Investigation of the use of Leeb hardness in the estimation of some physical and mechanical properties of rock materials

Abstract

Uniaxial compressive strength (UCS) and some physical properties of rock materials are very important input parameters used in rock mechanics and engineering. Samples with standard shape and dimension are used in physical and mechanical tests. However, it is difficult to determine the UCS values in case of difficult sample preparation conditions. To overcome this limitation prediction of UCS values from indirect test methods is preferred. One of the most common parameters used to predict the UCS values of rock materials is surface hardness. In this study, the usability of hardness values (HL) of selected ignimbrite, travertine and syenite rocks in the prediction of some physical and mechanical properties were investigated by using the Leeb hardness test which has much lower impact energy than the Schmidt hardness hammer has. Firstly, petrographic and some physical and mechanical properties of the samples were determined and then the HL measurements of all samples were taken. Test results were correlated and correlation equations for dry (gamma(dry)) and saturated (gamma(sat)) unit weights, apparent porosity (n(A)), water absorption (w(S)), sonic wave velocity (V-P) were presented and prediction equation of UCS from HL measurements were proposed. In the context of the study, the effect of L/D ratio on HL measurements were also investigated and minimum length to diameter (L/D) ratio of 1.5 on samples with 50 mm in diameter was suggested for consistent HL measurements.