Weather disruption caused in 2014, and how to prevent it happening again - ongoing discussion

[whole diary]

[Pb_devon]

The lobstervision webcam is now showing the first few 'L-shaped' precast wall sections being fitted, from about 1530 onwards on 6th March.   I presume the sections are fastened with some sort of drilled fixing into the lower level of concrete block work that forms the seaward facing side?

https://www.lobstervision.tv/home

username and password = "dawlish"

Paul

...or more concrete poured behind and over the foot of the pcc sections.  I can see this being the only section left when all the rest of the sea wall has succombed to the ravages of the sea - it's so massively over-engineered! (note: I am of course not predicted the end of the line here  )

[paul7575]

I also caught a piece of info, in one of the many reports on the repairs, that suggested that some of the wall sections away from the main breach are to be cast in situ concrete, with the formwork on the seaward side including fibreglass mouldings (from a firm in Plymouth) to simulate a stonework effect.

I guess that would be painted afterwards, or would they colour the concrete?

Paul

[JayMac]

Just happened to be watching the new Dawlish webcam (1752 07/03/2014) when I heard the 'crunch, crunch, crunch' of approaching footsteps on ballast.

A lone hi-vis clad bod came into view, walking ahead of a RRV^▸ (Road Rail Vehicle) loaded with pre-cast concrete sections for the damaged sea wall section, and towing other, no doubt important, bits and bobs.:

[JayMac]

Further to my previous post, and with some technical jiggery-pokery, here's a video of that RRV^▸ (Road Rail Vehicle) making its way to the worksite:

http://www.youtube.com/watch?v=7a5YtTJwbYI

[bobm]

With the planned re-opening at Dawlish, FGW^▸ (First Great Western) have announced they plan to re-start the Night Riviera sleeper service on Wednesday 9th April.

Details, plus updated news on availability of other advance tickets, see http://www.firstgreatwestern.info/coffeeshop/index.php?topic=13628.0

[Pb_devon]

Thanks bnm.
Slightly alarmed that the RRV^▸ (Road Rail Vehicle) driver cannot see the banksman due to the PCC^▸ (Police and Crime Commissioner) sections in front of the unit!!

[SandTEngineer]

Taunton to Bridgwater to reopen on Monday 10 March 2014 as stated on the WNXX^▸ (Stored Unserviceable, Mainline Locos HQ All Classes) forum:

Fordgate reopens Monday with a 30 ESR^▸ (Emergency Speed Restriction ) maybe lifted to 50 ESR on Thursday
Talking by one on the Down and TBW^▸ (Temporary Block Working) on the Up
Talking of long section axle counters in two weeks pending longer term resignalling to fully restore the route

[stuving]

The lobstervision webcam is now showing the first few 'L-shaped' precast wall sections being fitted, from about 1530 onwards on 6th March.   I presume the sections are fastened with some sort of drilled fixing into the lower level of concrete block work that forms the seaward facing side?

https://www.lobstervision.tv/home

username and password = "dawlish"

Paul

...or more concrete poured behind and over the foot of the pcc sections.  I can see this being the only section left when all the rest of the sea wall has succombed to the ravages of the sea - it's so massively over-engineered! (note: I am of course not predicted the end of the line here  )

Last night they placed the rest of the sections and drilled down through the holes, and this morning they were inserting some kind of stud through steel plates in the recesses round the holes. The drilling was a wet process, e.g. a diamond core drill, and I can't see what's holding the studs in - probably resin, as squirting that in should be pretty quick.

I don't agree it's massively strong, though probably still better than the masonry wall was. Those L-sections, despite being reinforced concrete, are not very thick.  And the face of the concrete below it is just recycled blocks not tied to each other or the concrete fill. Fine to provide mass behind a wall, but I'd expect a foot or so of reinforced concrete to form a real seawall.

This work was done for speed, and it has the merit of being self-supporting and strong enough for most weather. How one would uprate other stretches is less clear. If you want to take out the masonry wall and replace it with something tougher, you need to hold the fill in place somehow.

Of course you have to take a view on how likely another storm this bad - or worse - is going to be, before you decide how much extra strength to provide.

[ironstone11]

I don't agree it's massively strong, though probably still better than the masonry wall was. Those L-sections, despite being reinforced concrete, are not very thick.  And the face of the concrete below it is just recycled blocks not tied to each other or the concrete fill. Fine to provide mass behind a wall, but I'd expect a foot or so of reinforced concrete to form a real seawall.

My observation was that all the rows of recycled blocks are tied into the bulk concrete with one or two sizeable rods per block with a square plate embedded in the concrete. The top layer of concrete, where the recycled blocks are on their sides has the added benefit of being reinforced in addition to the tie rods.

I don't think the top part of the L pieces is really classsed as sea wall. It is more to contain the track ballast and provide safety for track workers. The sea wall  I suspect will be rebuilt as per the original, if mainly for cosmetic purposes. All the new concreting and L pieces have been placed inside the line of the original wall with the aim of getting the railway running again as quickly as possible and so as not to interfere with the outer wall rebuilding.

I do wonder why the L pieces are shuttered along the landward edge. I supect that the seaward side is also shuttered as a scaffold walkway has been constructed for access. Are the narrow gaps to the sides and undersides to be filled with something?  They seem rather small gaps for normal concrete to fill.

