sitting on the underlying structure.

Hasn't stopped the stuff on top of it moving though. Also the repairs due to lateral damage from landslides will be harder to repair too, concrete really does not like to be bent at all.

Goatboy · 27 Feb 2014

Whats going on with rail service between Newton Abbot and Plymouth? The FGW site implies it's open for trains but if you plan a journey on a Sunday it only offers buses. Is this an NRES error or are they not running trains on Sundays for some reason?

Rich McLean · 27 Feb 2014

Goatboy said:
Whats going on with rail service between Newton Abbot and Plymouth? The FGW site implies it's open for trains but if you plan a journey on a Sunday it only offers buses. Is this an NRES error or are they not running trains on Sundays for some reason?

I believe there is/was scheduled engineering work planned over that section, however, that may now have been shelved

455driver · 27 Feb 2014

It was all buses last Sunday as well.

eastdyke · 27 Feb 2014

YorkshireBear said:
Hasn't stopped the stuff on top of it moving though. Also the repairs due to lateral damage from landslides will be harder to repair too, concrete really does not like to be bent at all.

This picture taken 19th Feb, from the Network Rail Dawlish page, shows just how the wave energy has exploited the weakness of the 'sea wall' track bed support where the walkway was not near full height.

http://www.networkrail.co.uk/assets...4314/fbafc757-3304-444a-bfe3-c8cdc0580541.png

The underlying stuff looks pretty good to my untrained eye. It remains to be seen as to whether or not the walkway will be built up along this section to provide the same protection that has been afforded to the sections where the damage was less serious.

There should not be any landslides at this particular point.

YorkshireBear · 27 Feb 2014

No i see what you mean about the base being good. But the stuff on top of that moved.... Which is what the slab track would rest on...

eastdyke · 27 Feb 2014

YorkshireBear said:
No i see what you mean about the base being good. But the stuff on top of that moved.... Which is what the slab track would rest on...

I am sure that the new 'sea wall' track bed support will not be built of stones and mortar.

I think that Network Rail and their Contractors are doing an absolutely fantastic job, and of which I am sure that the adjacent residents will eventually be extremely thankful.

YorkshireBear · 27 Feb 2014

eastdyke said:
I am sure that the new 'sea wall' track bed support will not be built of stones and mortar.

I think that Network Rail and their Contractors are doing an absolutely fantastic job, and of which I am sure that the adjacent residents will eventually be extremely thankful.

They are not replacing the whole sea wall though...

I never questioned that... i was simply arguing why slab track would not be a great idea.

Taunton · 27 Feb 2014

If it was me I would build the seaward side wall much higher and extend the beach foundations (visible as exposed in the photo linked above) to give an even more solid protection, maybe even caging over the most exposed part. Afraid both train passengers and the house owners would lose their sea view, but that's how it is. Even with the extent of piling, re-bar and concrete required, it would cost a fraction of both money and time compared to the supposed Okehampton scheme (useless) or boring a tunnel back inside the Dawlish cliffs.

eastdyke · 27 Feb 2014

YorkshireBear said:
They are not replacing the whole sea wall though...

I never questioned that... i was simply arguing why slab track would not be a great idea.

Yes - very true.

I expect when the emergency is over that there will be a new resilience survey of the whole of the coastal route. I anticipate that survey will look very closely at the entire section where the pathway is at the lower level.

Goatboy · 27 Feb 2014

455driver said:
It was all buses last Sunday as well.

Can't catch a break, thoroughly bored of RRB's!

D1009 · 27 Feb 2014

At least XC are running trains to and from Exeter this Sunday.

PHILIPE · 27 Feb 2014

Rich McLean said:
I believe there is/was scheduled engineering work planned over that section, however, that may now have been shelved

There are no timetabled trains over the route for period of Timetable from 16 February to 23 March due to Engineering Work. Nothing to do with Dawlish at all

Goatboy · 27 Feb 2014

PHILIPE said:
There are no timetabled trains over the route for period of Timetable from 16 February to 23 March due to Engineering Work. Nothing to do with Dawlish at all

I guess its better they keep it in place because a few more buses when the entire place is bus-city is far less annoying than yet more buses once Dawlish re-opens.

PHILIPE · 27 Feb 2014

The Timetable indicates the work could be anywhere between Exeter and Plymouth.

Graiser · 27 Feb 2014

Paul Sidorczuk said:
What length of sea front is being attended to by Amco Rail ?

110 metres on the main breach
--- old post above --- --- new post below ---

John Webb said:
The "Dawlish Rail: 500m of wall still missing" is actually closer to Teignmouth on the section between Parsons tunnel and Sprey Point. Shame the video doesn't make that clear to help show just how complex NR's repair problems are!

