Dawlish sea wall collapse

[MadCommuter]

As a civil engineer the viaduct thing seems like a risky idea that i wouldnt personally give any time to.

Indeed. Scour instantly springs to mind, notwithstanding what others have said regarding the land behind that needs protecting.

 

[YorkshireBear]

Indeed. Scour instantly springs to mind, notwithstanding what others have said regarding the land behind that needs protecting.

Yep, and also simply the lack of stability when huge waves hit. Bridges are not designed for that with the waves rebounding from the cliffs. Could be done but that would require extensive design and also some fairly deep foundations all adding precious time to the rebuilding. Better to have it as a wall and now pay for a bit more protection for the wall. Granite wave breakers aught to do the trick for 95% of situations.

 

[JohnB57]

One of the men up on the track is saying "wave" to the men on the footpath below.

And I imagine the one at the bottom is gesticulating something that could be mis-interpreted as "there's at least two months work here".

 

[Chris125]

Replacing the most vulnerable sections of stone sea wall with concrete better designed to deflect the waves along with slab track would seem a far more appropriate and cost effective answer.

Chris

 

[CalderRail]

Some good videos on BBC News here and here.

What's fascinating about the second clip is the demonstration of the sheer elastic strength of the steel.

 

[Ian Miller]

I personnaly dont think it looks as bad as it did in the earlier pictures.

Its also fairly obvious why it breached at that paticular point.

 

[Red Dragon]

I don't know if access from the beach is possible to bring materials in.

It may be possible to bring in rock protection at high tide in bottom dump barges and then send in D9's, back-hoes and Moxys at low tide to bring the rocks up the beach to form a first line of defence. I was involved in a similar operation along the North Wales coast.
This one is a difficult job because two faces need to be protected, the seaward to support and protect the railway, and the landward to support the properties and ground above the railway.
Unfortunately, the situation can't be fully assessed until the storms abate and a full inspection of the line, the condition of the adjacent properties, and any unsupported ground above the line can be carried out.
The rock protection could start fairly quickly to stave off the future onslaught of the waves, when there's a weather window which allows it.
It's a wonderful section of the UK's railway network.
Good old Isambard Kingdom B.

 

[daikilo]

At least NR have got there seen the damage so they know what they are dealing with that is the important thing. At low tide it sure looked calm!!!

As a civil engineer the viaduct thing seems like a risky idea that i wouldnt personally give any time to.

You may need to explain that, but having a large ammount of water on the inland side could be a threat not only to the line but the properties.

My personal opinion is that if the battering stops long enough and enough concrete can be shipped in, say 6 weeks is not ridiculous. What matters is to keep the rebuild as was brigade at bay. If they are let loose, a political and wider social disaster will occur.

 

[YorkshireBear]

Replacing the most vulnerable sections of stone sea wall with concrete better designed to deflect the waves along with slab track would seem a far more appropriate and cost effective answer.

Chris

I have been mulling over that all day. Having looked at the sea wall it is of very old design and as you say, not effectively designed to deflect waves. So in a way i agree with you, precast concrete sections, delivered to site by rail and craned in at low tides could be very effective. Slab track too, removes the need for any ballast whatsoever further potentially reducing the issues.

HOWEVER, concrete is not great at coastal conditions even when chemically altered to suit so i would suggest it more sensible to keep the ballast due to the pooling on slab track. The sea wall however should be okay. Granite boulders at bottom obviously to remove scour. I think it would be fairly important to keep the coastal path too.

 

[Busterfridge]

I've got a week booked for may 17th-24th touring cornwall/devon by rail, I think that has just been wrecked :cry::cry::cry:

 

[Rich McLean]

I've got a week booked for may 17th-24th touring cornwall/devon by rail, I think that has just been wrecked :cry::cry::cry:

It should be done by then, weather permitting. A rough guess is end of April/early May

 

[CallySleeper]

In answer to the question "how long is it going to take" Mr Hallgate's first words were "it's very difficult to say" before explaining that there needs to be a full structural assessment, then "off the top of our head it's 4-6 weeks" then again "it's too early to say"

So hardly a definitive timescale, and who can blame him.

I think having just said "it's very difficult to say" it was a bit idiotic to then pluck a figure out in the way he did. Especially when anxious Joe Public will be watching, wanting to find out how long trains will be disrupted for. There's probably now a number of people who truly believe it'll be open before April.

He should not have given into pressure and answered the question in the way he did, given his initial response.

 

[Red Dragon]

I've got a week booked for may 17th-24th touring cornwall/devon by rail, I think that has just been wrecked :cry::cry::cry:

Similarly, I was just about to book the sleeper to Penzance with some friends. Do a few days down there and have lunch in the FGW dining car on the way back to PAD on the final day.
The best laid plans of mice and men.......

 

[eastdyke]

I personnaly dont think it looks as bad as it did in the earlier pictures.

Its also fairly obvious why it breached at that paticular point.

I agree that it does not look as bad from this angle. The basic (lower level) sea wall appears to be intact.

I was absolutely amazed to see shots on BBC News showing that members of the public still have access to the sea wall walk, including the area with the suspended tracks!

That needs to be restricted, surely?

Perhaps, on the other hand, the shots were taken before NR/Emergency Services were substantially on site?

 

[LateThanNever]

Construction of breakwaters and any other palliative measures tends to be fraught with imponderables as far as effects elsewhere are concerned.

