The V, V1, and V2 patterns are significantly better than row delays. Because of the lower hole loads, wider spacing at the moment of hole initiation, and inflight collisions of shattered rock during its movement, these lead to superior fragmentation. Increased wall stability is ensured by the delayed action of the back row’s holes, which decrease overbreak.
An equilateral triangle pattern with staggered hole drilling is the best pattern currently in use. This results in a roughly 1.16 drilled spacing to burden ratio. It has been noted that holes drilled on an equilateral triangle grid and fired using a V1 initiation sequence result in an effective spacing (Se) to burden (Be) ratio of roughly 3.5.
Compared to in-line patterns, drilling an equilateral triangle in a staggered pattern requires more operator expertise and oversight. An individual in charge clearly indicating the hole locations beforehand would be of great assistance to the drillers. Various delay schemes outlined above are shown in Fig.
