stepped slope purpose

[blights]

Hello

I come with a simple question... I have seen a few times slopes being developed in 2 or more levels, between a short horizontal length appearing. Maybe someone can explain me the purpose of this? Many times it can be used for road or rail embankments. Why can't just one single slope be established? I might've read that it controls erosion, if yes how.

Thanks
Raul

 

[BigH]

The stepped configuration will lessen the overall slope angle unless you would build at the "average" slope and not the slope above each step.

The stepped configuration also assists in drainage - in tropical climates with monsoons, it is good to have many drains to control the precipitation runoff rather than a single long slope that might undergo severe erosion.

The stepped configuration can also aid in maintenance issues - for easier access if one has a localized problem area that does occur many times.

Usually the berms are not wide enough for roads and the like - typically we see them being in the order of 3 m wide.

Stability analyses will consider overall slope stability as well as micro stability of each intermittent slope.

 

[blights]

Thank you for the explanation, makes perfectly sense

 

[fattdad]

in the realm of rock slopes, folks seem to think the step will minimize the fall height and reduce the consequence of rock fall (i.e., on roadways along the toe of the slope. It turns out that this is often bad engineering. The rocks that ultimately accumulate on the step must be cleared (i.e., every 5 or 10 years) and the rock fall potential when there is a step often results in creating a launching platform.

I'm reluctant to approve a stepped rock slope.

f-d

ípapß gordo ainÆt no madre flaca!

 

[BigH]

Thanks fattdad - I was thinking principally of soil slopes as the diagram he posted was a little "flat" for rock slopes - but you are correct - it is best to let rocks fall straight (nearly straight) down and not "bounce".

 

[blights]

Yes I was not thinking about rock slopes when I made the sketch and I agree with you about the fact that the step might make rocks bounce high.

 

[Panars]

For rock cut slopes with different rock types, we will often put a bench at the top of the less durable unit to provide protection against undercutting a more durable unit lying above. So a limestone and shale rock face with limestone above and shale beneath will have a 3 meter (10 ft) bench at the contact between the limestone and shale.

 

[fattdad]

yes, Panars, we'd agree. Google Grundy, Virginia where the 300-ft (plus) rock cuts show benches for that very purpose.

f-d

ípapß gordo ainÆt no madre flaca!

 

[Panars]

I've been to Grundy, Virginia. Did some work on the Flannagan Dam for the USACE once upon a time.