The Coupled Influence of Surface and Internal Crack Propagation on Rock Breakages by Indentations in Biaxial States

Abstract

To investigate the coupled influence of surface and internal crack propagation on rock breakages, indentation tests in biaxial states were conducted to generate various internal cracks and surface cracks that may determine the rock breakages between indenters. Crack observation shows that the increase in the maximum confinement (\(\sigma _{1})\) promotes surface crack propagation when the minimum confinement (\(\sigma _{2})\) is fixed; simultaneously, the initiation and the deflection angle of internal cracks increase. The increase in \(\sigma _{2}\) when \(\sigma _{1}\) is fixed restrains surface crack propagation, but hardly influences internal crack propagation. In addition, the propagation tendency of internal cracks in tests agrees well with previous studies and the tendency of surface crack propagation is validated by a theoretical analysis. Moreover, the following analysis demonstrates that the effective connection by internal cracks and the sufficient incisions by surface cracks significantly determine the chip and the groove formation. Obtained groove volumes indicate that groove volumes are positively related to the surface crack propagation.