Washout at Dawlish

[The Stationmaster]

That's the system I mentioned in my post  #1505 above (click to link). They have it far more to the south than the Americans do. Because most of the strong winds are coming from the North West quadrant I'm not convinced that the coastal flooding potential will be significant for Dawlish. Other areas, yes, of course, along the north facing shoreline.

Still intelligent to keep a watching brief, always.

 

Best, Pete.

Agree - and what I mentioned in post 1502 (which Pete also quoted when providing his link), and here's the latest extended maritime forecast -

 

 

Niton From 1800 UTC Mon 03 Mar to 1800 UTC Thu 06 Mar

Complex trough of low pressure expected Iceland to Italy late Monday. Through Tuesday, Low Southeast Iceland 982 expected to move away north, and low southeast England 987, both filling, losing their identities. Low Hebrides 980, expected to move northeast, to Norwegian Basin 988 midday Tuesday, then away north. Meanwhile, ridge expected Fitzroy to Shannon early Tuesday, transferring east, declining. New low expected Shannon 990 midday Tuesday, tracking east-southeast, filling, losing its identity over western Channel early Wednesday. New low expected Bailey late Wednesday 970, Norwegian Basin 973 midday Thursday. Ridge builds Azores to southwest England Wednesday, to southern North Sea Thursday. Thames, Dover, Wight, strong winds developing Wednesday and Thursday. Irish Sea, occasional strong winds, moderating later Tuesday but further strong winds with occasional gales developing Wednesday and Thursday. Other areas, strong winds with occasional gales all areas late Monday and Tuesday, with risk severe gales at first Biscay. Occasional strong winds all areas Wednesday and Thursday

[DavidR]

Agree - and what I mentioned in post 1502 (which Pete also quoted when providing his link), and here's the latest extended maritime forecast -

 

 

Niton From 1800 UTC Mon 03 Mar to 1800 UTC Thu 06 Mar

Complex trough of low pressure expected Iceland to Italy late Monday. Through Tuesday, Low Southeast Iceland 982 expected to move away north, and low southeast England 987, both filling, losing their identities. Low Hebrides 980, expected to move northeast, to Norwegian Basin 988 midday Tuesday, then away north. Meanwhile, ridge expected Fitzroy to Shannon early Tuesday, transferring east, declining. New low expected Shannon 990 midday Tuesday, tracking east-southeast, filling, losing its identity over western Channel early Wednesday. New low expected Bailey late Wednesday 970, Norwegian Basin 973 midday Thursday. Ridge builds Azores to southwest England Wednesday, to southern North Sea Thursday. Thames, Dover, Wight, strong winds developing Wednesday and Thursday. Irish Sea, occasional strong winds, moderating later Tuesday but further strong winds with occasional gales developing Wednesday and Thursday. Other areas, strong winds with occasional gales all areas late Monday and Tuesday, with risk severe gales at first Biscay. Occasional strong winds all areas Wednesday and Thursday

Can we have this with music, please. 'Sailing away'?

[Captain Kernow]

It is simply due to the chemical characteristics and conductive potential of Sodium.

 

Basically in an ideal world you should get the same voltage at the finish or relay end of a track circuit as the voltage you put into it at the start or feed end. In reality of course you will get leakage through the rail fastenings, sleepers and ballast - however just how much will depend on things like the weather, how contaminated the ballast is, how effective the ballast is at draining away water, if the sleepers are timber, how much water they have absorbed. From a S&T perspective all these factors are summarised by the term Ballast resistance.

 

The lower the Ballast Resistance goes the lower is the voltage (or current to be precise - as thats what does the work) at the relay end of the track. If the relay end voltage gets too low the track circuit will become unstable, repeatedly flicking between occupied and clear with no train present and if it falls to low the track circuit will stay occupied.

 

Axle counters are of course unaffected by this - in fact Penzance has had them as a back up system for ages (given the unstable nature of the track circuits in stormy conditions) although in that instance the back up nature of the installation does limit capacity when they are switched in, but even they are no use when the track (and the signalling kit itself) gets completely submerged under floodwater.

