Fatigue properties of intact sandstone in pre and post-failure and its implication to vibratory rock cutting

The pre-and post-failure fatigue properties of intact sandstone subjected to uni-axial cyclical loading in the laboratory is presented with its possible implication to vibratory rock cutting. The fatigue results subjected to sinusoidal, ramp and square waveforms at cyclic loading frequency of 5 Hz and peak amplitude of 0.05 mm is discussed herewith. It is observed that fatigue behaviour is a function of the dynamic energy of the load and the shape of the waveform. From the presented results, the practical significance of the behaviour of rock and rock masses within the excavation systems subjected to cyclic loads, especially in the vibratory rock cutting is put forward. To substantiate the cyclic breaking of rock under vibratory loading condition, a numerical simulation results using discrete element code is presented. Two loading cases were considered. In the first case, the wedge pick was loaded non-cyclically (monotonically), and in the second case it was loaded dynamically under cyclic sinusoidal loading at 50 Hz frequency. A load-deformation curve under monotonic (non-cyclic) loading condition and cyclic loading conditions were examined. The model showed a drop of about 25% in peak strength in the case of cyclically loaded wedge pick compared to monotonic or quasi-static loading of the wedge pick cutting. It is inferred that the vibratory loading has benefits in fracturing rock at relatively lower load compared to conventional loadin