An Experimental Investigation of the Influence of Loading Rate on Rock Tensile Strength and Split Fracture Surface Morphology

Abstract

To investigate the effect of the loading rate on the tensile strength of rock material and the morphology of the resulting split fracture surfaces, three types of rock specimens, namely, granite, basalt and limestone, were collected and tested with Brazilian testing under different loading rates. The tensile strength was measured, and the effect of the loading rate on the tensile strength of the rock material was studied. Digital terrain map models of the split fracture surface were obtained with an optical 3D scanning technique, and the effects of the loading rate on the geometry and morphology of the fracture surface were studied. The influence of the loading rate and tensile strength on the roughness was studied quantitatively by calculating the roughness indices of a fracture surface for all three kinds of rock. The research results show that the rock tensile strength increases with the loading rate. A linear relationship was established in double-logarithmic coordinates to describe the relationship between the tensile strength and the loading rate. Four different roughness indices were used to describe the morphology of the split fracture surface. The analysis results show that the magnitudes of all the roughness indices increase with the loading rate. Additionally, the roughness indices for all three types of rock linearly increase with the tensile strength. This linear trend indicates that it is possible to utilize fracture surface roughness indices to estimate rock tensile strength. The current study may motivate further research on the relationship between the morphology indices of rock fractures and mechanical parameters of the rock.