 

As others have said it doesn't always have to be seawater that causes problems. For example road salt contaminating the track through level crossings is a well known problem (gritters should stop gritting over the crossing, but that doesn't help when vehicles naturally bring grit or salty slush onto the crossing from either side). Another example I know of is one winter the p-way engineers were having a problem with ballast freezing together in wagons and not coming out on an overnight job. To solve the problem someone applied a salt solution to the ballast - excellent idea you might think. Not so when the ballast was down and the track circuit resolutely refused to come clear. The S&T were apparently at a bit of a loss - everything they tried wasn't working, then somebody spotted something unusual about the ballast and to confirm their suspicions the went and actually licked a piece - which tasted salty! Apparently even after lots of jet washing it took about 6 months to a year before the rain naturally washed all the salt out of the ballast before the track circuit readings returned to normal and I believe there were still problems whenever the bit of track was tamped in subsequent years so eventually they had to bite the bullet and do a deep dig to get rid of it all and lay fresh non salty ballast.

Thanks Phil - eloquently put. It is essentially down to salt contamination and the fact that the track circuits don't work correctly (you can tell I'm not an Engineer, can't you?!   ). That means operations people like me have to institute Working by Pilotman over the single line section. Although we do have the axlecounter override section, it is unfortunately not the whole length of the single line, rather it covers the section closer to the station, which historically tends to get damp more often).

[phil-b259]

If anyone wishes to have a slightly more technical understanding of just how complicated a simple track circuit can be from an electrical point of view I recommend  you have a look at section 6 of this document

 

http://www.rgsonline.co.uk/Railway_Group_Standards/Control%20Command%20and%20Signalling/Codes%20of%20Practice/GKRC0752%20Iss%202.pdf

[rab]

Apologies if this has already been asked but it would be interesting to know how much concrete has been used to fill the hole???

[Dagworth]

If anyone wishes to have a slightly more technical understanding of just how complicated a simple track circuit can be from an electrical point of view I recommend  you have a look at section 6 of this document

 

http://www.rgsonline.co.uk/Railway_Group_Standards/Control%20Command%20and%20Signalling/Codes%20of%20Practice/GKRC0752%20Iss%202.pdf

Wet ballast glue on model railways can have exactly the same effect of track circuits refusing to clear... 

 

Andi

[yorkie_pudd]

Thanks Phil some great interesting reading in that document and a minor glimpse of PW signalling staff have got do etc.

[Geoff Endacott]

Apologies if this has already been asked but it would be interesting to know how much concrete has been used to fill the hole???

 

Lots.

 

Geoff Endacott

[Gwiwer]

Apologies if this has already been asked but it would be interesting to know how much concrete has been used to fill the hole???

 

May I also refer interested parties to this link?  

 

https://www.facebook.com/pages/Shitload-is-a-Standardized-Unit-of-Measurement/273501336010068?fref=ts

 

[Coombe Barton]

Calculate

 

100m washout

5m (say) wide

3m (say) deep

 

= 1500 cubic metres

 

Density of concrete 2,400 kg/cubic metre

 

Say 3,600 tonnes

 

This is an approximation.

 

I'd rather go with Gwiver's definition.

Edited March 3, 2014 by Coombe Barton

[Captain Kernow]

Say 3,600 tonnes

 

 I'd actually heard slightly more than that figure, but should be able to find out later on.

[Coombe Barton]

I'd actually heard slightly more than that figure, but should be able to find out later on.

I'll still go with Gwiver's figure

 

My calculation is based on a load of estimates, but it's interesting that it's in the right region.

 

As an aside someone tried to stem an active lava flow threatening a village by dropping concrete blocks into it - they floated away. As quoted the density of concrete is about 2,400 kg/cu m but basalt is 2,800 - 3,000 kg/cu m, so would float. Very big helicopter waste of time. Think it was in Italy.

[TrevorP1]

I'll still go with Gwiver's figure

 

My calculation is based on a load of estimates, but it's interesting that it's in the right region.

 

As an aside someone tried to stem an active lava flow threatening a village by dropping concrete blocks into it - they floated away. As quoted the density of concrete is about 2,400 kg/cu m but basalt is 2,800 - 3,000 kg/cu m, so would float. Very big helicopter waste of time. Think it was in Italy.

So, ideal material to repair the sea wall would be lava blocks then... Sorry...

 

Trevor

[Fat Controller]

So, ideal material to repair the sea wall would be lava blocks then... Sorry...

 

Trevor

You may scoff..

