New Retaining Wall
New Retaining Wall
(OP)
Hello all,
I was asked sometime ago to design a new retaining wall on one side of a garage, and the other side would keep the existing concrete wall. During demolition, the contractor discovered that the existing 12" concrete wall that was intended to remain actually had 6" of unreinforced glory to it. The solution the owner and the contractor decided was to place a new wall in front of the existing wall to avoid the necessity of temporary shoring plans, etc.
Question is: The new retaining walls will now have two separately poured slabs, both with their independent keys to combat sliding. They will be abutting one another.
Should I dowel one retaining wall into the other?
Is there a specific calculation that comes to mind that you would recommend I consider?
Additional notes to consider: There's an 8" concrete slab specified to sit above the garage - the connection between the stem of the retaining walls and the slabs will have some fixity. Plus, there will be a significant amount of concrete dead load applied to those stems as well, which have been accounted for, but as an FYI. The water in the soil is a matter of high concern.
Thanks,
Rod
I was asked sometime ago to design a new retaining wall on one side of a garage, and the other side would keep the existing concrete wall. During demolition, the contractor discovered that the existing 12" concrete wall that was intended to remain actually had 6" of unreinforced glory to it. The solution the owner and the contractor decided was to place a new wall in front of the existing wall to avoid the necessity of temporary shoring plans, etc.
Question is: The new retaining walls will now have two separately poured slabs, both with their independent keys to combat sliding. They will be abutting one another.
Should I dowel one retaining wall into the other?
If so, how deep would you suggest I dowel the rebar? A tension splice would seem to call out for something like 26" but that seems unnecessary (#5 bars @ 12" O.C. top and bottom at the toe of both retaining walls, if my memory serves me...)
Should I provide a joint instead?Is there a specific calculation that comes to mind that you would recommend I consider?
Additional notes to consider: There's an 8" concrete slab specified to sit above the garage - the connection between the stem of the retaining walls and the slabs will have some fixity. Plus, there will be a significant amount of concrete dead load applied to those stems as well, which have been accounted for, but as an FYI. The water in the soil is a matter of high concern.
Thanks,
Rod






RE: New Retaining Wall
RE: New Retaining Wall
RE: New Retaining Wall
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: New Retaining Wall
RE: New Retaining Wall
Is this six inch wall or it's footing sandwiched between the two retaining wall slabs that you mean to dowel together? Would you be doweling through those elements. Are the structures on either side contiguous occupancy's such that it would be important to minimize differential vertical settlement?
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I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: New Retaining Wall
And the surrounding structures are strictly residential.
RE: New Retaining Wall
1) If you keep both keys, I would add some dowels to limit differential vertical settlement. I'm not sure how one would calculate the demand on those dowels without getting ridiculously fancy. I'd just throw in two rows of 15M@300 along the 18" face of the new slabs.
2) If the "original retaining wall" currently exists in the field I'd definitely forgo the key on the new retaining wall footing. Same dowel requirements as #1.
3) If neither retaining wall has been constructed, I would consider switching to just old fashioned, top restrained basement walls rather than cantilevered retaining walls. No keys, no 18" footing, and much less rebar. Just a slab on grade restraining the bottoms of the two walls laterally. Who knows though, maybe you've chosen the path that you have because you're tanking the structure as a result of the water issues that you mentioned above.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: New Retaining Wall
Thanks for the other recommendations.
RE: New Retaining Wall
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.