When using the interpolate pore pressures function for a soil cluster to determine the pore pressures, adjacent interfaces should use the same interpolated pore pressure distribution.
However, for PLAXIS 2D 2015, 2D 2016 and 2D 2017 (2017.00, solved in 2017.01), in the case that the interpolate pore pressure function is used for multiple vertically aligned soil clusters with an adjacent interface, in some cases, the pore pressures might be incorrectly interpolated in the interfaces. A typical geometry in which this goes wrong can be found in the image below.
In the final calculation results, you should check if these (steady state) pore pressures in the interfaces are correctly determined: double-click the interface and check the steady state pore pressure distribution:
This issue has been resolved in PLAXIS 2D 2017.01.
We advise checking the interface's pore pressures carefully after running the calculation (the preview does not show this), especially when using the interpolate pore pressures function.
In order to prevent this problem in PLAXIS 2D 2015/2016/2017 (Version 2017.00), you can use one of these two options:
You need to change the geometry around the interface's end. The simplest approach would be to just draw a horizontal line connecting the interface's end with e.g. the boundary to make two separate clusters at the opposing side of the interface. See the images below.
A second option is using the option of user defined pore pressures in these clusters in favour of the interpolate option: