Effect of ejected particle shape and geometry on the projectile behavior of flyrock: A stochastic analysis

Abstract

Flyrock is a critical blast-induced hazard in open-pit mines that can cause injuries, fatalities, and damage to surrounding structures. Although various methods have been proposed to predict flyrock, the random nature of the phenomenon limits the effectiveness of precise deterministic models. Statistical stochastic simulation can therefore provide a more logical approach. In this study, a MATLAB-based stochastic model was developed using a cross-sectional representation of the blast block. Random positions were assigned to particle starting points, while particle dimensions, geometry, velocity, and projection angle were randomly generated. Aerodynamic coefficients were determined from particle dimensions and geometry, and the trajectory of each particle was simulated. The probability of particle breakage upon ground impact was then evaluated. For particles that did not break, rebound trajectories were simulated until complete stoppage. The resulting particle trajectories enabled estimation of muck pile geometry, maximum horizontal and vertical flyrock distances in both forward and backward directions relative to the blast block, and the percentage of particles breaking upon impact. The model was validated using drilling and blasting data from 53 blast blocks in a mine in Lorestan Province, Iran, including measurements of maximum horizontal flyrock distance and average fragmented-rock size. After adjusting the projectile velocities, the simulated maximum horizontal flyrock distance and average fragmented-rock size showed good agreement with the corresponding field measurements. The results demonstrate that the developed probabilistic model can predict key blast outcomes while accounting for multiple real-world parameters.