Georgrid in gravel under slabs in very high basements?

[Bammer25]

I do a lot of critical slope foundations where you have a typical 10’ front wall and then a basement where the grade falls off pretty quickly. You end up with anywhere from a daylight rear wall (ideally) or a worst case of 15 feet or more of gravel under the slab up against the rear and side walls.

Is there any benefit to using layers of geogrid every few feet and compacting the 57 stone? Would that improve stability enough to matter? These are typically 30’x30’ ish cabins.

Many around here just start stacking geofoam when they realize their walls are under built but I’m not convinced that’s a perfect solution.

 

[Bammer25]

I added a typical sketch

 

[XR250]

I just got done with one of these and ended up using a suspended slab.
Was cheaper than any other option and the customer got a bunch of free storage space and a storm shelter(ish).

 

[Bammer25]

Did you use steel beams and cast the slab on decking? I have done a bunch of those. They are completely against that route for this project.

In theory will the geogrid help? Does it have to be attached or can it float?

 

[XR250]

Yes.
Don't know about the Geogrid.
Regardless, I would make sure you don't have a global stability issue with the foundation.