A COSSERAT CONTINUUM MODEL FOR LAYERED MATERIALS

Modelling the behaviour of materials consisting of a large number of l ayers is often required in geomechanical applications. In this study, an equivalent continuum model suitable for describing the mechanical r esponse of such layered materials is considered. The model is based on the Cosserat continuum theory and incorporates the moment (couple) st resses in its formulation. The layers are assumed to have equal thickn ess and equal mechanical properties with elastic behaviour. In contras t to the earlier Cosserat models, the possibility of layer interface ( joint) plastic-slip as well as tensile-opening during loading is consi dered. The importance of moment stress in describing the behaviour of such materials is discussed and highlighted through an example. It is shown through numerous examples that when there is a possibility of in ter-layer slip and subsequent layer bending, equivalent continuum mode ls based on the conventional anisotropy theory may not represent a tru e response of the layered materials. The relationship between the larg e-scale (Cosserat) description of the layered material and the fine-sc ale (micro) description of the stress-strain state of an individual la yer is determined. The model is incorporated into the finite element ( FE) code AFENA and several examples of load-deflection problems in lay ered materials are analysed. The Cosserat model is verified against th e explicit joint FE model. Comparison between the two models shows a r emarkable agreement suggesting that the Cosserat model is capable of p roviding an accurate prediction of the load-deflection behaviour of la yered materials. (C) 1997 Elsevier Science Ltd.