Micromechanical model of weakly-cemented sediments

Experiments indicate that the bulk stiffness of weakly-cemented granular materials increases significantly with the applied load, a nonlinearity which is not captured by most micromechanical models. Here, we study the deformation of weakly-cemented materials through grain-scale simulations. We show that the frequently-made assumption of linear-elastic cement and intergranular contact area which varies according to a Hertzian-type model cannot explain the observed nonlinearity of the bulk response. We introduce the micromechanical effect of mechanisms such as closure and opening of microcracks, granular cement and material heterogeneity through an effective contact stiffness which depends on the local deformation. We find that an exponential dependence between the effective stiffness and the local deformation, with a high exponent value, provides bulk stiffness which is in good agreement with experimental data. The inability of models with weaker intergranular stiffness-deformation dependence to reproduce the experimental data demonstrates the highly-nonlinear nature of the intergranular deformation. Our results highlight the importance of accounting for grain-scale mechanisms in modeling granular materials, and provide a plausible explanation for the nonlinear behavior of weakly-cemented sediments. Copyright (c) 2012 John Wiley & Sons, Ltd.