Blasting is an essential component of fragmentation and material extraction operations in both surface and underground mining. Successful completion of any safe and effective blast operation requires proper initiation control, circuit testing and verification, and complete compliance with regulations. Blasting hazards like misfires, flyrock, and early detonation were previously associated with poor timing and uncontrollable environmental conditions. Introduction of modern digital testing technologies, use of electronic detonators, and establishment of safety regulations like MSHA and WorkSafeBC safety regulations have greatly improved the safety of mining operations. This article reviews necessary testing devices, safety operations and misfire management methods for miners.
Present-day blasting involves the use of special equipment to ensure the integrity of the circuit before ignition. Electric circuits should be tested using blasting galvanometers or multimeters that prevent firing of the electric circuit by limiting the current flow to 0.05 amperes. These instruments can detect open circuits, shorts, and ground current leaks. Electronic detonators are used instead of pyrotechnic delays as they include circuits and capacitors that provide accurate timing and diagnostic check before the blast. Specialized tools include Digital Blast Ohmmeters, Circuit Interrupters, Shot Exploder Energy Meters, and VOD timers.
Safe blasting needs careful handling in terms of borehole loading and shot firing. It is important that the depth of the borehole should be measured and the borehole should be stemmed using noncombustible material like crushed rock to avoid flyrock and airblast. Electrical leg wire and lead lines should be shunted until it is finally hooked up to avoid stray current, static electricity, and radiofrequency energy. The unnecessary people should be cleared off the site, access control should be ensured and warning signals should be provided prior to shot firing. The work can continue only after inspection and confirmation that there are no hazards on the site.
A misfire occurs due to circuit cut-off, lace-up errors and water degradation. In case of suspected misfire, it is very essential that one has to wait for specific periods before entering into the blasting area: 15 minutes for electrical, electronic or shock tube, 30 minutes for safety fuse and 1 hour if explosives are assumed to be burning. Inspections should also include checks on the face and muckpile to detect bootlegs, loose wires, and undetonated explosives. The safe handling of misfire could be done by water flushing and repriming of the misfire.
Blasting that is both effective and safe is only possible through a combination of good testing equipment and proper loading procedures. This ensures that unnecessary dangers are avoided while at the same time optimizing the process of fragmentation within the mine sites.
