Fabric assessment of damaged anisotropic geo-materials using the multi-laminate model

- Developing a simple, fast and practical model for predicting anisotropic behaviour of geo-materials.
- Investigating the effects of anisotropy on different failure mechanism and direction of geo-materials.
- Assessing the effect of applied stresses or strains (induced anisotropy) on fabric of the geo-materials.

Fabric or texture of intact geo-material affects its degree of anisotropy, and results in various mechanical properties in different orientations. It is a complicated problem, and it is important to consider fabric variations under different stress paths. Applied stresses change the fabric of the material, and change its rigidity and stiffness in different directions. Classic models are developed based on the invariants of stress tensor. These invariants do not carry the characteristics of the material in different directions, and most of the directional information of the material behaviour is being missed. To overcome these issues, a simple methodology was outlined to predict the behaviour of a geo-material in various orientations due to anisotropy. Multi-Laminate model, which is capable of considering the behaviour of material in different directions, was utilized as the framework of this study. Three damage functions and three ellipsoids were used to consider degradation of the material and spatial rigidity distribution around a point, respectively. The shape of the ellipsoids might be changed during the loading history due to fabric evolution. Model results were compared with some tests results. Mechanism of failure was predicted via investigating the damage functions. Fabric evolution was assessed, and rigidity variation of material under a cyclic stress path was investigated.