The Journal of Explosives Engineering - January/February 2015 - 34

Table 2. Seismograph distance from blast and data.

Figure 4. First dozer shot.

pattern to get the 5,700 ft (1,737 m) down to the 5,680 ft
(1,731 m) elevation to fully free face the panel shot. Since this
shot had less than half the explosives per hole than the 40 ft
(12 m) drop it was decided to shoot all 402 holes (11 dead)
in one shot. The blast shot on Jan. 2, 2013, outlined in red
is shown in figure 3. The closest hole to the dozer was 158
ft (48 m) and gave a seismic reading of 1.520 in/s (38.608
mm/s) max at 22.2 Hz and the lowest frequency 13.0 Hz at
1.280 in/s (32.512 mm/s). The dozer scans did not show any
significant movement near or around the dozer. This blast had
less ground vibrations than the first shot that was similar in
distance but this shot had less than half the pounds per delay.
This blast had a lot of stemming ejection and was also quite
violent as can be seen in figure 7. Quite a bit of material was
cascaded down the side of the highwall and there was some
fly material that could have hit the dozer if it had been closer.
There was a little bit of snow that fell down the high wall in
front of the dozer but no actual material fell.
Shot number five next to the dozer was the first panel shot.
There was a failure in the wall that split the pattern up into
two shots. In figure 3 the gap in-between the pink and teal
shots show the area that failed. The pink pattern (Jan. 24,
2013) was the panel shot we shot first. The blast had 53, 63
ft (19 m) holes, and 700 lbs (318 kg) of explosives per hole.
The closest hole to the dozer was 219 ft (67 m). This shot gave
a PPV of 1.880 in/s (47.752 mm/s) at 13.4 Hz which was the
lowest frequency. The before and after dozer scans came back
negative for significant movement. Figure 8 shows the before
34

and after scans. All of the scans looked very similar except for
one so only two scans are shown in this article. In the scan
anything that is in blue is up to 1 ft (0.3 m) of material gain,
gray is zero movement, and orange is up to 1 ft (0.3 m) of lost
material. The green color means it went out of the range of
-1 ft (-0.3 m) to 1 ft (0.3 m). The scan shows that the material
near the dozer was basically unaffected. The material that is
right next to the free face shows a little bit of loss but it was
right in front of the blast and it was expected to see a little bit
of movement there. The material next to where the blast was
located was unaffected. This means that this is a safe distance
(140 ft/43 m) from the high wall to put the blast once we get
to patterns directly behind the dozer. Figure 9 shows the
fifth blast. This blast had the least amount of fly material and
only one stemming ejection that was from a hole plugging
during stemming.
Shot number six was the second panel shot next to the
dozer. The blast had 12, 63 ft (19 m) holes (0 dead), and 700
lbs (318 kg) of explosives per hole. The teal pattern (Feb. 1,
2013) in figure 3 shows shot number six. This pattern was
only 108 ft (33 m) away from the dozer and had more burden
than designed due to the failure. This pattern also had some
short holes in the middle of the pattern. This shot gave a PPV
greater than 5 in/s. Unfortunately the seismograph was set to
a max of 5 in/s so data was not received. The scan showed little to no movement on and around the dozer. This was a good
sign that the dozer was pretty well set in the catch bench and
as long as the material in the catch bench did not get casted

The Journal of Explosives Engineering

January/February 2015

The Journal of Explosives Engineering - January/February 2015

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