create shell planar in 2D model ? (Abaqus 6.13)

Hi,

I have modeling a ground in abaqus and simulated earthquake. will i need allow infinite elements in the laterals model (left and right). In other examples i see in the features (module part) created  "shell planar" en the places to create the infinite element (edge, no plane)... so .. how its made ?

thanks. 

PD: Me english is terrible, sorry.