I have sheets to make to make a soil reservoir, I know the quantity of earth that will be put in front of it, I started with an approximate value of 1.2 tons per m^3.
Here on my example I blocked the bottom of my bent sheet metal in fixed geometry and then I exerted a force distributed on the face where the earth is located...
but I'm not sure of the value used (put pressure? a force?)
In my opinion, this is rather difficult to simulate because earth is not a homogeneous material and it seems difficult to predict its behaviour. If you take clay the earth will hold on its own because of its low "viscuosity" if you take sand then we are a little closer to the behavior of a fluid.
Let's assume that you have the density of the earth and let's assume that it can be assimilated to a "fluid", the force applied to your folded sheet metal is not constant as you defined it here. It's equal to zero at the top of your sheet. It is proportional to the height of the column of earth. The effort increases with depth.
You have to define a pressure afterwards according to the height of the ground to be remembered, your value will change. Your model is quite close to a hydraulic dam if we consider the fluid to be earth. Of course, the earth is not a homogeneous fluid but I invite you to consider it as such. You will also need values such as the density of the earth.
If you have problems calculating the pressure, don't hesitate otherwise you can find this kind of calculation on the internet.