Modeling Blast-Induced Fragmentation of Jointed Rock Mass Using Voronoi Discrete-Element Method

Abstract

Pattern design and management of blasting in open pit mining have been constantly of great interest to many mining engineers so as to reach an appropriate degree of fragmentation for loading, hauling, and crushing systems. Inappropriate fragmentation incurs extra costs in the form of secondary blasting, disruptions in the loading and hauling process, and so forth. To tackle this problem, it is necessary to predict the blast-induced fragmentation. Numerous methods have been proposed by many researchers to predict fragmentation. Regarding technological advancements, and with the advent of numerical codes, the restrictions of empirical methods for the prediction of blast-induced fragmentation can be overcome. The present study developed a model for the estimation of blast-induced fragmentation using a discrete-element method coupled with image processing techniques. In the numerical model, Voronoi elements were used to simulate microcracks of rock materials. Preexisting joints were also present in the model; prior to the blasting, their information was elicited in the area of interest (the Hegmatan limestone mine, Iran). After the blasting, the real fragmentation and modeled fragmentation were compared using image processing software. The results obtained from the numerical modeling were in good agreement with the real data, validating the simulation procedure. Hence, the Voronoi discrete-element method coupled with the image processing technique is appropriately capable of modeling the blasting-induced fragmentation in a discontinuum. Finally, the influence of different parameters, namely delay, presplitting, preexisting joints, discontinuity spacing, and spacing-to-burden ratio, on fragmentation indices were numerically simulated and investigated. The results showed that the lack of delay increases D50 of fragments from 32.57 to 95.94 cm, the application of presplitting negligibly affects fragmentation, and the preexisting joints in the study area enhanced the fragmentation performance.