The normal group_materi_plasti_mohrcoul does only limit shear forces, and doesn't care about any tension stresses. That normally isn't a problem since in geotechnical calculations the stress are compressive anyway.
With this group_materi_plasti_mohrcoul_tensioncutoff you can cutoff, however, any tensile stresses beyond the apex. Activate this by setting switch to -yes.
Activating this cutoff option may lead to a more troublesome convergence behavior.