Using Residential Foundation Wall as Deadweight for Retaining Wall Overturning

[Signious]

Hello,

I am doing a retaining wall that is 4'-0" offset from the nearby house (concrete cant retaining wall running parallel to a regular poured foundation wall)

I plan on extending the retaining wall footing out and do a combined strip footing, using the dead weight of the house foundation wall to resist the large overturning moment from soil loads - does anyone see a problem with this?

I checked overturning using the additional weight from the concrete foundation wall alone, and checked bearing of the footing using all possible worst case loads (resultant from the retaining wall loads in combination with the house loads from floor and roof coming down thru the foundation wall)

My main concern is about violating the 'incremental collapse' portion of building codes as if the retaining wall were to fail in overturning (somehow...) it would take the whole south side of the house with it.

 

[jayrod12]

a sketch or two would help to make sure everyone is on the same page.

 

[KootK]

Two things:

1) I would make it so that the building foundation would remain viable if the retaining wall were removed in the future.

2) If you're in a cold climate, the retaining wall will likely be far enough away from the main building that it would not be considered part of a heated structure. You'd want to consider a) the impact that frost heave on the retaining wall would have on the main building or b) how to properly protect the retaining wall from frost heave.

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.

 

[dcarr82775]

I my head you have a long narrow 'bin' filled with soil. Retaining wall on one side, foundation wall on the other. If that is the case, I see nothing wrong with it, but like Jayrod said, as sketch would help

 

[Signious]

Hey Kootk and Jayrod:

-Regular house foundation wall is done as a regular lateral bracing as if there were no retaining soil, it is on the high soil side as well so not much of a difference there
-6' frost coverage for the ret wall footing with a deep drainage matt connected to the sump on both the ret wall and house wall (not keen about weeping water to the adjacent property) with a vertical layer of insulation protecting the base of the footing.


unfortunately I cannot attach a sketch right now as we are having very weird and selective problems with our internet DNS in the office.

 

[structSU10]

so the retaining wall will also have a lateral force contributed to it by the house foundation? I would think I may look at boussinesq pressure distribution and may use that as the additional vertical pressure to the heel of the retaining wall (would be less than the full weight) at least if the house foundation tends to only catch the back edge of the heel.