As shown in the picture, I am simulating a suspended caisson, and I want to obtain a suspension force that will keep the caisson stationary at any depth. At present, my method is to add line displacement at the bottom of the caisson, but if I specify its x, y, and z displacement as 0, the software will not give the corresponding force, so I fixed the x, y displacement at the bottom of the caisson as 0, and the displacement in the z direction is +0.001m, so the software will calculate a resultant force. I have three questions about this:1. Is it reasonable to apply a minimal displacement in the z direction to obtain the suspension force that can make caisson suspended?2. How should I simulate the mud on the outside of the caisson to help sink (caisson is a plate element)?3. In the process of sinking, the interface elements should be activated to the final position of the caisson at one time, or to the place where they are sunk.？
I am not that familiar with simulating caissons in Plaxis but my answers to your questions would be:
1. It seems reasonable. To verify if the obtained result is correct, you can always run a separate analysis later where you specify the force rather than displacement. If the calculations go ok, then you have your result.
2.The simplest way probably would be to do it by weakening the interface to a very low value. If you want to use different interface strength in the long term, you can always set up manual parameters for the interface and change it at a relevant stage.
3. To the place where they are sunk is more reasonable.
Dear Witold
1.Some strange phenomena appeared in the simulation process. First, I did not set the overcut at the bottom of the caisson, in other words, the bottom of the caisson directly contacted with the soil. At the same time, I gave the bottom of the caisson a very small specified displacement upwards, the size of +1mm, and the resultant force was produced by PLAXIS 3D，The sum of the internal forces in the z direction is negative, which is inconsistent with the actual situation. Why does this happen ?
I would appreciate it if you could help me solve this puzzle.
I believe this is the same as this post: Reached total force Fz not realistic