Help needed with stability of embankments

[Lumberjack84]

Hi,

I am new to the forum and have heard nothing but good things from my fellow students.
I am currently studying at Newcastle college rail academy, attending a level 3 course in rail engineering. As part of my p-way assignment one of the tasks is becoming very difficult to find information on which is :
Effect of severe weather on stability of embankments, which has three sections- severe hot weather, server cold/ice weather and severe rain weather.
Effect on embankment and precautions is what's needed on the three.

So I was wondering if anyone has any information on the issue or could possibly direct me to the correct place, it would be greatly appreciated.

 

[swt_passenger]

Hi,

So I was wondering if anyone has any information on the issue or could possibly direct me to the correct place, it would be greatly appreciated.

One avenue that might get you going is to look at a few accident reports. This one below will include various cross-references, and is a report the Rail Accident Investigation Branch did a few years ago after a number of landslips in quick succession:

https://assets.publishing.service.gov.uk/media/547c8fc4e5274a428d000147/R082014_140402_Landslips.pdf

There are other reports into discrete single failures, which will be on their website somewhere, I'd suggest searching on landslips, cuttings, embankments etc and see what comes up. A few are listed towards the end of the above report.

From what I've read over the years, a number of incidents have been due to failure of drainage of one sort or another - and sometimes the drainage is outside the NR boundary, so out of sight, out of mind...

 

[Lumberjack84]

Good morning,

Thank you for getting Intouch.

I feel half the battle I've had is not knowing where to look and what I'm actually looking for, which in a sense seems daft.

That's great I will go down the avenues provided and hopefully gain knowledge to what I'm hoping to achieve

Thanks so much so for help

 

[YorkshireBear]

Hello,

Through your college do you have any access to papers and online recorded presentations from the institution of Civil Engineers? Or journals such as Rail Engineer?

There have been some good recent papers on earthworks and climate change.

Other links to John Dora consulting a very important consultancy on this subject.

http://www.nerc.ac.uk/research/partnerships/ride/lwec/report-cards/infrastructure-source01/

Also have you seen the Network Rail Route Weather and Climate Change adaptation plans. They have some useful information in them too.

That is just a starter for now.

 

[telstarbox]

More generally, a geotechnics textbook might help your understanding - the core text on my uni course was "Soil Mechanics" by William Powrie.

 

[Quakkerillo]

You don't specifically have to look for railway-related, as any sloped surface has stability related to it.

Just look for slope stability, and follow up from there, and you should be able to find quite some information. An embankment is in a way just a slope that has a sort of 'roof'.

 

[Ploughman]

A couple of related incidents.
http://www.gwsr.com/enthusiasts/History/Then_and_now_-_Chicken_Curve.html

https://www.gov.uk/government/news/report-032017-trains-passed-over-washed-out-track-at-baildon

 

[civ-eng-jim]

If you do a search for "The effects of climate change on slope stability" articles will capture extreme droughts and extreme rainfall events.

Extreme cold isn't something I've ever really thought about affecting slope stability. It would have to be extremely cold for a long period of time before the ground freezes deep into a slope/embankment.

 

[The Ham]

If you do a search for "The effects of climate change on slope stability" articles will capture extreme droughts and extreme rainfall events.

Extreme cold isn't something I've ever really thought about affecting slope stability. It would have to be extremely cold for a long period of time before the ground freezes deep into a slope/embankment.

Me neither, in road design the assumption is that as long as the material isn't frost susceptible within 450mm of the surface then there shouldn't be a problem.

However, as others have suggested, water can be a major problem. As such good subsoil drainage is key.

 

[dviner]

If you do a search for "The effects of climate change on slope stability" articles will capture extreme droughts and extreme rainfall events.

Extreme cold isn't something I've ever really thought about affecting slope stability. It would have to be extremely cold for a long period of time before the ground freezes deep into a slope/embankment.

(no civil engineering experience here, so forgive me if the answer is obvious)

If the embankment face is topsoil, wouldn't a freeze/thaw cycle, combined with the slope of the embankment make it more likely that the first few millimetres would be prone to loosening and slippage, leading to a gradual erosion?

