Flyrock in Surface Mine Blasting: Understanding the Basics to Develop a Predictive Regime

Flyrock is one of the most contentious issues in bench blasting. Unlike ground vibrations, flyrock has the propensity to cause fatality and severe injuries. Although the kinematic equations present a basis for the estimation of flyrock distance, these suffer from the drawback of ignoring the post-release effects of trajectory motion in air. Predictive models that are based on such equations not only suffer from this anomaly, but also fail in flyrock distance prediction due to the gross approximations of initial velocity calculations and shape of the fragments.

This article discusses the flyrock phenomenon, causative factors and their use in developing prediction models. Different predictive models, namely empirical and semi-empirical are reviewed and the drawbacks highlighted. The principal causative factors of flyrock namely blast-hole pressure, time of blasting impact and post-release corrections are discussed with their relevance. The study culminates into a futuristic comprehensive flyrock distance prediction methodology to predict the blast danger zone along with the probability and risk associated with flyrock.