Comparison of two integration schemes for a micropolar plasticity

Micropolar plasticity provides the capability to carry out post-failure simulations of geo-structures due to microstructural considerations and embedded length scale in its formulation. An essential part of the numerical implementation of a micropolar plasticity model is the integration of the rate constitutive equations. Efficiency and robustness of the implementation hinge on the type of integration scheme employed. In this paper, two types of algorithms are developed for a critical-state micropolar plasticity model based on cutting plane and substepping integrations procedures. Performance of the two integration algorithms is first assessed in triaxial and biaxial compression tests at an element level. To evaluate the two integration schemes in a strain localization problem, biaxial compression simulations on a slightly heterogeneous specimen of sand are conducted. In all cases the substepping method performs better than the cutting plane method.