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Restrained Retaining Wall (Sort of)

Restrained Retaining Wall (Sort of)

Restrained Retaining Wall (Sort of)

See attached pdf. I have a retaining wall that, contrary to normal, is not resisting external soil pressure, but internal soil pressure from backfill that pushes outward.  In my worst spot I have 87" of unbalanced load pushing outward.  My concern is that while I have a slab present at the top, which I can tie in with dowels, to resist sliding at top - I have no slab at the bottom to resist sliding.  Passive soil pressure (30" of cover on toe side) and friction is not enough even if I put a really wide footing in.  

What are my options?
I can think of: External Butresses, Internal Butresses, loose the backfill and put a crawl space... As this is a rectangular garage area (yeah vehicle load to boot) I thought of some sort of below grade reinforced footing to tie opposite sides together similar to what we do on steel moment frames to resist thrust, could this work?  Any other thoughts???

RE: Restrained Retaining Wall (Sort of)

Yea.  "loose the backfill and put a crawl space"

If you are having that much of a problem with sliding here, lose the height difference and put in a crawlspace.  That's the simplest solution I can think of, and it also provides a better area to run water, heat, plumbing, etc.

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Restrained Retaining Wall (Sort of)

I wouldn't be as concerned about the wall kicking out as I would be about the fill behind the wall settling and causing the slab to drop.  Unless you use something like flowable fill or stabilized sand, further consolidation after construction is inevitable.  Agree with Mike.  Best to build it as a suspended slab over crawl space.

RE: Restrained Retaining Wall (Sort of)

Some other ideas:

Your footing doesn't appear to be that long - perhaps a wider footing serving as a horizontal concrete beam, spanning between the intersecting walls could be used to laterally support the base of your wall.

Add an interior gradebeam at the midspan of that horizontal beam/footing to extend back to the main structure as a tension tie, cutting the horizontal span in half.  (make sure the load gets "out" of the structure by following the full load path).

Deepen your footing to get passive pressure to work.

I agree with the others that consolidation would be a very significant issue.


RE: Restrained Retaining Wall (Sort of)

The suspended slab and crawl space appeals to me.  I think it is better and probably more economical than placing up to seven feet of fill.


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