Discrete Element Modeling of Sphere Indentation in Rocks

摘要

Fragmentation mechanism in sphere indentation was explored numerically using the discrete element code PFC3D~?. The fracturing sequences were analyzed in a face-centered cubic (FCC) crystal structure and a randomly generated particle assembly with material properties similar to those of hard rocks such as granite In the crystal structure, development of the Hertzian cone crack and the damaged zone underneath the indenter was followed by nucleation of a full penny-shaped median crack. In the randomly generated sample, the Hertzian cone crack was no longer evident. Half penny-shaped radial cracks instead of the median crack formed. Depending on the state from which unloading of the indenter started, a deep saucer-shaped lateral crack may initiate and propagate in both the crystal structure and the random packing. Locations of the lateral crack initiation were observed to be at the side instead of the base of the damaged zone. The tensile stress field developed near the free surface during the unloading stage was responsible for the formation of the lateral cracks.