Mining Geology, Mine Development and Surveying · Mine Development · 2 marks · Numerical answer
Each hole in the displayed bench-blast pattern contains49 kg explosive. Hole labels give delay times in milliseconds. Using the supplied scaled-distance/PPV relation, find PPV at100 m in mm/s to two decimals.
The largest simultaneous group contains two holes, so maximum charge per delay is98 kg. Square-root scaled distance is SD=100/√98≈10.1015 m kg⁻¹/². The supplied relation gives PPV=250(SD)⁻¹·⁵≈7.79 mm/s. Use the simultaneous-delay group rather than the total charge of the entire pattern.
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