Plastic barrels as a retaining wall?

I'm thinking about filling plastic barrels with soil and using them, standing up in a row, as a retaining wall for a sunken hot frame. Even better, I'm thinking about filling them with gravel and soil as wicking barrels AND retaining in the hot frame. Anyone have an idea on how this would work? Would it collapse?

What will be in the middle of the rectangle (?) of barrels?
I have two of the 55 barrel sub-irrigated   planters,they are very heavy when full.
I can see burying the barrels up to top of the reservoir for stability.

Two feet of compost pile, and a foot of earth. The issue would be when I shovel out the compost twice a year.  (And the fact that the compost will not exert as much pressure on their side of the barrels as the earth will. )

Maybe you could fill the barrels with water?  Heavy and the sun will heat them to keep your frame warmer at night.

Yeah,that should be great I think,especially as long as the barrels are filled with something,water,soil,etc.

If you use peat moss,be sure to add lime,or the PH will be terrible for anything other than strawberries and blueberries and such.
I seeded some greens into the barrels I had prepped for blueberries and they barely grew, while the seed that fell on the ground next to the barrels grew like bonkers.
You could cover the hot frame with a hoop house,patio doors, or maybe both.
I would divert any roof water to outside the frame as to avoid cooling things down.

I use 200Litre blue drums, filled with water to create a wall.
If laid a concrete pad 4 inches thick and the width of the drums so there is not settlement into the soil.
The water ensures they discharge heat well after sundown.