Evaluation of the performance of a breakage model for high porosity Haubourdin chalk

We examine a new continuum micromechanical approach to predicting the macroscopic mechanical responses of Haubourdin chalk under various load conditions. The approach is based on a simple breakage model that accounts for an evolving microstructural degradation through coccosphere crushing with only five physically meaningful parameters and one grading index. The model correlates the intrinsic failure mechanisms including the coccosphere crushing, pore collapse and plastic shearing that are identified by corresponding internal variables within thermodynamic framework. On this basis, numerical predictions of the stresses and strains are examined against their experimental counterparts as well as the results from an existing continuum model. Parametric studies are further conducted to investigate the effect of the model parameters. The favourable agreements in various conventional and complex compression tests indicate a satisfactory performance of the breakage model, highlighting the importance of capturing the microscopic degradation mechanisms when building a constitutive model.