Ballast

murphaph

just curious,
Why does the ballast sometimes completely cover the sleepers and other times it doesn't?

Here in Germany it pretty much never covers the sleepers and always looks really "neat" with a well defined "shoulder" of ballast usually being present.

In Ireland it seems to be a mixture, with often no well defined shoulder of ballast to be seen. Is the a technical reason for the differences?

Hungerford

murphaph wrote: »

just curious,
Why does the ballast sometimes completely cover the sleepers and other times it doesn't?

The ballast compresses over time due to the weight of the trains on the rails above. Hence its levels fall over time.

Cookie_Monster

the Germans probably pay someone to keep it tidy when there's really no need at all

murphaph

Cookie_Monster wrote: »

the Germans probably pay someone to keep it tidy when there's really no need at all

A mate of mine here is and engineer and he worked for Network Rail for a few years. He told me "there's nothing permanent about the permanent way"...ie, it's constantly shifting and needs to be maintained carefully.

I see images of newly laid stretches in Ireland (the WRC for example) and the ballast is already covering the sleepers. Is it a simple matter of them using too much?

Another question about ballast:
Do Irish Rail use different ballast on under-bridges. In Berlin at any rate it is clear that they use a fine grain ballast and usually wooden sleepers on sections of track being carried by a bridge. Does this ballast allow less or more movement?

Why would they use wooden sleepers (in the middle of concrete ones) for a bridge? I can understand it with points that it's a more flexible material to work with but on a bridge? Is it just because it's easier to install check rails?

Cookie_Monster

wood would absorb the vibrations better than concrete, transmitting less to the bridge structure? this wouldn't normally be an issue on solid ground so stronger concrete is used...

(I'm guessing)

Losty Dublin

A mate of mine works PW for a contractor on Irish Rail tracks. According to him, concrete is covered by ballast as it doesn't deteriorate unlike timber and thus it lasts longer; it also stops it sinking or moving as readily so it has an anchoring role. Once it's tamped fully, it can cope with higher speed trains to boot.

dowlingm

this link (PDF) talks about composite sleepers but includes some discussion of the issues around bridge sleepers

steamengine

murphaph wrote: »

just curious,
Why does the ballast sometimes completely cover the sleepers and other times it doesn't?

Here in Germany it pretty much never covers the sleepers and always looks really "neat" with a well defined "shoulder" of ballast usually being present.

In Ireland it seems to be a mixture, with often no well defined shoulder of ballast to be seen. Is the a technical reason for the differences?

This YouTube video shows a tamping machine in action and how the track is lifted by a set of guide wheels before the tamping action takes place. The 'tines' or vibrating levers then pack the ballast directly under the sleepers. It would appear that generally speaking the overall ballast level will drop relative to the track whenever the tamping process takes place.

https://www.youtube.com/watch?v=HTEG8_2_1g4

Victor

If you dig soil out of the ground and put it in a truck, the volume may increase by 50%, as it is now loose and has large numbers of air pockets.

In reverse, if you lay ballast, it starts with a large number of air pockets and the vibration from the construction equipment and the passing trains makes it gradually settle. Hence extra speed restrictions on new track. While the sleepers may be covered at the start, they might not be after a period of time until more ballast is added.

Wet ballast will tend to settle differently to dry ballast. The adding of sand may have been done to minimise settlement.

steamengine

Victor wrote: »

If you dig soil out of the ground and put it in a truck, the volume may increase by 50%, as it is now loose and has large numbers of air pockets.

In reverse, if you lay ballast, it starts with a large number of air pockets and the vibration from the construction equipment and the passing trains makes it gradually settle. Hence extra speed restrictions on new track. While the sleepers may be covered at the start, they might not be after a period of time until more ballast is added.

Wet ballast will tend to settle differently to dry ballast. The adding of sand may have been done to minimise settlement.

+1 .......Our photo thread incidentally has pics of settled and unsettled ballast. The size and shape of the stones are important, generally rough with sharp edges and 'flat' surfaces so they all interlock eventually on settlement.

corktina

Ballast covering the slepers is an Irish oddity. It isnt general practise on most railways.

murphaph

corktina wrote: »

Ballast covering the slepers is an Irish oddity. It isnt general practise on most railways.

This would be my take on it too. I wonder why...

foggy_lad

murphaph wrote: »

This would be my take on it too. I wonder why...

Posssibly a feature on older lines to cover rotting sleepers from view? or just putting plenty of ballast out initially so the line wont leen extra ballast for longer?

Captain Chaos

Speaking of rotting sleepers, take a look at the wooden sleepers all along platform 5 at Connolly. There are some major cracks gone almost right through them. I just happened to be looking at them while waiting for a train the other day and was shocked at the condition they were in.

Jehuty42

Captain Chaos wrote: »

Speaking of rotting sleepers, take a look at the wooden sleepers all along platform 5 at Connolly. There are some major cracks gone almost right through them. I just happened to be looking at them while waiting for a train the other day and was shocked at the condition they were in.

There's some major engineering works(with line closures) over the next month or so, maybe something will be done then.

John R

foggy_lad wrote: »

Posssibly a feature on older lines to cover rotting sleepers from view?

Every other post you make on this board contains some sort of unsubstantiated accusation of wrongdoing, provide some evidence for your various accusations or just stop doing it.

Captain Chaos wrote: »

Speaking of rotting sleepers, take a look at the wooden sleepers all along platform 5 at Connolly. There are some major cracks gone almost right through them. I just happened to be looking at them while waiting for a train the other day and was shocked at the condition they were in.

Track in major stations like Connolly is generally left alone for much longer than on general running lines.

The extra complexity of the pointwork, signalling and platform alignment makes it a much bigger job to replace than plain track.

It is also not necessary to replace as often because despite the heavy use those lines get the very low speeds mean far less forces are acting on them and they will remain safe to use long after all other track of a similar vintage has been replaced.