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At the forehead of the cross cut you can see some remains of the shot holes. Charlie noted that this is an interesting example of 'bad' drilling as you can see deep sockets left behind. When you are drilling a face for blasting all the shot holes need to be of equal depth. If a few are longer, then the charge in the deeper ones may not detonate correctly as the rock has no where to blast out due to the other holes not having gone as deep into the rock. The result is that you may end up with unexploded residue in the deeper shot holes. The danger stems from the fact that the hole drillers will be tempted to use the longer shot holes as a pilot for the next round, if there are explosive remains, then this can be very dangerous. |
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