In some cases when using a PLAXIS 3D AE model with tunnels, it can happen that the external water pressures (water loads from a water body acting on a free surface) are not applied correctly on the tunnel circumference. This is important for when for instance modelling a grout pressure by using a user defined pore pressure.This, of course, will not give the expected results of an analysis.
You can see this happening when inspecting a phase’s preview or its result, for which part of the geometry does not have external water loads applied at all.
Figure 1. Example of missing external water loads
This issues is resolved since PLAXIS 3D 2016.01
When the above happens in your model, it can be solved by splitting the existing polycurve of the tunnel into two parts. The following can be done, for example:
Figure 2. Horizontal subsection line to intersect the existing tunnel