Hypoplastic constitutive equation with internal variables

A new version of a hypoplastic constitutive equation is presented which is characterized by the introduction of a stress‐like internal parameter called back stress. The back stress is a function of the void ratio and of the hydrostatic stress. Using a unique set of material constants, the new constitutive equation describes many aspects of the behaviour of cohesionless soils including the influence of density and stress level. This is demonstrated by a series of verification tests. The determination of the material constants from laboratory tests is described analytically.