A study of compaction bands originating from cracks, notches, and compacted defects

Compaction bands are zones of localized grain crushing and porosity reduction, which form spontaneously in high porosity rock under certain compressive stress conditions. Recent experiments show that compaction bands may nucleate at the edges of notches, holes and cracks subjected to compressive stress. We present an elasto-plastic model, used to investigate compaction band formation under a variety of boundary conditions. When simulating a notched specimen and a specimen with a central hole, compaction initiated at the macroscopic void's tips, and propagated in a step-wise manner, in agreement with experimental results. This step-wise manner of propagation is different from the compaction band run-away observed when compaction bands nucleate from pre-existing compaction bands. In addition, heterogeneity in rock properties, such as heterogeneity in local compressive strength, was found to control the morphology of compaction features initiating from voids.