Existing Slab w/ new basement retaining wall addition

[Elizabethstructures2]

I am designing an addition to an existing house. They are only keepint the garage slab, and i am doing everything else new. Directly behind the garage, i have designed a retaining wall for a 6' basement/crawlspace. The more i look at it, the more i thing i need to account for loads from the 'on grade' wall footing reactions. Does anyone have any experience in this and what i should do to confirm my retaining wall design?
I attached my scenario. Each perpendicular wall has loads as noted on picture:

 

[jhnblgr]

How do you plan on not undermining the garage slab?

You will have live load surcharge on the wall backside potentially. Likely little to no real impact on design due to shallow height but figure the font axle to hood and verify the angle to the wall.

Best idea is to rip the garage slab out and run it over top of the proposed wall then pour a curb wall above. To keep framing above slab elevation.

 

[Ron247]

I am having a hard time following your drawing. I cannot tell what all is existing versus new. Also, cutting sections at each interface of old to new would help. This would include new and old foundations.

Is there currently a solid wall where new meets old in the garage area or is that the garage door area?

 

[Elizabethstructures2]

Thanks for looking at it, I think the only way to build this new retaining basement wall is to demo at least 2' of that existing slab. There doesn't seem to be a way to construct without undermining the existing slab and wall footing.
Here is a section:

 

[hemiv]

You will want to account for the weight of the slab and live loads on the slab, as well as reactions of any footings near the wall. Check out the California Trenching and Shoring Manual for a good reference on how surcharge and live loads affect soil pressures. And check in your foundation design reference books for the Boussinesq method, which the info the Caltrans manual is based upon.

I would make sure the top of the new basement wall is adequately braced! And pay special attention to how the garage slab and footings will be supported before the wall is poured and cured! That might be the most difficult part, I'm not entirely sure how I would approach that. Maybe move the new retaining wall out a bit so it's not all falling on the same line. If you have a contractor already selected, ask them what they can do!