The Journal of Explosives Engineering - January/February 2015 - 37

from the dozer. This blast was done while the blasting engineers were at the 2013 ISEE conference and the seismograph
monitors were improperly set up and a valid reading was not
obtained. The video was also missed, but the before and after
dozer scans showed little to no movement of the dozer and
the surrounding material. This shot was slightly north of being behind the dozer. Shot 8 was the last dozer shot needed
for equipment space to retrieve the dozer and was slightly
south of being behind the dozer. This shot had 53, 63 ft (19
m) holes (0 dead), and 700 lbs (318 kg) of explosives. This
shot gave a PPV of 8.80 in/s (223.52 mm/s) at 28.4 Hz with
the lowest frequency of 4.7 Hz at 6.00 in/s (152.4 mm/s). The
scans showed little to no movement of the dozer or the material around it. Figure 12 shows the eighth dozer blast. This
shot had some stemming ejection that was caused by using
drill cuttings and holes plugging.
After the eighth shot the bench was down to the dozer
blade elevation and there was enough room for equipment to
operate. The 50 ft (15 m) buffer zone ended up being easy to
dig. This was due to the shock wave from the blast creating
micro fractures in the rock. This was expected, but was not
expected to work as well as it did. Figure 13 shows the dozer
after final excavation of the buffer zone. The removal of the
dozer was done by strapping onto the tool bar with the shovel
and digging the material out from under it with a backhoe
then dragging it to more stable ground. The dozer had no
blast damage and all of the glass was intact. Once the fluids
were changed this dozer was out in the pit again working.

Conclusion
The dozer rescue using blasting to excavate the bench to
the level of the dozer was a success. Although vibrations were
significantly more at the dozer with the panel shots than the
drop cuts, using regular production blasting design would
have caused even more vibrations in the same location and
would have casted material onto the dozer and disturbed the
catch bench material that the dozer was sitting on, resulting
in dozer loss. No vibration limit was established due to only
being able to measure up to 10 in/s (254 mm/s) and the use
of laser profiles to track movement. The accuracy of the laser
profiles was around 2 inches (50 mm) so if the laser profile
showed a movement of 3 inches (80 mm) or more a design
change for the next shot would have been implemented. Using the technique of increasing powder factor by decreasing
burden and spacing and increasing face height and casting
the rock away from the dozer did significantly reduce the impact of blasting near the dozer.

References
Unknown. (2012). Service Manual for a Cat D10 Dozer. Peoria, IL,
United States of America: Caterpillar Inc.
Unknown. (2012). Orica Pocket Blast Guide. Melbourne, VIC,
Australia: Orica Mining Services.
Walker, J. (2010). AutoCAD Civil 3D. San Rafael, CA, United
States of America: Autodesk.

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White Industrial Seismology..................................3
January/February 2015

The Journal of Explosives Engineering

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The Journal of Explosives Engineering - January/February 2015

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