6
accuracy. As previously mentioned, at least four aspects
affect the rebound and, eventually, shotcrete quality. The
data presented here is filtered with all the observations with
the recommended accelerator dosage between 6–8%. Also,
considering that typical rock mass or substrate in the obser-
vation location is similar. The other two factors are pure
nozzleman spraying techniques (nozzle angle and distance),
which are included in the developed nozzleman rating sys-
tem. The nozzlemen will be indicated with Arabic numerals
for confidentiality purposes.
Table 1 presents the nozzlemen, respective spraying
technique rating, and rebound measurements from both
rib and back spraying. With proper dosages, these eight
nozzlemen listed here at least measured the rebound twice
per category (rib/back), giving a minimum of 32 measure-
ments to develop this dataset. Further, Figure 7 provides
the scatter plot on the rebound percentage to the nozzle-
man rating. All the trends show similar correlations, where
a higher rating generally results in a lower rebound percent-
age. The fluctuation of the rebound percentage of the noz-
zle with a rating of less than 6.5 is high, which is reasonable
since they were still in the process of continual training and
needed to keep up with the consistency.
CONCLUSIONS
This study highlighted the benefits of targeted in-house
training and ongoing field support for improving shotcrete
application in underground mining operations. The pri-
mary outcomes include:
• Enhanced skills: Tailored training programs, com-
bining theory and hands-on practice, effectively
addressed skill gaps, leading to noticeable improve-
ments in nozzlemen performance.
• Reduced rebound: A clear inverse relationship was
observed between nozzlemen ratings and rebound
percentages, emphasizing the critical role of proper
spraying techniques in minimizing waste and ensur-
ing quality.
• Operational improvements: Better shotcrete applica-
tion reduced material waste, fewer rework require-
ments, and improved compliance with safety and
design standards.
These findings reinforce the value of continuous train-
ing and support for nozzlemen, paving the way for safer
and more efficient ground support practices in under-
ground mines.
Due to submission time limitations, Figure 6 will not be
available in the preprint version but will be available during
the presentation or can be sent upon request.
Figure 6. Typical dashboard for tracking nozzleman progress
Table 1. Summary of nozzleman rating and rebound
percentages from rib and back observations.
Nozzleman# Rating* Rib Rebound%
Back
Rebound%
01 6.06 14.89% 20.42%
02 6.18 12.33% 25.33%
03 6.39 17.12% 16.20%
04 6.46 20.21% 13.99%
05 6.68 13.98% 12.18%
06 7.14 10.10% 13.84%
07 7.21 10.23% 12.16%
08 7.23 11.25% 10.78%
*Accumulated nozzleman rating during April 2018
Figure 7. Rebound vs. nozzleman rating based on (a) rib observation and (b) back observation
accuracy. As previously mentioned, at least four aspects
affect the rebound and, eventually, shotcrete quality. The
data presented here is filtered with all the observations with
the recommended accelerator dosage between 6–8%. Also,
considering that typical rock mass or substrate in the obser-
vation location is similar. The other two factors are pure
nozzleman spraying techniques (nozzle angle and distance),
which are included in the developed nozzleman rating sys-
tem. The nozzlemen will be indicated with Arabic numerals
for confidentiality purposes.
Table 1 presents the nozzlemen, respective spraying
technique rating, and rebound measurements from both
rib and back spraying. With proper dosages, these eight
nozzlemen listed here at least measured the rebound twice
per category (rib/back), giving a minimum of 32 measure-
ments to develop this dataset. Further, Figure 7 provides
the scatter plot on the rebound percentage to the nozzle-
man rating. All the trends show similar correlations, where
a higher rating generally results in a lower rebound percent-
age. The fluctuation of the rebound percentage of the noz-
zle with a rating of less than 6.5 is high, which is reasonable
since they were still in the process of continual training and
needed to keep up with the consistency.
CONCLUSIONS
This study highlighted the benefits of targeted in-house
training and ongoing field support for improving shotcrete
application in underground mining operations. The pri-
mary outcomes include:
• Enhanced skills: Tailored training programs, com-
bining theory and hands-on practice, effectively
addressed skill gaps, leading to noticeable improve-
ments in nozzlemen performance.
• Reduced rebound: A clear inverse relationship was
observed between nozzlemen ratings and rebound
percentages, emphasizing the critical role of proper
spraying techniques in minimizing waste and ensur-
ing quality.
• Operational improvements: Better shotcrete applica-
tion reduced material waste, fewer rework require-
ments, and improved compliance with safety and
design standards.
These findings reinforce the value of continuous train-
ing and support for nozzlemen, paving the way for safer
and more efficient ground support practices in under-
ground mines.
Due to submission time limitations, Figure 6 will not be
available in the preprint version but will be available during
the presentation or can be sent upon request.
Figure 6. Typical dashboard for tracking nozzleman progress
Table 1. Summary of nozzleman rating and rebound
percentages from rib and back observations.
Nozzleman# Rating* Rib Rebound%
Back
Rebound%
01 6.06 14.89% 20.42%
02 6.18 12.33% 25.33%
03 6.39 17.12% 16.20%
04 6.46 20.21% 13.99%
05 6.68 13.98% 12.18%
06 7.14 10.10% 13.84%
07 7.21 10.23% 12.16%
08 7.23 11.25% 10.78%
*Accumulated nozzleman rating during April 2018
Figure 7. Rebound vs. nozzleman rating based on (a) rib observation and (b) back observation