4
Table 1. Boretracking data collected from pre-split holes showing spectrum of average angle
of inclination from 14.8° to 18.7° and corresponding changes in design length (i.e., depth)
and bottom walk from collar (i.e., horizontal distance between collar and bottom of pre-split
hole).
Face
Height
(ft)
Angle of
Inclination
(’)
Final Hole
Length (ft)
Bottom Walk
from Collar
(ft) Comments
45 14.8 46.5 11.9 Top bench: Approx. 3ft forward walk
variance between holes 45 15.0 46.6 12.1
45 18.7 47.5 15.2
90 14.8 93.1 23.8 Bottom bench: Approx. 7ft forward
walk variance between holes 90 15.0 93.2 24.1
90 18.7 95.0 30.5
Figure 4. Image of pre-split hole traces on 90ft bench face showing significant deviation on
bottom portion compared to the top 45ft (13.7m)
Figure 5. Cross-section of traditional trim-blast design with the addition of pre-split holes
deviation spectrum
Table 1. Boretracking data collected from pre-split holes showing spectrum of average angle
of inclination from 14.8° to 18.7° and corresponding changes in design length (i.e., depth)
and bottom walk from collar (i.e., horizontal distance between collar and bottom of pre-split
hole).
Face
Height
(ft)
Angle of
Inclination
(’)
Final Hole
Length (ft)
Bottom Walk
from Collar
(ft) Comments
45 14.8 46.5 11.9 Top bench: Approx. 3ft forward walk
variance between holes 45 15.0 46.6 12.1
45 18.7 47.5 15.2
90 14.8 93.1 23.8 Bottom bench: Approx. 7ft forward
walk variance between holes 90 15.0 93.2 24.1
90 18.7 95.0 30.5
Figure 4. Image of pre-split hole traces on 90ft bench face showing significant deviation on
bottom portion compared to the top 45ft (13.7m)
Figure 5. Cross-section of traditional trim-blast design with the addition of pre-split holes
deviation spectrum