ABSTRACT
Granular materials are multi-scale by nature. When subject to shear, a granular material may exhibit complicated macroscopic behaviours that are notoriously difficult to characterise, such as state dependency, strength anisotropy, strain localisation, non-coaxiality, solid-flow phase transition (e.g., liquefaction) and critical state (Guo & Zhao 2013b, Zhao & Guo 2013). These macroscopic responses reflects highly complicated microstructural mechanisms established and evolved at the granular particle level during the loading process. While a granular medium has long been treated by continuum mechanics, it becomes increasingly clear now that a better understanding can only be achieved with the aid of effective bridging approaches linking the micro to the macro scales of the material. Various homogenisation techniques have been developed in material sciences to link different length scales of a material for integrated characterisation of the material behaviour. They are targeted at designing engineered or new materials with identifiable microstructure to achieve optimal engineering performance of various purposes. However, several intrinsic properties associated with granular media exclude the possibility of deriving material properties and predicting the material responses directly from the particle scale through analytical homogenisation methods as the material science branch does.
