Multiscale plasticity of geomaterials predicted via constrained optimization‐based granular micromechanics

• Published in: International journal for numerical and analytical methods in geomechanics 2022-03, Vol.46 (4), p.739-778
• Main Authors: Bryant, E.C., Bennett, K.C., Miller, N.A., Misra, A.
• Format: Article
• Language: English
• Subjects: Calibration; Coefficient of friction; constitutive behavior; Constraints; Elastoplasticity; Frameworks; Geomaterials; granular micromechanics; Homogenization; Macroscopic models; Mechanics; Micromechanics; microstructures; multiscale; Optimization; Plastic properties; Plasticity; variational calculus; Variational methods; Yield criteria
• ISSN: 0363-9061; 1096-9853
• DOI: 10.1002/nag.3320

A general framework to derive nonlinear elastic and elastoplastic material models from granular micromechanics is proposed, where a constraint‐based variational structure is introduced to classical grain contact‐based homogenization methods of hyperelasticity. Like the classical hyperelastic methods, reference solutions for closed‐form hyperelastic material models are analytically derived from the grain‐scale contact mechanics. However, unlike prior methods, the proposed homogenization framework defines closed‐form hyperelastoplastic material models that extend multiscale variational methods to granular plasticity. The proposed framework is used to develop novel granular micromechanics‐based macroscopic models for a Mises type solid, Drucker–Prager type plasticity, and grain‐contact cohesive‐debonding with a deviatorically and volumetrically coupled nonlinearly elastic response. Macroscopic plastic parameters and yield criteria are explicitly related to their microscale counterparts, for example, the friction coefficient governing intergranular slip. Numerical examples and comparison to measurements from the literature, including triaxial compaction of concrete, are provided to investigate model predictions and demonstrate calibration to experimental data.