When you have defined a geogrid material dataset with Elasto-plastic behaviour in PLAXIS 2D 2016 or earlier, and you open the Plaxis project in PLAXIS 2D 2017, Plaxis incorrectly changes the material behaviour of this geogrid material dataset to Elastic.
Figure 1. Elastoplastic material type for geogrid materials
This means that the geogrid dataset does not have any elastoplastic material behaviour, and will just behave elastically without any strength limit.
This issue is now resolved in PLAXIS 2D 2018.
When using PLAXIS 2D 2017, when opening files created with older versions, please verify that the correct geogrid material behaviour is used.When having the original file, you can use the PLAXIS 2D 2016 Viewer to check the originally used material dataset via the menu item Project > Material information, and then choose the geogrid materials. This Viewer is available here.
Plaxis Viewer - standalone program to view results