Experimental investigation of deformation and failure mechanisms in rock under indentation by digital image correlation

Sandstones have been indented by a cylinder till failure. During indentation, the force-penetration curve has been recorded and the full-field displacements on the sandstones’ surfaces have been measured by the nondestructive optical technique of digital image correlation (DIC). By analyzing the results with DIC, the onset of fracture and the crack length evolution have been identified. Just before cracking, DIC analysis has further revealed slip in some regions, which may act as the shearing crack in splitting fracture model. In that sense, adaptation of the splitting fracture model for the present indentation and comparison with experiments suggest that splitting fracture mechanism may be the dominant one in the failure of sandstones under indentation.