A numerical investigation of wall pressures generated by bulk materials stored in hopper-silo combinations is presented. Emphasis is placed on incipient flow type pressures on inclined hopper walls. The technique used incorporates a Drucker-Prager-type elastic, perfectly plastic model for an assumed granular bulk material and Coulomb-type friction for the boundary interface. A double-layered iterative scheme with a relaxation function is used to model proper contact friction interfaces as well as material nonlinearities. A parametric study is carried out to determine the validity of the approach.