Relevance of Shape of Fragments on Flyrock Travel Distance: An Insight fro Concrete Model Experiments Using ANN

Flyrock are fragments that travel beyond the acceptable distances in rock blasting in surface mining. Their occurrence poses a great threat to life and property that may or may not belong to the owner of a mine. Hence, it becomes imperative to predict flyrock travel distance (range) that in turn facilitates definition of the blasting danger zone (or secure area) and take necessary safety precautions. The rock properties, blast design, and explosive loading parameters determine the distance travelled by flyrock. The kinematic equations do not work in such predictions owing to air drag that is specific to weight, shape and size of the flyrock. The importance of shape of the flyrock fragment thus assumes importance. In order to assess the importance of the parameters that determine their effect on the flyrock range, experiments on concrete models were conducted. Complete data of these parameters (136 datasets) were analysed using artificial neural networking (ANN). ANN proved to be a good tool to assess the relative importance and sensitivity of parameters. From the analysis, it emerged that the initial velocity, launch angle, and length of the fragments are of prime importance. Since, spherocity is difficult to ascertain, length of the fragments can prove to be a substitute descriptor for flyrock modelling. This will simplify the prediction techniques although launch angle is difficult to predict. Some insights for further R&D in this direction are also included in the paper