Effects of freeze-thaw treatment on the dynamic tensile strength of granite using the Brazilian test

The deterioration mechanism and dynamic tensile properties of rock subjected to the effects of freeze-thaw cycles are investigated in this study. Brazilian disc granite specimens are treated by 0, 30, 60, 90 and 120 freeze-thaw cycles. Freezing and thawing temperatures are −20 °C and 20 °C respectively. The microscopic damage in the rock samples induced by freeze-thaw treatment is detected by the nuclear magnetic resonance (NMR) technique. T2 spectrum and magnetic resonance imaging (MRI) are used to analyze the effect of freeze-thaw cycles on the pore structure of rock samples. Brazilian splitting tests are performed by a split Hopkinson pressure bar (SHPB) system to measure the dynamic tensile strength of granite and to investigate the effect of freeze-thaw cycles on the dynamic tensile strength and the dynamic mechanical behavior. A formula for dynamic tensile strength prediction considering loading rates and freeze-thaw cycles is presented to quantify the results. The dynamic failure process of specimen is observed by a high-speed camera, it was found that the rock materials were more susceptible to damage and deteriorate after freeze-thaw treatment compared with the untreated rock.