Microscopic understanding of dilatancy in cohesionless soils

Expressions for stress ratios and plastic strain increment ratios are derived from the planar me chanical analyses of soils consisting of particles of regular elliptical shape, circular and crawler belt shapes, and of irregular shapes. On this basis, a microscopic dilatancy model is established depending on the intrinsic characteristics of soil materials including particle shape, particle size or gradation, and particle packing or fabric. It is shown from the model analyses that when establishing the macroscopic state-dependent dilatancy theory, the concept of the state should not be limited to only the void ratio state parameter describing the soil particle packing. Other macroscopic state parameters capable of reflecting the particle shape, size and gradation should be also included.