Shear bands with characteristic spatial patterns observed in an experiment for a cubic or parallelepiped
specimen of dry dense sand were simulated by numerical bifurcation analysis using the Cam-clay plasticity
model. By incorporating the subloading surface concept into the plasticity model, the model became capable
of reproducing hardening/softening and contractive/dilative behavior observed in the experiment. The model
was re-formulated to be compatible with the multiplicative hyperelasto-plasticity for nite strains. This
enhanced constitutive model was implemented into a nite-element code reinforced by a stress updating
algorithm based on the return-mapping scheme, and by an efficient numerical procedure to compute critical
eigenvectors of elastoplastic tangent stiffness matrix at bifurcation points. The emergence of diamond-like
and column-like diffuse bifurcation modes breaking uniformity of the materials, followed by the evolution
of shear bands through strain localization, was observed in the analysis. In the bifurcation analysis of plane
strain compression test, unexpected bifurcation modes, which break out-of-plane uniformity and lead to
three-dimensional diamond-like patterns, were detected. Diffuse bifurcations, which are difficult to observe
by experiments, have thus been found as a catalyst creating diverse shear band patterns.