OFFICIAL calculation. Illustration 4; Coupling of the gas flow with discrete elements (Minchinton & Lynch, 1197). USE OF ELFEN PROGRAM FOR PRESPLIT CALCULATION WAVE THEORY As indicated in previous points, ELFEN simulates the detonation of explosive charges in a blasthole and the effect of gas pressures, expanding in the rock mass around the blastholes. To develop a presplitting model, it is necessary to have rock mass strength data with their respective structural sets and the properties of the explosive to be employed for this technique. Regarding respect to the parameters of the explosive, we need to know: VOD, density, effective energy, Relative Weight Strength (RWS), and Relative Bulk Strength (RBS). Under a Cpex model (Esen S, 2005; Minchinton, 2015; Louw, 1993), the pressure parameters are defined as a function of the rock strength and the confinement diameter. Since this method includes a confined explosive, it is necessary to make a modification to the detonation pressure, which is given by the following expression. = ൬ ൰ 2 (8) Where: P b = Pressure from blasthole. P d = Detonation pressure. dc = Explosive Diameter. db = Blasthole diameter. γ = Adiabatic Index. The explosion is modeled using a finite difference mesh and is considered a sudden expansion of a confined gas against the blasthole wall, which is treated as adiabatic due to
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