Batters

[Philou]

Yes, yes, chums, sorry to disappoint - it's not a question of what batter to have on your cod but what to have on your model.

 

I have looked in the Modelling thread, and unless I didn't type in the correct key-word, I didn't really find what I wanted.

 

I'm currently doing some 3D designs of my proposed layout and I've been trying to follow engineering practices regarding slopes/batters when drawing cuttings and embankments. As I'm trying to model a real place and the land form over which the line will travel (165 feet AOD to 900 feet AOD) I'm finding that cuttings and embankments are taking up a lot of board real-estate if I follow engineering practice of slopes of 1:1.5 (1 up for 1.5 along). What do you use? 1:1.5? 1:1? 1.5:1? Steeper? Or what looks right?

 

Cheers,

 

Philip

Edited October 9, 2020 by Philou

[eastglosmog]

The slope you need will depend on the nature of the material you are cutting through or filling with.  Brunel cut the slopes of Sonning Cutting (in London Clay) at 1 in 2 (vertical to horizontal) and they famously fell down.  A slope of 1 in 3 (v:h) would be more likely to stand up, although if your line runs across Gault Clay (the stuff found below the Chalk scarp in southern and eastern England) you may need 1 in 6!  Rocky cuttings can be much steeper (1 in 0.5 (v:h) or steeper still).  Chalk cuttings were sometimes cut very steep and the resulting pile of weathered chalk that accumulated at the bottom was carted away every year (as en example from the road network the M40 Stokenchurch cutting was cut on this principle)

1:1 would be unlikely to stand up for long unless you were using granite or similar fill.

It frequently happens that when you survey a slope, it is actually flatter than you first thought - I have often been told a slope is "near vertical" when it is flatter than 1 in 1, so by definition, nearer horizontal!

[Wheatley]

45 degrees or slightly shallower looks ok on a model even if it would not stand in real life, in the same way that a 6 foot radius curve does. It's wrong but your eye accepts it. If you're really short of space shallow rock cuttings can be vertical if the rock type allows. 

 

Edited October 9, 2020 by Wheatley

[Philou]

Thanks for the info. I do have some deep cuttings faced in sandstone, but the rest is in earth/soil. I was quite happy to do the full engineering, but it doesn't half use up space. Up 'til now, I've only been able to see the 'model' in 2D, but having drawn it in SketchUp in 3D, it's giving me a better idea of what to expect. Once the layout starts in the flesh there will be plenty of fine tuning to be done as I feel that on-screen doesn't allow that, whereas you can mould the landscape in the flesh (think carving polystyrene to suit).

 

Cheers,

 

Philip

 

As a PS: If any one has done drawing office work (railways or highways) does anyone recall the correct colours to show cut and fill - I know it's blue and yellow (the real names I forget, except crimson lake which was for new carriageway works), but which is which?

[doilum]

30 degrees* is the real life number unless the cutting is through a solid and stable rock. This is also the angle for loose tipped material like sand or coal. If space is tight try a partial vertical retaining wall  which allows a gentler and more realistic angle above it.

*. This is greatly reduced under persistent wet conditions as tragically demonstrated at Aberfan.

[Philou]

@doilum I remember doing slip circles and the plasticity of soils (the lecturer was one of the former Aberfan engineers of the time ) and the natural angle of repose, a lot I now no longer recall as I had no use of what I learnt. It was a rule of thumb (then) that 45° was considered a maximum - things change. I have made use of retaining walls in the 'Rule 1' area, but I'm in the prototype area (tight radii and the such notwithstanding) and it's all earth embankments leading to a viaduct.

 

Cheers,

 

Philip

Edited October 9, 2020 by Philou

[doilum]

15 minutes ago, Philou said:

@doilum I remember doing slip circles and the plasticity of soils (the lecturer was one of the former Aberfan engineers of the time ) and the natural angle of repose, a lot I now no longer recall as I had no use of what I learnt. It was a rule of thumb (then) that 45° was considered a maximum - things change. I have made use of retaining walls in the 'Rule 1' area, but I'm in the prototype area (tight radii and the such notwithstanding) and it's all earth embankments leading to a viaduct.

 

Cheers,

 

Philip

It was one of those lightbulb moments when my geomorphology lecturer introduced the concept of "angle of repose" almost 50 years ago. I suddenly imagined the piles of loose tipped coal outside miners houses in my childhood and the idea stuck. Once demonstrated it cannot be "unseen" and this natural angle is suddenly obvious in real life..

[Philou]

Funnily enough, it was almost 50 years ago that I did my civil engineering course!  We had the piles of coal in our back lanes too.

 

Anyway, I'm off to find my natural angle of repose - 90° to the vertical ..............

 

Toodle pip

Edited October 10, 2020 by Philou

[Philou]

Thanks chaps and chapesses that made the suggestions and information that has proven useful. I have tried 1:1.5 and 1:1 on the virtual model and for the moment it's looking as if 1:1 has it. Here's a 'module' - it's a double track main-line on a rising grade away from a viaduct to pass over the single line branch falling behind it. I'll post the whole thing up later - it's taking a day per module (the visualisation part of threading the track(s) through the land form is doing my head in) :

 

 

Cheers,

 

Philip

[Metr0Land]

Needless to say there's a prototype for everything.  These near vertical faces (don't know what the material is - chalk?) can be seen on the LGV Est just west of Pagny sur Moselle, but there are quite wide trenches beside the line to catch any debris that breaks off.

 

 

[doilum]

39 minutes ago, Metr0Land said:

Needless to say there's a prototype for everything.  These near vertical faces (don't know what the material is - chalk?) can be seen on the LGV Est just west of Pagny sur Moselle, but there are quite wide trenches beside the line to catch any debris that breaks off.

 

 

"Solid and stable geology..." Chalk or limestone would be a good bet.a

Edited October 10, 2020 by doilum
Additional information

[Edwin_m]

Many of our Victorian railways used slopes far steeper than would be used for new infrastructure today.  That's part of the reason why we have so many disruptions from landslips.  Conversely, where space is limited a modern slope may use techniques such as soil nails to allow it to be steeper than otherwise.  

Edited October 10, 2020 by Edwin_m