571 VR= 7 x tπ xç 102 2 mm é#v + 4 x ∆π xç 54m2 m é#« (0.90ï ( 0.90ï) − …7 x tπ xç 102 2 ïï é#v + 4 x ∆π xç 54m2 m é#« This calculation yielded a value of VR≈9.0% considered acceptable to ensure effective cut without compromising contour stability. The critical separation between loaded holes was also estimated, which represents the maximum permissible distance without loss of continuity at the break of the massif. This was obtained using equation (4): Js=2 ( ∅ 2332D>)B2 çl l9éç; ! l << lé (4) Js = 2 ( 0.250 (t 1 2 7 1 .5 vt 1 1 0 0 0 0 v where: Ø effective = Effective diameter of the empty space E = Young's modulus of the rock mass (21.0 GPa) E0 = Reference Young's Modulus (17.5 GPa) REE = Relative energy of the explosive (ANFO = 100) The calculation determined a critical separation of 0.60m, a value that was taken as a maximum reference to define the drill mesh and the distribution of loaded holes around the cut. Finally, the design was validated through field tests focused on evaluating the effectiveness of the cut configuration under real operating conditions. These tests allowed adjusting the number of relief holes, as well as the delay times in electronic detonators, according to the load-relief ratio proposed by Holmberg, establishing the optimal conditions to maximize advance and minimize overbreak in 28-foot faces. Figure 36 – Proposed cut design considering a 102mm pilot center hole. 0.90m. 0.30m. 0.90m. R1 R2 R3 R4 R5 R6 R7 A1 A2 A3 A4
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