Sanjeev Mukherjee you can model geogrids using the geogrid element in plaxis. In the plaxis model elastic, elastoplastic.......material models can be used. Please refer to the literature in here and the plaxis manual.
ok, the easiest way is to model geogrid as element with EA input parameters. But when geogrid is installed in granular material is formed something as beam element because of interlocking effects of grains and apertures of geogrid. How to model this?