What does surprise me is where does the water that comes over the wall go? I know there are what appear to be drains down the centre of the concrete pad, but where do they go? To a soakaway I suspect, which probably won't allow much flow. Surely there is a possibilty of the new section forming an effective concrete lined water channel.  I would have though that some apertures in the wall fitted with flap valves to let the water out might have been a good idea.

 

[paul7575]

My observation was that all the rows of recycled blocks are tied into the bulk concrete with one or two sizeable rods per block with a square plate embedded in the concrete. The top layer of concrete, where the recycled blocks are on their sides has the added benefit of being reinforced in addition to the tie rods.

Don't those blocks being used as formwork also have a relatively shallow 'tongue and groove' type interlocking at the ends?   It just occurred to me that there are very similar if not identical blocks being used as a vehicle barrier outside the gates of the closed Ford factory in Swaythling - I'll have a closer look next time I go past...

Paul

[ellendune]

My observation was that all the rows of recycled blocks are tied into the bulk concrete with one or two sizeable rods per block with a square plate embedded in the concrete. The top layer of concrete, where the recycled blocks are on their sides has the added benefit of being reinforced in addition to the tie rods.

Don't those blocks being used as formwork also have a relatively shallow 'tongue and groove' type interlocking at the ends?   It just occurred to me that there are very similar if not identical blocks being used as a vehicle barrier outside the gates of the closed Ford factory in Swaythling - I'll have a closer look next time I go past...

Paul

If they are the same that would probably mean that they are a standard product - making it much easier to get hold of a large number of them in a hurry!

[paul7575]

If they are the same that would probably mean that they are a standard product - making it much easier to get hold of a large number of them in a hurry!

This looks like them:  http://www.uniqwin.co.uk/safety_security_barriers/locking_concrete_blocks.html

They must do them on sale or return - I don't think the Dawlish ones will re-surface for a few years...   

Paul

[paul7575]

The March online edition of the Rail Engineer magazine has an article on the Dawlish repairs, (interesting in itself), but luckily there's also an advertising page (for TRS road rail vehicles) immediately before the article on page 11.  This gives a good view from the very east end of the damage site which is useful in that it highlights the different heights of the trackbed and the container barrier, (I find the webcam view doesn't make the relative heights clear). It also suggests that the concrete blocks are being laid well within the existing stone wall - at least at the location the photo is taken from.

This does support the suggestion in ironstone11's post above that the 'L-shaped' sections will be inboard of the repaired wall...

http://www.therailengineer.com/print-archive/

(Its also a good read on electrification issues this month...)

Paul

[ironstone11]

Don't those blocks being used as formwork also have a relatively shallow 'tongue and groove' type interlocking at the ends?   It just occurred to me that there are very similar if not identical blocks being used as a vehicle barrier ...

Yes, they are the standard interlocking type and very obviously second hand. As Paul states they are often found blocking off gateways and entrances to work sites. Some have quite a bit of paint on them, although the ones used in the outer wall have been more or less free of paint.

Interestingly they don't seem to be using the outer (sea side) pair of holes on the L shaped pieces. Structurally these are the better ones to use assuming most of the pressure comes from the sea. I wonder if they found the blocks too hard to drill? Probably very hard and with lots of reinforcing.

A large cube shaped 'tub' is visible on site about the footprint of a pallet. Suspect this may contain the resin used for securing the pins or studs. On second thoughts probably not, as the resin would be in two parts. It's more likely just water for cooling the drills.





 

[stuving]

The March online edition of the Rail Engineer magazine has an article on the Dawlish repairs, (interesting in itself), but luckily there's also an advertising page (for TRS road rail vehicles) immediately before the article on page 11.  This gives a good view from the very east end of the damage site which is useful in that it highlights the different heights of the trackbed and the container barrier, (I find the webcam view doesn't make the relative heights clear). It also suggests that the concrete blocks are being laid well within the existing stone wall - at least at the location the photo is taken from.

The section in the foreground of that picture isn't one we've seen before. It looks as if part of the wall and fill has been washed away, but one line (with its support) survives. Blocks have been used to fill the gap, two or more deep - how the remaining fill has been managed isn't visible. A very different style of repair, and looking more like a temporary fix.

The main rebuild is not quite as the article describes - for a start the blocks are a different shape. I only ever saw one tie-bar per block from the outer to the inner wall - diameter unknown. It took it as there to hold them in place during the pour, and I never saw any other steel ties going into the wall (which is not to say there weren't any).

Yes, they are the standard interlocking type and very obviously second hand. As Paul states they are often found blocking off gateways and entrances to work sites. Some have quite a bit of paint on them, although the ones used in the outer wall have been more or less free of paint.

Interestingly they don't seem to be using the outer (sea side) pair of holes on the L shaped pieces. Structurally these are the better ones to use assuming most of the pressure comes from the sea. I wonder if they found the blocks too hard to drill? Probably very hard and with lots of reinforcing.

Interlocking? They have a groove all round them, but you'd need to put a key in to provide any location, and that's not going to be at all strong.

Which fixings do most to hold the L-sections depends on what load they are there to resist. If they are to hold the ballast and track, the inner ones are fine.

So does that mean they are not meant to take loading from the sea side? And would fixing one to the top block really help, if it's not fixed to the one below? I suspect the holes fall close to the inner edge of the blocks, which would make drilling them a bad idea, rather than their being too hard. New concrete may be softer, but if you are using a cutting technique that's not likely to help (it might even make it trickier).