A phase-field approach for compaction band formation due to grain crushing

Compaction bands are tabular regions of localized compressive deformation with little or no shear offset. Often observed in high-porosity rocks, they can be classified into several subtypes based on their pattern and orientation with respect to the maximum principal stress. The combined effects of material properties and loading conditions on the type of compaction bands that develop are not fully understood, and realistic simulations of their formation are not always successful. In this study, a phase-field approach for capturing the formation and propagation of compaction bands is proposed. The fracture energy utilized in classic phase-field formulations is interpreted to be driven by grain crushing and is herein characterized by breakage mechanics theory. A new decomposition of the free energy function is introduced in which the energy stored by plastic compactive flow drives grain crushing. Depending on the value of the energy release rate, the model predicts different styles of compaction bands that are remarkably consistent with those observed in the field. Numerical simulations demonstrate the role of confining pressure, plasticity, and critical breakage energy on the styles of the predicted compaction bands.

Automated summary

In this study, a phase-field approach is proposed to capture the formation and propagation of compaction bands. By interpreting fracture energy as driven by grain crushing and introducing a new decomposition of the free energy function, the model accurately predicts different types of compaction bands. Numerical simulations also reveal the role of confining pressure, plasticity, and critical breakage energy on the styles of the predicted compaction bands.