PLAXIS 2D AE.00 and PLAXIS 2D AE.01: When applying free field boundaries at the vertical model boundaries with a fixed base (Dynamic bottom boundary set to None) and an interface at the bottom of the model, the free field boundaries will change into viscous boundaries during the calculation.
The conditions for free field boundaries to wrongly change into viscous boundaries are:
Note there is no problem with compliant base boundaries if an interface is defined at the base and the dynamic boundary condition for the base is set to compliant base.
This issue is now solved in PLAXIS 2D AE.02