Probing the mechanical properties of granite from a microscale perspective

Micro-mechanics of granite is of vital importance because it will contribute to the understanding of the deformation and failure mechanism of granite from a micro-scale perspective. The deformation and fracture properties of rocks are closely related to the mechanical properties of its basic constituents. Nanoindentation tests can be carried out to derive the mechanical parameters of materials, such as Young's modulus, hardness and fracture toughness. Nanoindentation tests on granite, however, is relatively less studied when compared with other types of rocks, such as shale, coal, limestone, etc. Therefore, this article is to fill this gap by performing nanoindentation tests on granite samples. In the meanwhile, extensive finite element simulations have been carried out to perform the inverse analysis. The constitutive model parameters can be gained using the proposed method. The impacts of cap eccentricity (RR), uniaxial compressive strength (σucs), cap hardening law and Young's modulus on the indentation response are investigated. Young's modulus significantly influences the slope of the unloading PP - h curve while the impacts of yield surface (i.e., RR and σ ucs) and cap hardening law on the unloading curve are unobvious. This study is beneficial to the understanding of micro-scale mechanical properties of granite sample and provide a baseline to extract the micro-scale mechanical properties of other rock minerals.