Examples are presented of aspects of the mechanical behaviour of granular materials which need to be described at the continuum level but which are clearly strongly controlled by the particulate nature of the material. These include: stiffness at 'zero' and small strains, asymptotic states, effects of particle breakage, and intermediate scales. Asymptotic 'critical' states in which shearing continues without further change in stresses or density play a central role in many constitutive models. However, such asymptotic states may not be easily observed in practice. Laboratory tests combined with discrete element modelling show the effects of journeys towards the critical state and show that parameters such as grading and density are still changing slowly at very large strains. Rotation of principal axes is destabilising for the fabric of granular materials and also influences the way in which patterns of localisation form. Acceptance of the particlexontinuum duality is essential for the development of models of these materials.
|Title of host publication||Structures and granular solids|
|Subtitle of host publication||from scientific principles to engineering application|
|Editors||Jian-Fei Chen, J. Y. Ooi, J. G. Teng|
|Place of Publication||London|
|Publisher||Taylor & Francis|
|Number of pages||20|
|ISBN (Print)||0415475945, 9780415475945|
|Publication status||Published - 1 Jan 2008|
Muir Wood, D. (2008). Modelling granular materials: discontinuum-continuum. In J-F. Chen, J. Y. Ooi, & J. G. Teng (Eds.), Structures and granular solids: from scientific principles to engineering application (pp. 21-40). Taylor & Francis.