575 5. CUT REDESIGN Based on the results obtained in the cut tests, and with the aim of optimizing the efficiency of the firing, the need to redesign the cut scheme arises. The redesign of the cut consisted of reducing the concentration of specific energy associated with the central hole of 102 mm in diameter, redistributing it by incorporating five 54 mm break holes. This modification made it possible to decouple the explosive charge originally concentrated in a single largediameter hole, generating a more homogeneous distribution of the stress field around the relief holes. From the point of view of fracturing mechanics, the new configuration improves the interaction between the break holes and the relief holes, favoring a progressive release of energy, greater efficiency in the creation of the free face and an increase in the effective advance per shot. In addition, the reduction of the diameter of the central bore decreases the confined detonation pressure and, consequently, the magnitude of the air wave generated. This helps mitigate overpressure in underground workings and reduces the likelihood of damage to auxiliary installations, such as water networks, compressed air and ventilation sleeves. As part of this evaluation, the possibility of increasing the ratio of available empty volume was analyzed, going from the initial value of 9% to 14%. VR= 6 x tπ xç 102 2 mm é#v + 5 x ∆π xç 54m2 m é#« (0.71ï ( 0.71ï) − …6 x tπ xç 102 2 ïï é#v + 5 x ∆π xç 54m2 m é#« Figure 5 – Final cut design considering a 54mm pilot center hole and reduction of the area of the first break quadrant. i. Cut Simulation Once the redesign of the cut scheme was completed, an energy halo simulation was carried out, with the aim of evaluating the spatial distribution of explosive energy in the new configuration. 1.0m. 0.30m. 1.0m.
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