1862 Vibration data were collected using seismographs equipped with triaxial geophones, which recorded particle velocity waveforms. Sensors were strategically installed at the undercut level across multiple nearfield (typically 10–50 m) and far-field (>50 m) locations relative to the blast source. Measurements of peak particle velocity (PPV) and corresponding scaled distances enabled regression analysis (log-log plot of PPV versus scaled distance) to derive site-specific attenuation constants (K and α) for the ground vibration attenuation law. This followed the widely accepted USBM scaled-distance form: PPV = K . (SD) @É =K . (Ö Ñ Ü)@É (1) Where: PPV: Peak-Particle Velocity (mm/s) SD: Scaled distance D: Distance from the blast source (m) Q: Maximum charge per delay (kg) K: Propagation coefficient α: Attenuation coefficient (range 0.5 - 2) 2.2.1 Ground vibration attenuation law From the blast vibration monitoring carried out at the María Teresa mine, a set of 75 seismographic records obtained was grouped (Figure 4), from which the following scatter plot was obtained: Figure 4. PPV values registered by the seismographs at María Teresa. Source: Orica Blast Engineering From the graph above, by plotting the trend line of the data distribution with respect to the scaled distance, a general ground attenuation law is obtained: PPV = 1909.83 x( ã D Q )@#.<! This attenuation law has a correlation coefficient (R²) of 0.87, which is acceptable. However, for each peak particle velocity (PPV) value estimated with this model, the probability of not exceeding the established limit will be 50%. This scatter results in moderate correlation in direct fits (R² typically 0.700.90) and can cause the fitted attenuation exponent α to deviate from the value that best captures the observed far-field decay.
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