 

[Trog]

(no civil engineering experience here, so forgive me if the answer is obvious)

If the embankment face is topsoil, wouldn't a freeze/thaw cycle, combined with the slope of the embankment make it more likely that the first few millimetres would be prone to loosening and slippage, leading to a gradual erosion?

Not if you use a sophisticated bio mechanical soil retaining system such as grass.

I think freezing is only likely to be an embankment problem, if your climate is cold enough that the embankment becomes deeply frozen, and stays that way for long enough for ice lenses etc. to build up. These can cause the ground to heave, then in the spring they melt leaving a void, causing settlement or collapse.

 

[The Ham]

Not if you use a sophisticated bio mechanical soil retaining system such as grass.

I think freezing is only likely to be an embankment problem, if your climate is cold enough that the embankment becomes deeply frozen, and stays that way for long enough for ice lenses etc. to build up. These can cause the ground to heave, then in the spring they melt leaving a void, causing settlement or collapse.

Freezing tends to be more of a problem the more moisture there is, as such an slope should be relatively fine as there would be limited water content in it.

 

[dviner]

Not if you use a sophisticated bio mechanical soil retaining system such as grass.

Sounds a bit complicated. Could be an expensive investment...

I think freezing is only likely to be an embankment problem, if your climate is cold enough that the embankment becomes deeply frozen, and stays that way for long enough for ice lenses etc. to build up. These can cause the ground to heave, then in the spring they melt leaving a void, causing settlement or collapse.

The OP did mention severe weather conditions.

Ice lenses - never heard that term before. Amazing the stuff you can pick up reading the forum.

 

[D Foster]

Hi,
Effect on embankment and precautions is what's needed on the three.

The main "precaution" with all civil works is routine inspection. Sounds ridiculously simple - but - cutting back on monitoring is not a cost effective solution to shortage of funds - the results can be far more expensive.
Old fashioned inspection was achieved by local gangs that knew their patch walking their lengths - and knowing how things should look - where the troublesome patches were. Modern monitoring includes all sorts of hi-tech stuff. Whether this can be as good as the mark 1 eyeball is a moot point - especially when it comes to spotting details like a drain blocked by the efforts of a burrowing bunny or badger. Tree roots and leaf fall are additional issues.
A more remote precaution employed is following the weather forecast. In my experience in chalk land extreme rain and/or frost brought out additional chalk fall patrols - a combination of heavy rain (or snow melt) and severe frost can bring down a lot of chalk... So - one thing to consider "precaution wise" is the local geology... You will get enormously varying effects between clays, sands and hard rocks - for starters... So one "precaution" in the modern world is to have a database of everything the structures are built on or through. Knowledge of what is out there on the ground is essential - far more use than any text-book theory.

"Soil mechanics" might be an area to look into. I know little about it - except that I have seen a 500yard length of 60 foot embankment taken out by water saturation - the entire Up Line of a double track embankment was taken out as precisely as if someone had used a giant cake slice. The ends and back of the space were vertical and clean. The Down line was untouched and capable of carrying normal traffic. The "missing" soil had spread out completely flat across football fields.

Somewhat differently - where the new bridge is at Crewe on the Stoke line they had previously had deep wells - about 5inches in diameter (by sight/memory) that provided monitoring of the water table... Now there's another thing - water tables - and what happens when anything is done to change them...

 

[Trackbedjolly]

I take it you are asking about stability of existing embankments rather than designing new ones?

From my experience as an Railway Earthworks Asset manager in the early 2000s I would say that embankment stability is a bit like selling property: there are three important considerations but unlike property they are not location, location, location but drainage, drainage and drainage.
OK that is an oversimplification as there are holes dug by rabbits and badgers, unstable trees as well as sensitive clays which respond unfavourably to dry weather, etc but from what I saw about 99 problems out of 100 the cause was too much water. Extreme rainfall events caused some big problems on the railways at that time. 20mm per hour of rain falling over a small area for 3 hours is enough to wash out tracks big style as it causes flooding of various types.

The other type of problem which could occur in an extreme cold situation is where there is a rock-fill embankment. Then the fill material could suffer degradation after repeated freeze-thaw cycles leading to settlement. I am not aware that this has happened but it is at least a theorectical possibilty.