The stress-strain relation of cohesionless soil can be modeled with Gudehus-Bauer hypoplastic constitutive model

in which the magnitude and direction of stress increment depend on not only the previous stress state

but also the bulk and direction of current strain increment. For analyzing differences between this model and traditional elastoplastic theory

the linear term and nonlinear term of Gudehus-Bauer model are investigated. The stress-strain relation of Gudehus-Bauer hypoplastic model in different original void ratios is discussed. The results show that Gudehus-Bauer hypoplastic model can consider irreversible deformation without recourse to decomposition of strain into elastic and plastic parts. This model can also embody dilatancy

strain-softening of dense sand and contraction

strain-hardening of loose sand.