OFFICIAL Table 2; Properties of the explosive used in the modeling. PROPERTIES OF THE EXPLOSIVE Nominal Density(g/cm3)(1) 1.15+/- 5% Energy (Heat of formation - MJ/kg) 3.47 Effective Energy (MJ/kg)(2) 2.41 Relative Effective Energy (REE)(3) Relative strength of weight 105 Relative Volume Strength 151 Typical VOD (km/s)(4) >5.0 Gas volume (l/kg) 903 CO2 (kg/t)(5) 190 STUDY METHODOLOGY A rock mass model was developed in plan view, incorporating existing structural planes. Additionally, eight blastholes with a 5-inch diameter were arranged with spacings of 1.2 m, 1.5 m, and 1.8 m; this setup was repeated for each explosive diameter to generate the presplit fracture. To simulate field conditions, an additional 10 5/8-inch diameter blasthole, loaded with a low-density explosive, was positioned 12 meters from the presplit line (see Figure 1). Ten virtual geophones were installed as numerical control points to measure the Peak Particle Velocity (PPV) in mm/s as the wave propagates. These virtual geophones are distributed into two groups — five located before and five after the presplit line — to record the vibrational state induced by the detonation. The modeling sequence consisted of the following steps: • Generate a mesh between structural planes at 0.5 m intervals to represent a moderately fractured rock mass. • Initiate the presplit blastholes first to generate a tensile plane. • After a 70-millisecond delay, detonate the 10 5/8" borehole loaded with lowdensity explosive. • Record the particle velocities (PPV) at each geophone and develop a vibration model to estimate the attenuation capacity provided by the presplit fracture. The resulting values will be compared against traditional benchmarks used in metallic mining to evaluate presplit effectiveness (see Table 3). However, these values are strictly referential, as the results must be validated through field inspections and on-site observations.
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