Lateral pressure from triangular soil mass 3

[Guest090822]

Does anyone know of any guidance on how to treat a "triangular" soil mass that is resting on a vertical wall?

The following is a simplified version of my problem:

The initial analysis is assuming that there is sediment build-up to within 2' of the wall and they treated it as level backfill with an infinite distance.

However, the soil build-up is actually sloped down and away from the vertical wall.

Does anyone know of a good approach on how to determine the lateral force exerted from a triangular soil mass that has known dimensions?

There was really good thread a long time ago (10 years +) where I encountered something similar and a few geotechnical guys had a simple rule of thumb that I can't recall, or find the thread!

Thanks in advance,
Rick

 

[r13]

If you know the properties of the sediment, failure wedge analysis should helps.

 

[PEinc]

Most soil mechanics books discuss and give earth pressure coefficients for sloped ground surfaces. However, if the soil slope angle is steeper than the soil's internal friction angle, the coefficient formulas will not work and you will calculate imaginary numbers for the coefficients. Therefore, either flatten the slope or investigate wedge analysis as r13 suggested.

Because the sediment is building up behind the wall (dam?), it is probably wise to assume a flat ground surface behind the wall.

http://www.PeirceEngineering.com

 

[BigH]

Why not use a Culmann graphical method? Terzaghi, Peck and Mesri (1995) page 251-252

 

[Guest090822]

I was trying to avoid doing any wedge analysis or graphical methods. I just wanted to run a quick check to see if we could get it to pass the sliding check.

I seem to recall - and PEinc, it may have been one of your responses a long time ago where some engineers would "ignore" the sloped fill and treat it "flat" by reducing the sloped fill.

I want to say someone with a lot of experience indicated that they would simplify designs near sloping ground by doing the following:

I was looking do the same to get an idea of how much it would make a difference.

Thanks!

 

[r13]

I consider this is quite simple through a wedge analysis - image the wall is not present, the inclined failure plane can be drawn from the bottom of the wall and intercept the sloping sediment. From there on, everything is static matters. I could be wrong, like to hear others approaches.

 

[PEinc]

TheRick109, your sketch looks like a dam. Dams receive maintenance or dredging very infrequently. Silts continually build up behind the dam. There could be significantly more buildup that will be more critical than the slope you have described. Don't skimp on the design earth load.
The big question about your last sketch is what really to assume for y and your horizontal H. I don't think you will find a reference.
Also do you need to consider ice loading?

http://www.PeirceEngineering.com

 

[Guest090822]

PEinc - we have all the necessary loads and cases as per the US Army Corps on Engineers’ guideance. I just noticed that the silt loading looked too conservative since I’ve been to the site several times and I know the silt gradually slopes away. I was curious if taking the slope into consideration would get us anywhere.

 

[r13]

You may try this for locations far away from outlet with low flow activity. Just a personal thought, no theory/study to backup though.