Micromechanical Background to a Strain Space Multiple Mechanism Model for Sand

Abstract

By theoretically studying the behavior of sand through the mechanics of assembly of spheres, a micromechanical background is offered for a constitutive model of a generalized plasticity-multiple mechanism type defined in strain space (Iai et al., 1992a). The study confirms the existence of the hierarchical structure in the stress, concept of which played a fundamental role in deriving the aforementioned model. The basic level of partial stress contribution is associated with the contact forces of a specific direction. This level of partial stress contribution represents a fundamental “element” of stress. The second level of partial stress contribution is the one associated with the virtual plane strain mechanism and obtained by combining the basic level of partial stress contributions. The stress in the three dimensional space, which is nothing but a stress of usual definition, is the highest level and obtained by combining the second level of partial stress contributions. This type of structure is believed to play a crucial role on the cyclic behavior of sand involving the effects of rotation of principal stress axis directions.