Problem description

The general model boundary conditions for flow, when set to open, will unintentionally overwrite surface settings that should prevent flow through this boundary locally. This includes:

• a closed surface flow boundary
• active interfaces, e.g. when defined under a plate at the top of the model

This is not correct, and gives wrong results for e.g. a consolidation analysis in which the excess pore pressures should dissipate around a plate and its interface located on the soil’s surface.

Solution

When the model allows it, add a dummy soil block (e.g. weightless) so that the supposed to be closed interface is now not located on the model boundary.
This trick does not work for a closed surface flow boundary, since these only work when activated on the model boundary.

This is solved since PLAXIS 3D 2013.00