A simple and efficient approach to capturing bonding effect in naturally microstructured sands by discrete element method

A discrete element modelling of naturally microstructured sands is very important to geomechanics. This paper presents a simple discrete element model for naturally microstructured sands with the aim to efficiently capture the effect of cementation between particles (bonds). First, a simple bond contact model was proposed by introducing a rigid-plastic bond element into the conventional contact model for dry granular material. Second, efficient numerical techniques were investigated to implement this contact model into the distinct element method (DEM). Then, a two-dimensional DEM code was developed to simulate a series of isotropic compression tests on the materials of different densities and bonding strengths. Finally, the DEM results were examined in comparison with the experimental data on artificially bonded sands obtained by Rotta et al. (G´eotechnique 2003; 53(5):493–502). In addition, we discussed the yielding mechanism, the Coop and Willson criteria on weak/strong bonding (J. Geotech. Eng. (ASCE) 2003; 129(11):1010–1019) and the strong bonding phenomenon observed by Rotta et al. based on the DEM data. The study shows that the DEM model is able to capture the main features of naturally microstructured sands, such as variations of yielding and bulk modulus against bonding strength or material density. In addition, it is shown that the gross yielding (the yielding defined in terms of strains) is largely related to bond breakage; Coop and Willson criteria are generally reasonable; and the strong bonding in the experimental data obtained by Rotta et al. comes from that their bonded materials start at different points on the same compression line. Copyright q 2006 John Wiley & Sons, Ltd.