ABSTRACT
For rock excavation equipment that applies impulse loads, bit spacing is one of the important determinants of rock fragmentation efficiency. The objective was to measure the sizes of the fractured zones and hence, determine the optimum bit spacing for machines that excavate in rock. A scheme for incorporating obtained laboratory test results into the design of booms for rock excavation equipment is presented. Several relationships between wave velocity and various indices of rock strength have been proposed. The objective is to use an impact bit spacing, m, that results in a necessary but limited overlap, e, between the impact-induced fracture zones in brittle rock. Sonic wave transit times through Academy Black Granite and Lac Du Bonnet Granite increased due to the presence of fractures caused by impact loads. Information on fractured zone sizes is to optimize impact bit spacing for energy efficient excavation.
