A review on rock hardness testing methods and their applications in rock engineering

This paper aims to discuss the recent development in rock hardness testing methods and their applications in rock engineering and geological studies. Hardness is one of the essential physical characteristics of minerals and rocks, with dominant effects on rock mechanics and excavatability. In this paper, all available rock hardness testing methods are classified into main categories: static and dynamic methods. After that, standards and testing procedures have been briefly discussed using various literature. The review clarifies the dominant factors that affect the rock hardness as well as physicomechanical characteristics, which affect the hardness. The correlations between different hardness testing methods are analyzed using regression analysis, and their interconnections between them are presented. Also, the applications of hardness scales in the assessment of rock excavatability and machinability have been investigated. In total, it could be concluded that dynamic hardness testing methods have been widely applied in rock engineering. However, the relative standards and field measurement procedures have not been developed well. Future research must incredibly be focused on this lack of past studies and should try to develop reliable models for the prediction of physicomechanical rock parameters.