Prediction of permanent soil deformations due to cyclic shearing with a hypoplastic constitutive model

The prediction of permanent soil displacements due to alternating loading is important for assessing the stability and serviceability of transport network, foundations of machines and wind turbines as well as structures in earthquake regions. The accumulation of permanent displacements due to alternating loading depends on many factors which engineers attempt to capture in a corresponding stress-strain relationship. Typical hysteretic soil behaviour during cyclic shearing and its description with a constitutive model are shown in this article.

The capability of the hypoplastic constitutive model with intergranular strains to reproduce the non-linear and anelastic behaviour is discussed. The determination of the material parameters for describing shear stiffness degradation with increasing shear strain amplitude is considered and, simultaneously, an increase in stiffness after a change in shearing direction. A modification of the hypoplastic constitutive model, including one additional soil parameter, is proposed in order to describe accumulation effects more realistically. The additional parameter can be determined in cyclic shear or triaxial tests. How to reproduce realistically the accumulation of volumetric strains under drained conditions and excess pore pressures under undrained conditions during cyclic shearing is demonstrated.