Coulomb Theory & Cantilevered Retaining Walls

[DCBII]

Every cantilevered retaining wall example problem I can find seems to use a horizontal backfill and Rankine theory. I'm trying to get a better understanding of retaining wall design using Coulomb theory. I have a few questions.

All the textbook derivations of Coulomb theory I've seen show the soil failure wedge against a sloped wall (one with a "rake angle") with no heel (and thus no "vertical back"). How does the heel influence the shape of the failure wedge when I'm checking overturning? Do I assume the "vertical back" is one of the failure wedge planes, rather than the wall itself? How does this affect the value of delta (friction angle)? What should I be using for delta?

How does the wall slope ("rake angle") affect overturning calculations on a wall with a heel?

Thanks.

 

[GTeng]

I suggest you download the Corps of Engineers Engineer Manual for Retaining and Flood Walls. It is available for free download. They have a discussion of the wedge of soil on the heel. They do not discuss the problem of friction you mention though. It seems like it is relatively conservative and generally recommends very low friction be considered.
The inclination of the back of the wall changes orientation of the resultant, because Coulomb approach assumes normal resultant to the wall (for no friction).

 

[RFreund]

Could you maybe post a sketch? I believe I under stand your question but I want to make sure. By 'rake angle' do you mean the same as 'batter' or lean of the actual wall? Are you referring to something similar to a concrete cantilevered retaining wall with a sloping backfill (with or without batter?)

EIT

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