Endbreak off the end of a shot usually results from one of two reasons. The local geologic structure can promote extension of cracks off the end of the shot. This can be corrected by shortening the spacing distance on the end to the nearest production holes thereby causing the hole to function and respond in a different fashion.
Endbreak can also be caused by having improper timing on the perimeter holes, If the timing is too fast, blastholes will tend to sense a much larger than normal burden thereby either rifling and causing uplift, or by cracking back into the formation.
The problem of timing can be corrected in the same manner as that described for backbreak. Longer delay times, such as those which were previously discussed in Chapter 6, can be used on the end holes, allowing time for the center portion of the blast to move out. This produces additional relief before the end holes fire.
