On the prediction of mucking rates in metal ore blasting

A model for the calculation of the productivity of cyclic excavators is developed. The production rate results as a product of an ideal, maximum, productivity rate (one of the coefficients of the model) times an operating efficiency. The latter is described as a function of three variables (rock strength, nominal bucket capacity and explosive energy concentration) and three more coefficients. The coefficients of the model have been obtained from field measurements in twenty production blasts at two open pit mines, for which mechanical properties of the rock, blasting characteristics and mucking rates were carefully measured. The model is statistically significant and explains up to 90 % of the variance of the production rate measurements.