Bearing or Passive Capacity of Thin Soil Infill

[TLHS]

What the heck is the failure mechanism of a soil or granular material when the passive plane is interrupted. If I've got granular material that's say 4 feet deep and it's going to see lateral load from the left, but there's a concrete wall 3 feet away to the right, how does that work? It can't just be passive pressure because the passive plane is interrupted by the concrete wall and load gets transferred into the wall. It isn't a straightforward bearing problem because the soil isn't fully confined at the top, so there's some sort of failure mechanism where the soil bursts upwards.

This seems like it would be significantly stronger than a soil restrained by passive pressure, but I'm not sure how to get a ballpark capacity out of it.