Modelling of the induced and inherent anisotropy of sand

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The stress-strain behavior of non-cohesive soils is significantly influenced by two types of aniso-tropies: the inherent anisotropy, i.e. the initial fabric of the grain skeleton, which is formed during the initial deposition of the soil, and the induced anisotropy which is generated during the loading of the material. Different formation/placement methods of the soil (for example, sand slurry discharge and under water sedimentation for land reclamation projects or wet material dumping from a greater height in open pit mines) lead to different inherent anisotropies in the material. Laboratory tests show a strong dependence of the material behavior on the inherent and induced anisotropy, in particular for loose sand which is typical for land reclamation or open pit mines. This dependence on anisotropy cannot be neglected in failure analysis or deformation prediction. Unfortunately, the constitutive models commonly used do not consider fabric effects. The main objective of this project is to extend a novel hypoplastic model for granular soils in order to incorporate the effects of both the inherent and the induced anisotropy. For this purpose, the model incorporates two tensors, describing the induced and inherent anisotropy of the material. The extended model will be modified and calibrated based on laboratory tests performed on sand specimens prepared by different methods, i.e. they present different inherent anisotropy. With the constitutive model developed in this project, it will be possible to simulate boundary value problems in which fabric or preloading effects are of significant importance.