How Does Heterogeneity Control Strain Localization Patterns in High‐Porosity Rocks?

We aim to explore how heterogeneous porosity and grain size contribute to strain localization patterns in highly porous rocks based on phase-field simulations. The strain localization patterns, including shear bands, dilatation bands, and compaction bands, are commonly observed in geological field studies and laboratory experiments. An elastoplastic phase-field model is developed, where the driving forces are formulated considering both the brittle breakage and ductile dissipation to capture the evolution of strain localization patterns. We distinguish between brittle-like fracture released energy (i.e., grain breakage and crushing) and plastic-like dissipation energy (i.e., grain friction and rearrangement) during the strain localization process. The heterogeneity in porosity and grain size is represented by a heterogeneous distribution of consolidation pressure, which is mathematically related to the porosity collapse, resulting in the constitutive responses during strain localization. We proceed to investigate the effects of confining pressure and the degree of heterogeneity on the formation of strain localization patterns, including the simultaneous occurrence of shear bands, dilatation bands, and compaction bands, through a series of simulations.