Hello，
If in phase 1, there are two layers of soil in the model, but in phase 2, I need to replace the material of the upper soil with concrete, and at the same time, at this stage, I do not want this layer of concrete to cause any pressure on the lower soil. What should be the right thing to do ? I tried to apply a fixed displacement at the bottom of the concrete material but found that the soil at the bottom was still compressed.
I 'm confused. please help me
Hi xin Fang,
As concrete is typically a heavier material than most soils/rock materials, an additional overburden weight is to be expected. In order not to cause any additional pressure on the lower soil layer, the concrete layer should have the same weight as the previous layer you are swapping from.
Answer Verified By: xin Fang
Hi，
Thank you for your kind reply.
But the reality is that I need to excavate a layer of previously soil material and replace the material with concrete to simulate the construction of a prefabricated foundation. It should be noted that at this phase, it is assumed that there are suspended forces holding the foundation in place to prevent it from coming into contact with the soil below the foundation (it can come into contact with the soil on the side of the foundation). So I wonder if it is correct to add fixed constraints (x, y, z) directly to the bottom of the foundation.Or do I need to add an interface at the bottom and add constraints at the same time
Can you help me answer this question? I 'm very confused
Dear Xin Fang,
I think that makes 3 of us. I honestly don't understand what you're trying to model. You want to replace soil by concrete but you don't want the concrete to cause any pressure on the soil. So how is that physically possible, and what do you mean exactly with "no pressure". You want zero pressure as if the concrete is not there, or you don't want pressures any higher than the former soil pressures? The latter can be simply arranged by giving the concrete the same weight as the soil.If you don't want any pressures at all, I guess that means the concrete footing is on piles or so? If so, then model the piles. If not, I don't see how it's physically possible. Actually, if you don't want the concrete to give any pressure on the soil, why do you model the concrete at all? Just excavate and done.So maybe if you would explain a little bit more what you try to achieve instead of letting us guess in the dark, we can better help you.
With kind regards,
Dennis Waterman