New approach for assessing uniaxial compressive strength of rocks using measurement from nanoindentation experiments

Abstract

The uniaxial compressive strength (UCS) of rocks is an essential input parameter for engineering design in mining and civil engineering. This research aimed to investigate the relationship between nano-mechanical properties and macroscopic mechanical properties that result from microstructural constituents of rock materials. Grid nanoindentation technique was applied to a small sample volume to measure nano-mechanical properties such as hardness (Hi) and elastic modulus (Ei) of bulk and major mineral constituents of granite and carbonate rocks. The material Hi and Ei were compared to UCS of the rocks and related to their mineral composition and microstructure, which were detected by X-ray diffraction and petrographic thin sections analysis, respectively. The results show that the mean UCS of the investigated materials correlates well with bulk and major mineral hardness and elastic modulus, with granite showing the highest values, followed by limestone and dolomitic marble. The potential correlations between the UCS and Hi and Ei were investigated using simple regression and multiple linear regression analysis. Except for the weak correlations obtained from dolomitic marble (UCS-Ei), the results show noteworthy correlations between UCS-Hi and UCS-Ei with R2 ranging from 81.5 to 97.5% along with good statistical indices (RMSE and VAF), the best correlation being obtained using MLR. Due to constraints associated with the assessment of standard specimens for compression tests as well as existing indirect methods of determining UCS, the indentation test could be considered a potential means to estimate the UCS from pieces of rock for proper design in mining and civil engineering projects.