572 ii. Holes Deflection Analysis The execution of 8-meter horizontal drilling in development faces represents a significant technical challenge, due to the possible deviation of the holes from their theoretical trajectory. Despite the use of high-precision equipment and the application of good operational practices, there are geological factors inherent to the rock mass, such as fractures, planes of weakness or abrupt lithological transitions, which directly influence the final direction of the holes. These deviations affect the geometry of the blast face, altering the symmetry and distribution of the drilling scheme at the bottom of the face. Consequently, it is difficult to execute an efficient blasting sequence, and areas of low fragmentation, overbreak or even unexploded holes (misfires) can be generated, which negatively affects the performance of the cycle. Therefore, a systematic process of measurement and analysis of the real trajectory of the cut holes was implemented, with the aim of: • Quantify angular and linear deviations from the designed mesh. • Identify deviation patterns associated with geological conditions or recurrent operating factors. • Adjust the detonation sequencing, allowing the assignment of differentiated delay times per hole, according to its actual location, and thus recover the logic of the shot. Figure 2 presents a scatter plot representing the measured trajectories of the holes, compared to their theoretical orientation. Figure 3 also shows the percentage of deviation associated with each drill, key information for the calibration of the blasting design and the optimization of the overall performance of the face. Figure 2 – Dispersion of drilled holes at cut. Figure 3 – Percentage of deviation by number of holes. R1 R2 R3 R4 R5 R6 R7 A1 A2 A3 A4 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 Variation Y (m) Variation X (m) 6 5 0 55% 45% 0% 0% 10% 20% 30% 40% 50% 60% 0 1 2 3 4 5 6 7 0.0 - 0.25m. 0.25 - 0.5m. 0.5 - 1m. Percentage N °Holes Number of deviated drill holes
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