Soils have been studied more extensively in terms of strength and stress-strain characteristics than any other particulate material. The theory that H. A. Janssen developed for stored granular material was incorporated into soil mechanics literature when A. Marston used the same differential equation to predict soil loads on buried conduits. Historical development is intended to show the chronological development of ideas relative to the mechanistic behavior of granular materials. The chapter describes specific examples of how these ideas are applied to the design of storage facilities for bulk solids. The behavior of particulate systems is characterized by various types of nonlinear stress-strain relationships, which depend upon the test conditions. The shear resistance of bulk solids is frictional in nature, that is, the shear stress required to cause sliding along a plane within the mass of the material increases with increasing normal stress on the failure plane.