Hello everyone!

I just want to ask about my problem, which is related to excavations, open pit mine stability, etc. Geomechanics in general. There's something called in situ stress, and below ground it exists. These are applied at opposite faces of our model, and have the same magnitude at opposite faces of the outer boundary of the model. (See pic attached)

So basically, I need to apply a compressive pressure in a face x with magnitude X, and in the opposite face I need to apply THE SAME pressure. Same procedure needs to be followed for the rest of the faces of the box.

The issue is that, they seem to cancel to each other, so the final model is like it was never under the action of in situ stress, and only under the effect of gravity... Is there a way to fix this? it's really frustrating, because I am not getting the results I am supposed to get.

Cheers and thanks in advance. Hope you get my problem.