Mainly parapet wall in the sprey point area
--- old post above --- --- new post below ---

edwin_m said:
According to someone in the know who posts on RMWeb, the concrete will be built up to formation level and then conventional ballast and track laid on top.

I would expect that they are just getting the job done and the cost won't be counted until it is finished.

You are correct regarding the track installation, all costs are recorded as works are progressing
--- old post above --- --- new post below ---

Goatboy said:
Whats going on with rail service between Newton Abbot and Plymouth? The FGW site implies it's open for trains but if you plan a journey on a Sunday it only offers buses. Is this an NRES error or are they not running trains on Sundays for some reason?

These are pre planned 27 hour possessions up until week 52 (March 25th) for other works

Zoe · 27 Feb 2014

MarkyT said:
There is a large brick built relay room for the signalling interlocking equipment together with a local power supply and a backup generator at the Exeter end of the station. This has an emergency operations panel within so an operator can be dispatched from Exeter to help manage local operations in the event of a control link failure. There is a similar smaller facility at Totnes, built at the same time in the mid 1980s. The latter site may have been switched to and left unattended in automatic 'through routes' which in that case would route everything through the platforms automatically. Emergency panels are not fully equipped signalboxes and typically don't have ancillary systems such as train describers, or a switchboard to answer signal telephones or radio systems, so the remote operator has to work in conjunction with the signaller for the appropriate area back at Exeter, being his hands and eyes effectively. The black signals at Dawlish Warren are a result of local power loss, not loss of the control link which would cause all controlled signals to return to their most restrictive aspect. Power may have tripped out during the incident but more likely the lineside 650v cables have been isolated for safety whilst heavy machinery and workers are busy given there is no requirement to run rail traffic except possibly engineering trains within the possession.

This is getting confusing, I asked about this on a signalling forum and was told (by someone who checked with Exeter panel) that there is no emergency panel at Newton Abbot and control has continued to be from Exeter.

carriageline · 27 Feb 2014

Zoe said:
This is getting confusing, I asked about this on a signalling forum and was told (by someone who checked with Exeter panel) that there is no emergency panel at Newton Abbot and control has continued to be from Exeter.

Take things you read on here with a mountain of salt!! Not saying this is incorrect or the case here, but 'some' enthusiasts state some very incorrect facts sometimes!

ECML180 · 27 Feb 2014

carriageline said:
Take things you read on here with a mountain of salt!! Not saying this is incorrect or the case here, but 'some' enthusiasts state some very incorrect facts sometimes!

Very true!

Anyway to confirm the facts, I work in signalling and there is an Emergency Panel at Newton Abbot. It's worked by fully trained beagles kept on standby at all times, occasionally a border collie fetches them tea. It's a very slick operation but sometimes you do get the odd dachshund coming around and causing trouble...

Now about that mountain of salt, might not be enough

455driver · 28 Feb 2014

Apparently the signal control information are being sent from Exeter to Penzance as Time Division Multiplex, from Penzance to Totnes as Frequency Division Multiplex (whatever the hell that is) to control the signals and it is working well (most of the time).

causton · 28 Feb 2014

Whereas further down the line, at the moment pigeons are specially trained to fly between signals and clear them to green as appropriate by pecking the appropriate aspect. The pigeons are not very fast, which is why sometimes trains feel really slow in Cornwall!

Rich McLean · 28 Feb 2014

455driver said:
Apparently the signal control information are being sent from Exeter to Penzance as Time Division Multiplex, from Penzance to Totnes as Frequency Division Multiplex (whatever the hell that is) to control the signals and it is working well (most of the time).

I would explain it in more detail, but fear many will not get their head around it. I had to learn that during trade training (Boring)

HowardGWR · 28 Feb 2014

Rich McLean said:
I would explain it in more detail, but fear many will not get their head around it. I had to learn that during trade training (Boring)

How true. I am interested in most railway subjects but as soon as it starts about signalling, my eyes glaze over and I start to fall asleep. Good job I never went for that as a career. Glad someone like you did.

najaB · 28 Feb 2014

HowardGWR said:
How true. I am interested in most railway subjects but as soon as it starts about signalling, my eyes glaze over and I start to fall asleep.

I'm the opposite - there's beauty to be found in every interlocking.

YorkshireBear · 28 Feb 2014

Its not that i don't find signalling interesting, i just don't understand it! Whereas the politic behind infrastructure provision in the UK i fully understand!

HSTEd · 28 Feb 2014

I prefer the pre SSI stuff myself, masses of relays just looks so much more impressive.

I like the later electromechanical telephone exchange assemblies for the same reason.

Dawlish sea wall collapse

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