Great Western Coffee Shop

(http://www.wellho.net/pix/fencedoff.jpg)

The picture shows the track alongside the disused section of the platform at Melksham on Saturday. It looked a bit odd even from the section in use, so I got as close as I legally could to get a better look, and was sufficiently concerned to give Network Rail a call.  It seems they weren't aware of any problem, and took the report seriously ... but I got no feedback as to whether or not there was indeed a problem (and my report was a valid and useful one) or whether track can look like this and be normal / have the problems picked up at routine inspection.

I felt a bit "damned if I call, damned if I don't".  To help me in the very unlikely event of finding anything like this in the future, can our experts here tell me if this track is in what they would consider safe condition (so I called un-necessarily), or if I was correct to call.   Note - I do not wear a red petticoat, so don't have the equipment to stop trains myself  ;)

IMHO it depends on what the permitted speed is.
Such poor condition track would be potentialy dangerous at a high line speed, but little cause for concern at very low speed, as in some platforms.

It appear that the ballast has either disintegrated, or been driven downwards into the underlying soil.
This results in excessive movement of the sleepers and rails as trains pass, this gets worse as time passes since the continual movement wears away or displaces more ballast, and tends to pollute the ballast with mud/soil.
In time a broken rail can result, or the track becomes so distorted that derailment occurs.

De-railment at 100 MPH can result in a destructive accident with substantial loss of life, at very low speed the result is far less serious.

IMHO you acted correctly in reporting this, network rail will know the permitted speed, and can therefore decide if the matter is urgent, or can wait until the next routine visit.

I think you were correct to call. I suspect that it's just a case of a 'wet bed' as it's known and will need remedial attention sometime soon, but not urgently as sleepers and fixings are all in place. It will deteriorate over time and if it gets too bad a driver will report it as a 'bump' - in fact it might be work in progress anyway as it looks like some support sleepers may have been inserted? But any time a passenger notices something amiss it's worth reporting on a 'just in case' basis.

It is called a 'wet bed'.

It occurs due to 'voiding' when the ballast underneath a sleeper settles or is eroded and thus is no longer providing vertical support to the sleeper.

At this stage if the draininage is not good, water will tend to lie in the ballast and with the attition of concrete sleepers against the ballast, you get the white slurry, which is predominantly powdered concrete.

The clogging of the ballast with concrete dust will itself then cause damage to the adjoining ballast and will breakdown the natural drainage.

Nothing too serious, but not a desirable conditon for track to be in. It will probably be sorted when the area is patrolled again.

Sorry II, it seeems we posted replies at the same time!  ;D

Did it appear overnight or should it have been noticed before?

Interesting it's a "wet patch". For many years there was a wet patch on the Up Relief at Slough just opposite the Down end of Platform 4 it was most interesting watching the stone hoppers pushing the sleepers up and down and the wagons rocking.

I think it's been cured but it was there for long time.

Gosh - good question.  It was my first visit to the station for a week, and looking back at a picture that I took on the previous Sunday (used in this document (http://www.savethetrain.org.uk/keynote_2010.html) - first photo) it looks like 2 or 3 sleepers were 'wrong' then, versus 10 or so a week later.

The line is not fast (50 m.p.h?) as it's quite close to a corner; a certain amount of freight, and the occasional stopping passenger train, but almost exclusively in the dark at this time of year. However, it's frequently used as a diversion route for HSTs and is on several of the 16 routes the sleeper train sometimes takes!

so you might have spotted before a NR routine inspection did (which I assume would only be every few weeks on that line at the most?) - in which case you reporting it was especially valuable.

platform 1 at westbury looks like that aswell

No problem, Sprog. Your reply certainly had the technical edge on mine!  :)

There's a very bumpy section of track just west of Bath Spa on the down line.  I notice it every trip. It does worry me that it's so noticeable, though fortunately speed is still faily low at that point.

There used to be a very bumpy bit of track between Topsham and the M5 bridge on the Exmouth branch. Lurching over it on a 158 was bad enough: I shudder to think what it was like on a Pacer. I think it's been replaced now. Another bouncy bit that may still be there is on the up line i.e. Exeter-bound, just west of Teignmouth. I think it's on the crossover line used when the down line on the sea wall is out of bounds - you'll know when you pass over it!

Taunton to Castle Cary on a full line speed HST whilst stood in the buffet car is quite worrying ::)

Also on a HST on the down line between Durham and Darlington at full line speed, bouncy enough to make me want to get off the train, which is rare  ::) :P ;D

Wet beds occur all over the place, they can be caused by various underground faults a void opening, unnoticed slow land movment, often poor drainage. But what starts as one or two sleepers "pumping" can soon spread and are a bit like Cancer as the bigger they get the FASTER the problem spreads.
In simple terms where "pumping" is occuring the sleepers no longer surport the Rails and this causes Extra pressure on the adjacent sleepers where due to the effect of "pumping" ballast is being washed out or ground down.

It's very much like putting a Weight on a Ruler across two books and slowly moving the books away from each other, the "Pumping" Gets worse in the middle having a Snowball effect.

They can be simple to cure OR a right B*****D, when NR have repaired this track it will be worth keeping an eye open for it occuring again, because IF the cause ISN'T sorted it will happen again.

As a driver I can confirm that the main lines between Bristol and London are riddled with wet beds. Some big Some small. Not very often is it needed to impose speed restrictions even if the line speed is 125. From a passenger point of view, ever noticed a bit of a bang from the wheels when hurtling along? This is caused by a train going over a wet bed!

out of our area there is a big one on the line between romley and marple

To complete the story, here's a "two weeks later" picture.

(http://www.wellho.net/pix/drybed.jpg)

Interesting - thanks.  The extra sleepers were presumably just a temporary measure.   Looks like the line is now ready for an intensive passenger service  ;)

At least it's not a problem like this ;D

See 5:49 in the video below :)

http://www.youtube.com/watch?v=mkaINEKwW2Y&feature=related

 you know i was going to post this but couldnt remember which one it was