Unrealistic spike vertical displacements (settlement) on plate elements of plate element in Plaxis 3D

Question

Hi all, 
 I am modelling a raft foundation subjected to a uniform load using a plate element as shown in the picture below. When I draw a line through the center in the longitudinal direction of the foundation to assess the settlement of the foundation. There are spikes (large displacements) at two edges of the raft.

Dennis Waterman · Answer

Dear Nam Nguyen Duc, 
 What makes you think the settlements are unrealistic? It seems to be on the edges of the raft and the raft has forces quite close to the edge. So it might actually be that the edges of the raft are cutting in the soil causing those vertical displacements. That should become clear from the deformation of the raft though. There is only a very small chance these settlements have a numerical reason, it's most likely simply the cause of the loading and deformation of your raft. Please check this first, it may be just a design issue. If not, have you tried the general solutions of slightly modifying Rinter of the interface underneath the raft and/or refining the mesh a bit? 
 With kind regards, 
 Dennis Waterman