Coastal defence is a poorly-understood technology, it seems. I live within shouting distance of the North Devon coast between Westward Ho! and Appledore and all the 'expertise' spouted over the last few years about 'managed retreat' has proved to be total garbage. The coast here, in common with flood prevention elsewhere, has proved to be an absolute shambles when the mumbo-jumbo is designed to avoid spending money on prevention. Prevention which has been effective for years as long as modest spending on maintenance has been maintained.
It's rather like the poor effort on road maintenance with which many will be familiar.

One last point if I may - 'loose' means 'poorly fitting' and 'lose' equates to 'lost'.

I stand corrected - where are the courses in English as a foreign language?!
--- old post above --- --- new post below ---

I agree that it does not look as bad from this angle. The basic (lower level) sea wall appears to be intact.

I was absolutely amazed to see shots on BBC News showing that members of the public still have access to the sea wall walk, including the area with the suspended tracks!

That needs to be restricted, surely?

Perhaps, on the other hand, the shots were taken before NR/Emergency Services were substantially on site?

Pretty certain it's part of the South West Coastal Path so there is a right of way! Whether 'walkers' should be walking is another matter..

 

[Zoidberg]

I stand corrected - where are the courses in English as a foreign language?!
...

Please do not worry about that ... I am sure that most people, if not everyone who read your post, knew what you meant.

 

[amcluesent]

Chinese would have things repaired by Monday.

 

[Class83]

Which would take the sea about 10 minutes to rip apart, if you havent seen the sea in angry mode then you cannot comprehend the power of it!
--- old post above --- --- new post below ---

I meant to type a 5m high bank something like the link below, which are used to break up waves before they hit the main wall in a lot of places.

http://www.geograph.org.uk/photo/1579664

 

[Llanigraham]

I'm guessing that this must have been not long after the breech given the colour of the spray

I doubt it, looking at how far it had cut back to the landward when that photo was taken!

 

[Peter Mugridge]

Where is Eric Coates when you need him?!

 

[HSTEd]

Beach covering rock armour is probably a big no-no politically.

A breakwater offshore is probably the best bet really.
Does anyone know what the predominant wave movement direction is? Is it at an angle or straight out of the sea.

 

[transmanche]

Chinese would have things repaired by Monday.

The Japanese too. Just look how quickly they repaired a road after the March 2011 earthquake.

 

[cambsy]

Go to You Tube and type in Dawlish Seawall to see the storm and waves pounding the line, about 8 minutes worth, it shows the awesome power the storm unleashed and why so much damage done. Can someone put up links to the You Tube clips.

 

[DownSouth]

Just to bring a little prior experience to the issue of the timescale to rebuild the line, this incident in 2011 might be of a little interest. Rainfall caused by Tropical Cyclone Grant caused the Edith River rail bridge (in the northern part of the Adelaide-Darwin line used by The Ghan) to collapse when a train passed over (the locos rode suspended rails across, everything behind them was swept off the bridge or stopped before it) which took nine weeks to repair enough to resume limited-speed service.





One span of the bridge collapsed completely and the southern approach abutment had to be rebuilt. Even the cleanup of the rolling stock was a major job - notice the way intermodal spine cars were folded up like wet tortillas and this ex-DMU crew car (empty at the time, thankfully) was wrapped around a bridge pylon.



The reconstruction work involved was probably a bit simpler than Dawlish will be, but also a lot greater in magnitude to rebuild 350 metres of abutment and a bridge 11 metres above the river bed.


A different case here involved the Army blowing up a section of rail line to release floodwaters threatening a town! This one took about five weeks to rebuild but with a bridge in the gap where the embankment was previously.

 

[jopsuk]

As far as repairing it quickly goes, it is rather required that the weather calms down so they can even start. There's a relative lull today, though it'll still be wet and windy, followed by another deep storm this weekend. Whilst this weather pattern continues there's very little can be done, rather the damage will get worse.

 

[Haydn1971]

6 months hock::x Could be 12 or more. http://www.bbc.co.uk/news/uk-26042990

Can't quite see how extensive the damage is along the wall but it will need a coffer dam; new design of retaining wall to beat the weather and a major civil engineering job to complete. These jobs don't 'appen overnight.

Speaking as a civil engineer who's worked on many a highway scheme, plus as someone who's worked his life in a scream how high when asked to jump by politicians environment - I'd expect with all the flak going into Number 10 right now, the message coming across to Network Rail will be do whatever it takes to get the line reopened in weeks and worry about the cost of permanent repairs after the emergency fix is done - what's an emergency fix ? A load of aggregate dumped at sea in front of the damaged seawall to support a piling rig, protected by huge concrete sea defence boulders then a wall of piles into the area fronting the seawall, plus demolish the houses that have been undermined. I'd be interested to hear from any line engineers as to what the underlying material is in the area though - piling into rock isn't fun !

 

[crewmeal]

Bet you won't see the Enviroment Secretary in wellies down there.

 

[DXMachina]

Bet you won't see the Enviroment Secretary in wellies down there.

He doesnt believe in climate change. He'd probably turn up in swimshorts

 

[Johnuk123]

He doesnt believe in climate change. He'd probably turn up in swimshorts

Even the so-called experts have largely discounted the recent weather as being the result of climate change/global warming.

 

[jopsuk]

I'd be interested to hear from any line engineers as to what the underlying material is in the area though - piling into rock isn't fun !

I'm no geologist or engineer, but I'd take a punt on it being sandstone.