Quite a bit of the sea-wall between Llanelli and Burry Port, along with much of the breakwater and outer harbour walls at Burry Port, is made of large chunks of man-made lava; slag from the local steelworks and copper-works. Part of the wall at Burry Port is made using old barges, filled with still-molten slag, which was then allowed to harden.

[RedgateModels]

are they casting the walls now?

 

[lmsforever]

How long before the ballast goes down?

[Pete Harvey]

Captain

 

Could you please find out if what the team has done is a case of implementing the long term solution for Dawlish several year ahead of scheduled of is what they have done a completely emergency measure to repair the track that was damaged in the storm?

 

I ask this as it would surprise me if there has not been a plan in the making for several year waiting for the right opportunity, just in case the inevitable happens as it did last month.

 

Pete     

[surfsup]

Captain & Others on the project,

 

Just to show your efforts are well appreciated by those not just on here, a page appears to have been set up on Facebook by those local to Dawlish.  

 

https://www.facebook.com/dawlishorangearmy

[Pete 75C]

Captain & Others on the project,

Just to show your efforts are well appreciated by those not just on here, a page appears to have been set up on Facebook by those local to Dawlish.  

https://www.facebook.com/dawlishorangearmy

 

Whoever set that up, that's a really nice thought. If you have a Facebook account, I think you need to log in to be able to read all of the comments from local residents and others. Please do, it's worth it. I particularly like the comment from the lady who's been watching the NR guys from her living room window each day. She says it's better than TV but then she couldn't watch TV even if she wanted to because she lost her aerial in the storm...

Edited March 3, 2014 by Pete_S

[TrevorP1]

You may scoff..

Quite a bit of the sea-wall between Llanelli and Burry Port, along with much of the breakwater and outer harbour walls at Burry Port, is made of large chunks of man-made lava; slag from the local steelworks and copper-works. Part of the wall at Burry Port is made using old barges, filled with still-molten slag, which was then allowed to harden.

 

Appreciate this is OT but on the subject of employing waste materials I understand that, way back when,  some lines on the Isle of Man were ballasted with mining waste containing lead - apparently they didnt have much trouble with weeds...

 

Cheers, Trevor.

[RJS1977]

Appreciate this is OT but on the subject of employing waste materials I understand that, way back when,  some lines on the Isle of Man were ballasted with mining waste containing lead - apparently they didnt have much trouble with weeds...

 

Cheers, Trevor.

 

Which inspired the opening of the "Small Railway" on the Isle of Sodor to collect the waste....

[Coombe Barton]

The cast blocks of slag are called scoria. However, they, like solidified lava, have loads of air bubbles exsolved as the lava/slag cools, and are not suitable to long term defenses as their bulk density is too low. (think opening a lemonade bottle and freezing it as it opens) And, because of the high proportion of iron, oxidise readily and decompose. They can be used for docks where the wave action is limited, but I don't think coastal; defenses are their forte. There's a lot of walls and some small buildings around Hayle built from scoria.

 

If you use solid rock of the basalt/ gabbro type - the stuff that's cooled deep and does not have the bubbles then it's incredibly hard to cut into blocks. It would be OK as rip-rap, but you'd have to be searching for a long time in a pile of rocks to find anything that would readily build. It has high friction which is why the aggregate is used for road surfaces.

 

[EDIT] The most convenient gabbro quarry for RipRap is at Porthustock - direct sea access. They do big lumps as well as small lumps. Trouble is to get it to Dawlish you'd have to have a spell of calm weather to float the boat (barge) close enough in to be offloaded.

Edited March 3, 2014 by Coombe Barton

[Coombe Barton]

And if you can't get onto Facebook - this is a YouTube video tribute - it's linked from the tribute site.

 

[Andy W]

Appreciate this is OT but on the subject of employing waste materials I understand that, way back when,  some lines on the Isle of Man were ballasted with mining waste containing lead - apparently they didnt have much trouble with weeds...

 

Cheers, Trevor.

And then in 1964/65 when Douglas Gasworks closed a lot of the waste was used to reballast the Port Erin line. It was blue in colour, and no weeds grew anywhere near it. I often wonder what side effects it may have had on the P-way staff.

[New Haven Neil]

None, if they are from Foxdale.

 

local joke, sorry.