Environmental and Site Controls: Vibration, Flyrock, Noise, Dust
Blasting affects the surroundings through ground vibration, airblast (noise and overpressure), flyrock, dust and fumes. Candidates must understand the controls for each and the monitoring that demonstrates compliance.
Ground vibration is described by peak particle velocity (PPV) and frequency; it is influenced by charge weight per delay, distance and geology. The scaled-distance approach relates charge weight per delay and distance to predicted vibration. Reduce charge weight per delay, use delays, and increase distance to control vibration. Airblast is controlled by good stemming, confinement, and avoiding exposed detonating cord or unstemmed holes.
Flyrock is controlled by adequate burden and stemming, correct design, and clearing the exclusion zone. Dust and fumes are controlled by water, dust suppression, appropriate explosive selection and ventilation, especially underground. Monitoring (seismographs, airblast monitors) provides records; exceedances trigger investigation.
Traps: confusing PPV with airblast overpressure; assuming total charge rather than charge per delay governs vibration; and forgetting that weather (wind, temperature inversion) affects airblast and fume dispersion.
Rule of thumb: vibration is governed by charge weight per delay and distance; airblast by confinement and stemming.
Worked example: if vibration exceeds a limit, reduce the maximum charge weight per delay (more delays, smaller charges) before considering changing the whole design.