Fatigue properties of intact sandstone samples subjected to dynamic uniaxial cyclical loading

Abstract

In this paper, the fatigue behaviour of intact sandstone samples obtained from a rockburst prone coal mine and studied under dynamic uniaxial cyclic loading in the laboratory is presented. Tests were conducted on dry and saturated samples with loading frequencies ranging from 0.1, 1 and 10 Hz and amplitudes of 0.05, 0.1 and 0.15 mm. From the laboratory investigations, it was found that the loading frequency, as well as the amplitude, was of great significance and influenced the rock behaviour in dynamic cyclic loading conditions. The dynamic fatigue strength and the dynamic axial stiffness of the rock reduced with loading frequencies and amplitude. The dynamic modulus was found to increase with the loading frequency but decrease with the amplitude. In the case of the saturated samples, it was found that the dynamic fatigue strength reduced by approximately 30 per cent, while the dynamic Young's modulus reduced by about 20 per cent. From the presented study, the dynamic energy was found to be independent of the testing conditions while other rock properties were found to be dependent on these. Finally, it was concluded that rock would more readily succumb at low frequencies and amplitude than at high frequencies and amplitude for a given energy availability.