Material shear strength is among the most important geotechnical parameters used in the design process for engineers. For soils, soft rocks, and rockfills the determination of the shear strength properties is often accomplished through the use of the direct shear test. Unfortunately, much controversy exists concerning the stress and strain distributions, strength calculations, and failure process within the direct shear test. The objective of this U.S. Bureau of Mines study was to investigate the effect of material properties on material behavior under nonuniform stress and strain conditions in the direct shear test using the finite difference numerical technique. This research illustrated the effects of progressive failure within elastic-plastic and strain-softening materials on shear strength. In particular, this paper describes the numerical simulation of a well-documented earth material within the direct shear test. Within an individual material property model, the effects of changes in stiffness, dilatancy, and strain-dependent yielding were identified and discussed. The analysis of these tasks allows for greater insight into the behavior of materials in the direct shear test so that more realistic material properties can be determined.