An Analysis of Hole Deviation and its Effect on Production

Abstract

An analysis of hole deviation and its effect on production at Chirano Gold
Mines Limited has been carried out. Chirano Gold Mines Limited employs
sublevel stoping and open stoping methods where production holes are
drilled in the form of rings. Complete control of borehole directions
sometimes was not obtained during drilling. This problem caused
shortfalls in the burden, spacing and hole depth parameters. The boretrak
instrument was used to measure the drill hole deviations at the stopes
during this study. The analysis was based on 29 holes in 5 rings which
recorded total deviations of 4.4 m, 1.9 m and 16.8 m in the burden,
spacing and hole depths parameters respectively. The result showed 31.2%
deviation in the burden, 2.8% deviation in spacing and 3.2% deviation in
the hole depth. The effect of the hole deviations on production was
portrayed by an increased output of 1965.85 t of materials representing
23% deviation from the planned. This result also showed that there would
be ore dilution which may decrease the mill head grade. This undoubtedly
would increase the cost of production of the mine through extra energy
requirement to blast and to process these waste materials. From the
results obtained, it was recommended that more boretrak surveys should
be carried out for informed decisions to be made by planners during the
preparation of the charge plans. Also, deviations in the toe burden should
be minimized by drillers using competent machines to drill accurately.