Pit & Quarry, May 2018
HOLE TIMING 3 MS RHYTHMIC TIMING PATTERN 42 ms 85 ms 130 ms 39 ms 82 ms 127 ms 36 ms 79 ms 124 ms 33 ms 76 ms 121 ms 30 ms 73 ms 118 ms 27 ms 70 ms 115 ms 24 ms 67 ms 112 ms 21 ms 64 ms 109 ms 18 ms 61 ms 106 ms 15 ms 59 ms 103 ms 12 ms 56 ms 100 ms 9 ms 54 ms 97 ms 6 ms 51 ms 94 ms 3 ms 48 ms 91 ms 0 ms 45 ms 88 ms Rhythmic timing sequence for a 3 millisecond delay without overconfinement blast A 12 millisecond delay may reduce this by 40 percent compared to the previous blast but only four holes would need to be fired for proper relief of the second row Advanced blast patterns can use a combination of these methods while providing additional relief or reducing the maximum ground vibration Under no circumstances should a 6 millisecond delay from row to row be used violating the main principle of confinement TAKEAWAYS Rhythmic timing practices are a modern tool for timing a blast to significantly reduce ground vibration from a blast These are normally used in accordance with signature hole techniques but proper understanding of how to use hole tohole and row to row delays need to be considered Without consideration of fragmentation throw and confinement rhythmic Source Precision Blasting Services timing could produce much worse results than previous blasting practices Shooting faster is not always beneficial and has not proven to reliably and repeatedly raise frequency without dramatically raising peak particle velocity Instead proper timing to reduce confinement and reduce the peak particle velocity of a blast should be implemented with an appropriate rhythm of holes firing to ensure no clumping of blastholes cause higher than necessary vibration P Q Anthony Konya is an explosive engineer for Precision Blasting Services who consults around the world in rock blasting and vibration from blasting Calvin J Konya is the president of Precision Blasting Services and director for the Academy of Blasting and Explosive Technology consulting and training worldwide in rock blasting vibration and emulsion manufacturing FINES RECOVERY www kpijci com pitandquarry com May 2018 PIT QUARRY 33
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